Volume 42,2025 Issue 4

• Development and Evaluation of Pressure Sensitive Self-healing Plugging Agent for Drilling Fluid

  2025(4):571-576, DOI: 10.19346/j.cnki.1000-4092.2025.04.001

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  Abstract:

  In view of the technical problems of long swelling time and weak water dilution resistance of gel plugging agent in drilling engineering，the pressure sensitive self-healing plugging agent CMC-DAS was prepared from carboxymethyl chitosan （CMC）and dialdehyde starch（DAS）by cyclic freeze-thaw method. The molecular structure and particle size distribution of CMC-DAS were characterized and determined respectively by means of infrared spectroscopy and laser particle size analyzer，and its swelling performance，water dilution resistance performance，pressure-sensitive self-healing performance，nano-micron pore sealing performance，pressure penetration performance and microscopic morphology were investigated. The results showed that after high-temperature aging，CMC-DAS particles were still in nano-micron monodisperse state. The water absorption swelling expansion of CMC-DAS increased first and remained stable，the swelling equilibrium time was 7 h，and the water dilution resistance was controlled within 10% after 72 h. When the pressure increased from 2.5 MPa to 10 MPa，the fracture strength of CMC-DAS increased from 0.1131 MPa to 0.3516 MPa，and the elongation at break increased from 135% to 260% . When the addition amount of CMC-DAS was 0.5%，the reduction rate of core permeability reached more than 80%，exhibiting excellent plugging performance. By comparing the microscopic morphology of CMC-DAS on the core surface before and after aging at 160 ℃ for 16 h，the gel particles could be squeezed and deformed and enter the pores and fractures of the core，and a smooth and flat isolation film was formed on the surface，which played a positive role in improving the stability of wellbore.

• Preparation and Field Application of a Lubricating and Plugging Agent for Drilling Fluids

  2025(4):577-583, DOI: 10.19346/j.cnki.1000-4092.2025.04.002

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  In response to the economic exploration and development needs of shale oil and gas，a lubricating and plugging agent SMLP-1，suitable for 80 —120 ℃ well sections prone to wellbore instability，was developed using Y # asphalt，petroleum resin， oil-soluble phenolic resin and other compositions as the oil phase matrix material，graphene oxide as the grafting particle，X# white oil as the dispersed phase，and using silicone modifier and organic amine modifier to modify. The lubricating and plugging effect of SMLP-1 in the drilling fluid system and its impact on drilling fluid performance were evaluated through the analysis of drilling fluid performance. The action mechanism of SMLP-1 was demonstrated through characterization methods such as scanning electron microscopy（SEM），infrared spectroscopy，and thermogravimetric analysis，and field tests were conducted. The results showed that SMLP-1 had good dispersibility in the drilling fluid，forming stable oil-in-water droplets in the system. After adding SMLP-1， the API filtration loss of the base fluid did not change significantly，but the high-temperature and high-pressure filtration loss was significantly reduced，indicating that SMLP-1 had a strong effect on reducing high-temperature and high-pressure filtration loss. After adding 1% SMLP-1，the lubrication coefficient decreased by 16% at room temperature，and after 16 hours of hot rolling at 150 ℃，the lubrication coefficient decreased by 43%. SMLP-1 could effectively plug shale pores and had good waterproofing and anti-water invasion effects，with significant inhibition on the hydration and dispersion of bentonite. SMLP-1 had been successfully tested on-site in the Qinye MN03HF well，with a cumulative footage exceeding 1000 m. After the addition of SMLP-1，the high-temperature and high-pressure filtration loss decreased from 13.2 mL to 8.6 mL，and the lubrication coefficient reduction rate was 30%. This not only reduced the intrusion of free water into the formation from the drilling fluid，improved the plugging ability and wellbore stability of the drilling fluid，but also enhanced the lubricity of the drilling fluid，ensuring safe drilling in complex well sections and achieving good application results.

• Molecular Simulation Study on Shear Adsorption of PAMAM Hyperbranched Polymers at Fe interface

  2025(4):584-593, DOI: 10.19346/j.cnki.1000-4092.2025.04.003

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  Hyperbranched polymers，with their unique three-dimensional topological structures and abundant active terminal groups，have shown significant potential in enhancing the lubricating properties of water-based drilling fluids. However，the structure-activity relationship between their molecular configurations and lubricating performance remains unclear，which hinders the development of new high-performance additives based on spatial configuration design. In this study，based on the boundary lubrication theory，the structural characteristics of multi-generation（G1—G5）PAMAM molecules and their adsorption behavior at the metal iron（Fe）interface were systematically studied by quantum chemistry and molecular dynamics methods. The structural changes of PAMAM molecules at the Fe interface during the shearing process were analyzed. The results indicated that PAMAM hyperbranched macromolecules possessed hierarchically distributed N and O active atoms，with the central N atom exhibiting the strongest electron-donating ability，followed by the terminal N atoms. As the generation increased up to G5，the three-dimensional structural stability of PAMAM molecules improved，with enhanced entanglement of molecular chains at the core and "claw-like" distribution of outer branches，which enhanced multi-point adsorption capabilities. During the adsorption of PAMAM molecules on Fe surfaces，atomic distribution extended along the interface and its normal direction，while shear promoted the aggregation of PAMAM molecules at the Fe interface，forming a transfer film that contributed to the formation of a robust lubricating layer. Finally，a lubrication enhancement model for hyperbranched polymers was proposed，which should provide theoretical support for the design of high-performance hyperbranched polymer additives.

• Drag Reduction，Sand Carrying and Rheological Properties of Medium and High Viscosity Slick Water Fracturing Fluid Based on Hydrophobically Associating Polymer

  2025(4):594-606, DOI: 10.19346/j.cnki.1000-4092.2025.04.004

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  In view of the technical bottleneck that the traditional slickwater fracturing fluid is difficult to meet the drag reduction and sand carrying performance at the same time in the middle and high viscosity range，a new hydrophobically associating polymer fracturing fluid was prepared，and its drag reduction and sand carrying performance and rheological properties were tested in the middle and high viscosity range. At the same time，the potential correlation mechanism of polymer structure-rheology-drag reduction and sand carrying was explored. The results indicated that when the concentration of hydrophobically associating polymer exceeded the critical associating concentration（CAC），the drag reduction rate of the fracturing fluid system increased by more than 10%，and the proppant settling rate decreased by 30%. The synergistic optimization of enhanced proppant-carrying performance and maintained drag reduction efficiency could be achieved by increasing the content of hydrophobic monomers. Rheological data revealed the mechanism of key rheological parameters：the sand-suspending performance followed a power-law relationship with the elastic modulus（G'）as v = aG'^b，and the dag reduction efficiency exhibited an exponential relationship with the first normal stress difference（N₁）as DR = a + Ae^{[-0.5(N₁-x/w)]}. Constructing a high-efficiency drag reduction and proppant-carrying system using hydrophobic associating polymers enabled dual improvements in drag reduction and proppant carrying. The established rheological regulation model provides a theoretical basis for the molecular design and performance optimization of associating polymer fracturing fluids.

• Dynamic Degradation Characteristics of Guar Gum During Fracturing Flowback Fluid Treatment

  2025(4):607-613, DOI: 10.19346/j.cnki.1000-4092.2025.04.005

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  Aiming at the problem of poor effectiveness of reagents when treating high-viscosity fracturing flowback fluid，the degradation experiments using chemical oxidation method，hydrolysis acidification method and enzymatic hydrolysis method were designed. Dynamic parameters such as viscosity，molecular weight，particle size distribution and the concentration of degradation products were measured through viscosity analysis， particle size detection， gel permeation chromatography， and sugar concentration detection. The results showed that when the guar gum was degraded with 10 g/L sodium hypochlorite using chemical oxidation method，the optimal viscosity reduction time was 30 min，and the viscosity was decreased to 4.22 mPa·s，while guar gum degradation remained incomplete，the particle size of the aggregates was greater than 2 μm and the degradation products with molecular weights was around 80×10⁴ Da，predominantly containing saccharide structures. Moreover，the increase of the sodium hypochlorite concentration could not enhance obviously the viscosity reduction effects. When the guar gum was degraded with 10 g/L activated sludge using hydrolysis acidification method，the viscosity reduction rate was slow during the initial stage of hydrolysis acidification but the complete viscosity reduction was achieved within 24 h. The particle size of the aggregates was approximately 0.21 μm and the molecular weights of the degradation product exhibited two-stage decline patterns，demonstrating "long-term effectiveness" characteristics. When the guar gum was degraded with 10 mg/L enzyme using enzymatic hydrolysis method，the viscosity was decreased to 5.43 mPa s within 10 min and the complete viscosity reduction was realized within 15 h. The molecular weight of the guar gum decreased to 160×10⁴ Da within 0—2 h，and the guar gum was completely transformed into small-molecule saccharides after 15 h. At the same time，the aggregates was approximately 0.19 μm. Compared with the control group，enzymatic hydrolysis caused minimal changes in chemical oxygen demand （COD） contributed by saccharides and total solution COD， indicating that the enzymatic hydrolysis reaction had strong selectivity and outstanding viscosity reduction effect on macromolecular guar gum，which was a better choice for the pretreatment process of fracturing flowback fluid.

• Strong Association Double Network High Temperature Resistant Cross-linked Acid Based on Double Modified Nano SiO₂

  2025(4):614-621, DOI: 10.19346/j.cnki.1000-4092.2025.04.006

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  Aiming at the problem of insufficient temperature resistance and retarding performance of conventional acid in acid fracturing of deep-high temperature carbonate reservoirs，S-ANS was prepared by amination and sulfonation of nano-SiO₂ ，and then amphoteric acid-resistant and thickening nano-hybrid polymer S-ANS-HAPAM was obtained using S-ANS，acrylamide（AM）， acrylic acid（AA），sodium 2-acrylamide-2-methylpropanesulfonate（AMPS）and cetyldimethylallylammonium chloride（DMAAC） as main raw materials. The polymer structure was characterized by Infrared spectroscopy，X-ray photoelectron spectroscopy，and other methods. A 20% hydrochloric acid cross-linked acid system was prepared using S-ANS-HAPAM as a thickener. The rheological properties，drag reduction properties and gel breaking properties of the prepared cross-linked acid were evaluated，and the thickening mechanism of the cross-linked acid was analyzed. The results showed that the viscosity of the cross-linked acid-based solution increased with the increase of the dosage of thickener S-ANS-HAPAM at the of temperature of 25 ℃ and at the shear rate of 170 s^-1，and the viscosity of the base solution was 96 mPa s when the S-ANS-HAPAM dosage was 0.7%. The viscosity of the cross-linked gel with 0.7% thickener and 0.7% cross-linking agent was above 37 mPa·s after shearing for 120 min at the temperature of 180 ℃ and at the shear rate of 170 s^-1，indicating that the S-ANS-HAPAM cross-linked acid system had good temperature and shear resistance under strong acidic and high temperature conditions.During the frequency scanning process，the storage modulus G' of the gel was always higher than the loss modulus G''，meaning that the structural stability of the obtained gel was significantly better than that of the conventional polyacrylamide gel. SEM analysis confirmed that the formation of a physical-chemical dual network structure after crosslinking，and the mechanism of good viscoelasticity，temperature resistance and shear resistance of the crosslinked acid gel was also explained. The gel breaking time of the crosslinked acid gel at 120 ℃ and 150 ℃ was only 3 h，and the residue content was as low as 179 and 129 mg/ L，respectively，which was much lower than the standard of SY/T 5107-2016“Water-based Fracturing Fluid Performance Evaluation Method”for residue content（600 mg/L）. The cross-linked acid system achieved stable thickening and slowing performance at 180 ℃ and excellent low residue breaking properties through the synergistic effect of hydrogen bonding physical network introduced by double modified nano SiO₂ and zirconium cross-linked chemical network，providing an efficient and low damage solution for deep acid fracturing of ultra-high temperature carbonate reservoirs.

• Waterflood Scaling and Acidification Scaling Behavior and Influencing Factors in Ultra-low Permeability Reservoir

  2025(4):622-630, DOI: 10.19346/j.cnki.1000-4092.2025.04.007

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  The inorganic scale formed due to the incompatibility between injected water and formation water entangles with crude oil and particles in the pores and deposits，reducing the flowable space of the pore throats. The effect of single acidification is not ideal，restricting the water injection development of the oilfield. In order to improve the effect of the injection measures，it is necessary to clarify the characteristics of scale formation during water injection and the characteristics of scale dissolution during acidification. Taking the Chang X ultra-low permeability reservoir in Changqing oilfield as an example，through the visualization of the reservoir 's own fluid，external fluid and acidification times and the core simulation experiment scheme，combined with the changes of scale and injection pressure in the pore throat，the scale size，distribution change and sedimentary morphology characteristics at different positions were analyzed，and the changes of plug dissolution，migration and deposition during acidification were revealed. The results showed that in water injection development，due to the influence of water-type incompatibility，the inherent oil of the porous medium of the stratum，the migration and adsorption of particles，and the aggregation of secondary and tertiary precipitates during each acidification with the scale at the same location，the blockage gradually transited from a dotted composite scale composed of inorganic and organic matter to block and strip，moreover，the larger the proportion of heavy components in crude oil was，the more severe the scaling was，and the larger the size of the scale body and the scaling area were. The easily soluble scale due to acidification was mainly carbonate scale，which was concentrated in the pore throat channels，and its morphological distribution was layered，dotted and streamlined. Insoluble scale was a complex scale mixed with crude oil and inorganic substances，which was concentrated at the blind end，pore wall and inlet end. It was difficult for ethanol to dissolve it at the reservoir temperature；and petroleum ether，which was prone to dissolve heavy components，was difficult to enter the chip，increasing the difficulty of unblockage. Under the same simulated crude oil composition and the process of non-backflow of residual acid，the more times of acidification，the worse the unblocking effect. The unblocking area at the injection end was larger than that at the extraction end. The unblocking effect of the main flow channel was significantly better than that of the branch channel，and some dissolved and reduced microscopic particles migrated backward. When the well was re-trapped and water was driven to form scale，affected by the cumulative effect of in-situ scale formation，the closer to the inlet end，the more secondary blockages were generated，and at the same time，large holes transformed into medium and small holes. The comparison of different processes showed that the effect of residual acid reflux was much better than that of direct water injection after acidification.

• Dual Network Self-healing Hydrogel Based on CMC@Fe₃O₄

  2025(4):631-639, DOI: 10.19346/j.cnki.1000-4092.2025.04.008

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  Conventional oilfield plugging agent in the deep water plugging of oil wells is prone to degradation and failure，the plugging agent is very easy to be damaged to lose the plugging effect after the absorption of liquid，it is difficult to meet the needs of deep water plugging. Based on the physical crosslinking network of CMC@Fe₃O₄，the physicochemical dual network self-healing hydrogel P（AM/AMPS/NVP）/CMC@Fe₃O₄ was constructed by using acrylamide（AM），2-acrylamido-2-methylpropanesulfonic acid（AMPS） and N-vinylpyrrolidone（NVP） as copolymerization monomers，potassium persulphate （KSP） as the initiator， hydroquinone（HQ）and hexamethylenetetramine（HMTA）as the crosslinking agent. The performance of gel strength，self-healing performance and temperature and salt resistance of the gel system were characterized. The optimum formulation of the self-healing gel system was as follows，91.6% CMC@Fe₃O₄ dispersion，5.6% AM，2.4% AMPS，0.4% NVP，pH= 9，the initiator KSP dosage was 0.8% by mass of the monomer，and the cross-linkers were 0.6% HQ and 0.6% HMTA. The gel strength of the gel was 230.6 Pa. The dehydration rate was only 6.21% after aging for 30 d at a high temperature of 130 ℃ and a high salinity of 2.2×10⁵ mg/L， exhibiting good temperature and salt resistance. The plugging rate of the gel system to the sand-filled pipe with water phase permeability of about 388 μm² was above 99%，and the breakthrough pressure was above 2.12 MPa，which could meet the needs of oilfield plugging. The self-healing of the gel could be achieved after aged at the temperature of 130 ℃ for 1 h，with a gel fracture elongation of 275% and a repair efficiency of 100%. the dual-network self-healing hydrogel demonstrates excellent performance in terms of gel strength，resistance to temperature and salt，sealing effectiveness and self-healing properties，and meets the requirements for deep plugging in oilfields.

• Plug Remover for Polymer Gel Based on Phase Transfer Catalytic Degradation

  2025(4):640-648, DOI: 10.19346/j.cnki.1000-4092.2025.04.009

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  In order to rapidly degrade and disperse three-dimensional network cross-linked polymer gel causing formation blockage， a non-redox targeted plug remover for polymer gel was developed with polarizing agent（polyether amine 1000），catalyst（vanadium （IV）oxy acetylacetonate），substitution agent（hydroxypropyl tetrahydropyrantriol，diethylenetriamine pentamethylphosphonate） and solubilizing dispersant（18-crown-6，trimethylsilyl ethanol）as the main components. The degradation and dispersion efficiency of polymer gel，core permeability recovery rate and corrosion resistance of the plugging remover were studied. The results indicated that the plug remover had a good degradation and dispersion effect on the polymer gel. At the temperature of 60 ℃，the 10% plug remover could make the degradation rate of the micro-nano gel particles with a particle size of 0.5—100 μm synthesized with acrylamide and acrylic acid as the main monomers more than 92%. The degradation rate of the polymer gel particles increased with the extension of time，reaching more than 90% after 72 h. The recovery rate of plug removal by core displacement was 87%，which could effectively remove the blockage caused by gel particles in the formation. At the temperature of 60 ℃，the corrosion rate of 10% plug remover on tubing and casing was 0.4898 g/（m² h），which was lower than that of conventional plug remover system in oilfield，and could ensure the safe construction on site. The field test results showed that the plug remover had a higher success rate of more than 90%，an average daily injection increase of 16.3 m³ per well，a decrease of 3.2 MPa in injection pressure，an effective period of more than 200 d，and a cumulative injection increase of more than 3920 m³ . The increasing injection effect of the plug remover was good，which was suitable for the application of under-injection wells caused by polymer gel particle profile control and flooding.

• Laboratory Experiment of Enhanced Oil Recovery by Multiple Gas Flooding in Low Permeability Reservoir

  2025(4):649-655, DOI: 10.19346/j.cnki.1000-4092.2025.04.010

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  CO₂ flooding is one of the effective methods to enhanche the oil recovery of low permeability and ultra-low permeability reservoirs. However，due to the lack of CO₂ gas source in some oil fields，its scale application is limited. For oil fields with abundant （ associated ） flue gas resources，it can be considered to use“flue gas + a small amount of CO₂”to form a multi-component gas for oil displacement. In this paper，the feasibility and adaptability of EOR by multiple gas flooding were explored by carrying out high pressure physical property analysis of multiple gas-formation oil and a series of core displacement experiments of enhanced oil recovery by multiple gas flooding. The results showed that the addition of a certain proportion of CO₂ to the flue gas would significantly improve the solubility of the gas and the ability to swell and decrease the viscosity of crude oil. The optimal multi-component gas composed of 48.9 mol% N2+49 mol% CO₂+2.1 mol% CH₄ was determined by combining oil recovery with oil change rate. The multi-component gas had better adaptability in both low permeability and ultra-low permeability cores. Compared with pure N₂ flooding and pure flue gas flooding，multi-component gas flooding could enhanced oil recovery by 4 percentage points—5 percentage points. The use of multi-component gas flooding can not only further enhance oil recovery，but also realize the rational and efficient utilization of flue gas，associated gas and other resources，which has important practical meaning.

• Research and Performance Evaluation of Nano Composite Supercritical CO₂ Foam Flooding System

  2025(4):656-663, DOI: 10.19346/j.cnki.1000-4092.2025.04.011

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  Aiming at the problems of gas channeling and low sweep efficiency of CO₂ flooding in micro-fractured reservoirs，the effects of anionic，zwitterionic and non-ionic CO₂ foaming agents and water-soluble and gas-soluble nanoparticle foam stabilizers on foam performance were evaluated by laboratory experiments. The nano-composite supercritical CO₂ foam system was optimized as 0.3% foaming agent CAB-35 + 0.5% water-soluble nanoparticle foam stabilizer As30 GA，and the foam performance of the nano-composite supercritical CO₂ foam system under reservoir conditions was studied. At the same time，the core flooding experiment of the nano-composite supercritical CO₂ foam system was carried out in the reservoir environment. The results showed that the foaming volume of the nano-composite supercritical CO₂ foam system was 550 mL，the half-life was 47 min，indicating good foaming and foam stability performance. The viscoelastic modulus of nano-composite supercritical CO₂ foam system was about 90 mN/m higher than that of ordinary foam（0.3% CAB-35）. The foam strength and stability were greatly improved by the synergistic effect of foaming agent and nano-particles. The nano-composite supercritical CO₂ foam system had good temperature resistance and pressure resistance. Under the reservoir conditions（salinity of 10×10¹ mg/L，80 ℃，42 MPa），the foaming volume reached up to 275 mL，and the half-life was 72 min. The plugging and oil displacement performance of nanocomposite supercritical CO₂ foam system in porous media was studied by physical model. In the gas-liquid ratio of 0.5—2.0，the maximum plugging pressure difference of core displacement was 1.6 MPa，the resistance factor was greater than 50，and the recovery degree was 28.8 percentage points higher than that of ordinary foam. The nano-composite supercritical CO₂ foam system had good stability，high sweep efficiency，excellent ability to improve oil recovery，and broad application prospects.

• Effect of Reservoir Heterogeneity on Continuous CO₂ Injection and Huff-n-puff Oil Displacement Characteristics

  2025(4):664-669, DOI: 10.19346/j.cnki.1000-4092.2025.04.012

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  Due to good injectivity and high oil-flooding capacity，CO₂ flooding has become a very potential method to enhance oil recovery in low permeability/tight oil reservoir，but due to the reservoir heterogeneity and fractures，gas channeling easily happens during the injection，which affect the development of reservoirs. The CO₂ continuous injection and huff-n-puff experiments were designed and conducted in cores with different permeability contrast，and oil recovery and oil distribution（scanned by CT）was measured as the index to investigate the effect of heterogeneity on CO₂ flooding. The results showed that，during the continuous injection of CO₂，When the permeability of the low-permeability layer was 5.0×10^-3 μm² ，as the permeability contrast increased from 1.0 to 2.2，the oil recovery was significantly reduced from 88.5% to 58.3%；when the permeability contrast further increased from 2.2 to 154.0，the decreasing trend of oil recovery slowed down from 58.3% to 44.8%. The injected CO₂ mainly flowed and displaced the crude oil in the high permeability layer，while the crude oil in the low permeability layer was basically unused，which was the reason why the recovery rate decreases significantly with the increase of heterogeneity. Even if the core heterogeneity was weak，the permeability contrast being of 2.2，which would lead to a significant reduction in oil recover of CO₂ flooding. When the permeability contrast was less than 2.2，the increase of heterogeneity leaded to a more significant decrease in oil recovery. When the permeability contrast was higher than 2.2，the recovery rate continued to decrease with the increase of permeability contrast，but the trend would slow down. After continuous injection of CO₂，the Huff-n-puff was conducted. The oil recovery of heterogeneous core models with permeability contrast of 1.0，2.2，15.5 and 154.0 increased from 58.3%，57.2%，44.8% to 80.4%，75.8%，74.4%， respectively. The oil saturation of low permeability layer decreased significantly，and the crude oil of low permeability layer was effectively utilized. CO₂ huff-n-puff is less affected by reservoir heterogeneity，which is a potential replacement method after continuous injection of CO₂.

• Preparation of Modified Nano-SiO₂ Particles and Their Imbibition Oil Displacement Effect in Tight Oil Reservoir

  2025(4):670-678, DOI: 10.19346/j.cnki.1000-4092.2025.04.013

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  To address challenges such as uneven permeability，poor crude oil mobility，and high extraction difficulty in tight reservoirs，three kinds of modified nano-SiO₂ particles with amphiphilicity，hydrophobicity and hydrophilicity were prepared by silane coupling agent homogeneous modification method and Pickering emulsion method to modify ordinary nanoparticles with particle size of 20—40 nm，which could adapt to small pores in tight oil reservoirs. Through the analysis of stability，interfacial activity and wettability，the amphiphilic Janus nano-SiO₂ particles were selected，and the subsequent imbibition displacement experiment was carried out. The results showed that the absolute value of Zeta potential of amphiphilic Janus SiO₂ nanoparticles could reach up to 31.01 mV. The transmittance of the dispersion reached 93.3% after standing for 3 days，and the transmittance of the dispersion had the smallest change. Amphiphilic Janus SiO₂ nanoparticles could reduce the oil-water interfacial tension to 0.37 mN / m. The amphiphilic Janus nano-SiO₂ particles could change the wettability of the core，reduce the capillary force in the reservoir pores，increase the fluidity of the oil phase，and achieve the effect of reducing pressure and increasing injection，so as to improve the oil displacement efficiency. The results of core simulation imbibition oil displacement experiment showed that the imbibition recovery rate（19.48%）of amphiphilic Janus nano-SiO₂ particle dispersion with a mass fraction of 0.01% was 12.23 percentage points higher than that of simulated formation water（7.25%），and 8.6 percentage points higher than that of ordinary nano-SiO₂ particle dispersion. With the increase of hydrophilic Janus nano-SiO₂ particle concentration，the imbibition recovery rate increased，and the recovery rate could reach up to 25.71% at a mass fraction of 0.05%. It is feasible to apply Janus amphiphilic nano-SiO₂ particles to enhance oil recovery in tight reservoirs.

• Temperature- and Salt-Tolerant Quantum Dot-based Oil Displacing Agents for Low Permeability Oil Reservoirs

  2025(4):679-684, DOI: 10.19346/j.cnki.1000-4092.2025.04.014

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  In response to the problem of the development of micro-nano pore throats in low-permeability reservoirs，the difficulty in the stripping and activation of crude oil，and the difficulty in utilization，the carbon-silicon quantum dot oil displacement agent was synthesized by solvent evaporation and thermal decomposition method. The structure of the synthesized carbon-silicon quantum dots was characterized by transmission electron microscopy（TEM），Fourier transform infrared spectroscopy（FT-IR ）and X-ray diffraction（XRD）. The temperature resistance，salt tolerance，interfacial activity，wettability and oil displacement performance of the carbon-silicon quantum dot oil displacement agent were investigated. The results showed that the quantum dots were spherical with a particle size of about 4 nm and good dispersion. XRD identified the（002）crystal plane of carbon and the（111）crystal plane of silicon of carbon-silicon quantum dots，which were in an amorphous state. FT-IR indicated that the surface of the quantum dots contained hydroxyl，carboxyl and amino groups，which could form hydrogen bonds with water molecules，improving the stability of the fluid. Under the condition of temperature of 135 ℃ and salinity of 300 g/L，the fluorescence spectrum of the quantum dots did not change significantly，exhibiting good temperature and salt tolerance. When the mass fraction of the quantum dots was 0.3%， the carbon-silicon quantum dots could reduce the oil-water interfacial tension to 0.92 mN / m，and could change the wettability of the rock surface to water-wet. The imbibition efficiency of the quantum dot oil displacement agent was 47.4%，being twice as big as that of the simulated formation water. NMR T2 spectra identified that the quantum dots could reach the micro-pores（1—10 ms）. On the basis of water flooding，oil recovery rate being of 63.95%，the injection of 0.5 PV carbon-silicon quantum dot oil displacement agent with mass fraction of 0.3% could enhance the recovery rate by 22 percentage points. The developed carbon-silicon quantum dot oil displacement agent is significant in enhancing oil recovery in low permeability reservoirs，which provides a good reference for efficient development of oil fields.

• Synthesis and Performance Evaluation of Gemini Maleic Anhydride Octylphenol Polyethylene Ethyl Ether Diesters

  2025(4):685-692, DOI: 10.19346/j.cnki.1000-4092.2025.04.015

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  Gemini surfactant is known as "a new generation of surfactants" and has great commercial value. In this paper，Gemini type octylphenol polyoxyethylene ether surfactant was synthesized by one step reaction using maleic anhydride and octylphenol polyoxyethylene ether as the main raw materials. The effects of reaction time，temperature，molar ratio of maleic anhydride to octylphenol polyoxyethylene ether，and catalyst dosage on the esterification rate of the product were investigated to optimize the reaction conditions. Furthermore，the surface tension，interfacial tension，wettability，emulsification，and viscosity reduction performance of the synthesized series of Gemini surfactants were evaluated. The optimal reaction conditions were determined as follows：the molar ratio of octylphenol polyoxyethylene ether to maleic anhydride was 2∶1，the reaction temperature was 200 ℃，the catalyst dosage was 4%，and the reaction time was 6 h. Compared with the conventional surfactant OP-10，the Gemini-type surfactant exhibited a lower critical micelle concentration（c_cmc）and superior oil-washing and viscosity-reduction performance. The gemini-type octylphenol polyoxyethylene ether surfactant（MOP-10）showed a c_cmc value of 0.052 mmol/L，and the interfacial tension between 1% MOP-10 solution and heavy oil reached 8.04×10^-2 mN/m，both one order of magnitude lower than those of OP-10. With the increase of the number of ethoxy groups in the Gemini-type octylphenol polyoxyethylene ether structure，the c_cmc value gradually decreased，while surface tension and interfacial tension increased，leading to a reduction in oil-washing and viscosity-reduction efficiency. This synthetic route is simple，the source of raw materials is wide，and the price is low. It can be used as an intermediate product to synthesize a variety of surfactants or polymers，and provide new raw materials for the development of surfactants and the modification of polymers.

• Effect of Ca²⁺ on Ultra-low Interfacial Tension of Petroleum Sulfonate Solution

  2025(4):693-699, DOI: 10.19346/j.cnki.1000-4092.2025.04.016

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  Abstract:

  In the binary composite flooding technology，the experiment study on the micro-mechanism of the influence of Ca²⁺ on ultra-low interfacial tension can provide reference for surfactant formulation optimization. By measuring the interfacial characteristic parameters of petroleum sulfonate KPS，such as the solubility product constant K_sp，surface tension，interfacial tension，and partition coefficient，the main conditions for KPS to form ultra-low interfacial tension were clarified. The results showed that the influence of Ca²⁺ on the surface tension of the KPS solution was related to the decrease in the polarity of the micellar microenvironment. For the KPS system prepared with de-calcium water，the interfacial tension（IFT）was two-order-of-magnitude higher than that of calcium-containing solutions，with IFT restoration observed upon reintroducing 40 mg/L Ca²⁺ . Partition coefficient analysis in 0.3% KPS/kerosene systems demonstrateed that 40 mg/L Ca²⁺ induced optimal surfactant distribution（K= 0.101）with molecular minimum occupied area（A_min）of 0.58 nm². At this time，the sum of the concentrations of KPS in the two phases was less than the total concentration，and the“excess”KPS molecules were concentrated in the interfacial layer. A novel "interfacial complexation" model was proposed，suggesting that Ca²⁺ bridged two sulfonate groups（—SO₃²）near the oil-water interface，which was further validated through disodium phthalate solution experiments. The“interfacial complexation”model can provide molecular-level insights for understanding the microscopic mechanism of calcium ions affecting the interfacial tension of the oil displacement system.

• Water Lock Remover Based on Hydrophobic Modified Pseudomonas Metabolites

  2025(4):700-706, DOI: 10.19346/j.cnki.1000-4092.2025.04.017

  Abstract: (0) HTML (0) PDF (0.00 ByteKB)(0)

  Abstract:

  In view of the problem that the production of tight gas wells decreases due to water lock，and the development effect deteriorates，a water lock remover based on metabolites of hydrophobic modified Pseudomonas was prepared，and the surface/interface properties，wettability and spontaneous imbibition ability of the water lock remover were tested，and the effect of water lock removal was evaluated through the core displacement experiment. The results showed that the water lock remover could form a dense superhydrophobic biofilm in the gas reservoir，improve the relative permeability of the gas phase and reduce the relative permeability of the water phase. The 0.6% water lock remover could form a stable adsorption on the surface of the reservoir rock and restore the reservoir permeability of 56%—80%. After chemical treatment，the spontaneous liquid uptake and maximum liquid uptake rate of the treated core（about 60 g）decreased from 0.36 g and 0.05 g/min to 0.16 g and 0.01 g/min，respectively. The simulation experiment of core displacement showed that the water lock remover could effectively reduce the relative permeability of water phase and increase the relative permeability of gas phase，which was mainly reflected in the increase of the water-phase relative permeability shape factor and the decrease of its endpoint value，as well as the decrease of the gas-phase relative permeability shape factor and the increase of its endpoint value. The water lock remover had good adaptability to the water lock damage of the four gas field reservoirs，which could effectively remove the water lock and restore the reservoir permeability.

• Correction Method of Polymer Concentration and Viscosity Relationships in Numerical Simulation of Polymer Flooding

  2025(4):707-714, DOI: 10.19346/j.cnki.1000-4092.2025.04.018

  Abstract: (0) HTML (0) PDF (0.00 ByteKB)(0)

  Abstract:

  Due to the influence of reservoir porous media shear and other factors，the viscosity-concentration relationship of polymer solution obtained by experimental methods is difficult to directly be applied in numerical simulations. At present，the commonly used empirical or analogical methods have large errors，and there is still a lack of effective numerical simulation methods for determining the viscosity-concentration relationship in polymer flooding. In this paper，the experiment of the influence law of polymer flooding was designed and carried out，and the numerical simulation model of polymer flooding core was established to fit the experimental results. The viscosity-concentration relationship of polymer flooding numerical simulation under different temperature，salinity and permeability conditions was determined. The prediction model of polymer viscosity-concentration relationship adjustment was established，and then the method of determining the viscosity-concentration relationship of polymer flooding numerical simulation was formed. Research results was shown that using the proposed method to determine polymer viscosity concentration relationship data，the fitting error of polymer flooding water content was 1.81%，which was 7.42% lower than that of the existing empirical. The accuracy of polymer flooding numerical simulation was improved，which provided reliable parameters and references for numerical simulation of polymer flooding.

• Study on the Anti Swelling and Shrinkage Swelling Mechanism of DSJ-1

  ZHAO Kaiqiang

  Abstract: (338) HTML (0) PDF (0.00 ByteKB) (518)

  Abstract:

  For reservoirs with high shale content and low permeability, many reports have pointed out that shrinkage swelling agents can reduce pressure and increase injection, but there is no research report on the relevant mechanism. In this paper, the effect of DSJ-1 shrinkage swelling agent addition on anti swelling ratio and shrinkage swelling ratio was investigated, and the bentonite before and after treatment were characterized by XRD, XRF, zeta potential, thermogravimetry, particle size distribution and optical microscope. Through characterization, the anti swelling and shrinkage swelling mechanisms were analyzed. It was found that DSJ-1 was mainly adsorbed on the clay surface during the anti swelling treatment, and the adsorption amount and zeta potential had the greatest impact on the anti swelling rate. During the shrinkage swelling treatment, DSJ-1 was mainly adsorbed between crystal layers, and the particle aggregate size and zeta potential affected the shrinkage swelling rate.

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• Molecular design, performance and mechanism study of electrostatic effect enhanced film-forming sand control agent

  SONG Jinbo

  Abstract: (368) HTML (0) PDF (0.00 ByteKB) (487)

  Abstract:

  Aiming at the problems of complex injection procedure, high cost, great damage to formation permeability of traditional chemical sand consolidation agents, and weak adsorption capacity and short validity of polymer sand control agents, the existing polyamide polymer sand control agents were designed and modified by molecular simulation and experiment. The synthesis, structure characterization, performance test and formula optimization of quaternary ammonium modified and strengthened polyamide sand control agents were completed, and the mechanism of sand control agent with enhanced film formation was determined.

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• Thinking on shale gas fracturing flowback fluid treatment technology under carbon neutral vision

  DONG Yuan-wu, TANG Shan-fa

  Abstract: (427) HTML (0) PDF (0.00 ByteKB) (623)

  Abstract:

  With the development of carbon neutralization goals in China, petroleum is facing a lot of pressure to reduce carbon emission. This study shale gas fracturing fluid flowback low carbon as the goal, shale gas fracturing fluid flowback were analyzed characteristics and potential impact on water quality, and probes into the existing processing technology and principle are reviewed, and points out that the shale gas fracturing fluid flowback process should reduce the pollutant emissions, energy recovery and utilization, saving energy and reducing consumption three aspects, It is suggested that the application of less or no water fracturing technology, clean fracturing fluid technology, new microbial treatment technology, energy saving treatment technology of fracturing flowback fluid, new energy replacement technology and energy saving technology of intelligent equipment in the development of oil and gas fields should be vigorously developed and promoted to ensure the reasonable development and sustainable development of shale gas.

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• Synthesis and performance evaluation of guar gum modified with glycidyl surfactant in seawater-based fracturing fluids

  Zhang Yongtao, Qiu Shoumei

  Abstract: (334) HTML (0) PDF (0.00 ByteKB) (604)

  Abstract:

  In response to the problem that a large number of metal ions in seawater adhere to the surface of guanidine gum, which inhibits the swelling of guanidine gum molecular chains and cannot meet the continuous mixing in the field, epichlorohydrin and octadecenoic acid amidopropyl dimethyl as raw materials were synthesized and cationic monomer GOA was obtained, and then GOA was grafted onto guanidine gum molecular chains to obtain seawater-based fracturing fluid thickener epoxy propyl surfactant modified guanidine gum. Coulombic forces and electrostatic repulsion on the molecular chains of the modified guanidine gum prevented metal ions from attaching to the molecular chains of the guanidine gum, ensuring the swelling of the guanidine gum molecules and improving the salt resistance of the guanidine gum. The dissolution, salt resistance, temperature and shear resistance, sand-carrying and glue-breaking properties of GOA modified guanidine adhesive were investigated in the paper. The results show that the dissolution rate of GOA-modified guanidine gum in seawater is significantly higher than that of ordinary guanidine gum, and the median particle size in seawater is about 1/5 of that of ordinary guanidine gum molecules; the viscosity of GOA modified guanidine gum can reach 80% of the final viscosity after 5 min of swelling at 500 r/min; microscopic analysis shows that GOA-modified guanidine gum forms a clearly visible irregular mesh nematic structure, and the guanidine gum molecular chain The microscopic analysis showed that the GOA modified guanidine gum formed a clearly visible irregular net-like nematic structure, and the molecular chains of guanidine gum were fully expanded and the cross-linked bonds increased. The viscosity was still higher than 50mPa·s after continuous shearing at 160℃ and 170s-1 for 120min, indicating that the GOA modified guanidine glue fracturing fluid has good salt, temperature and shear resistance and the viscosity of the broken fluid is 1.6mPa·s. The residue content in the broken fluid is 297mg/L, which meets the requirements of field fracturing construction.

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• Detection Method of Olefin Sulfonate Used in Oil and Gas Field by Liquid Chromatography-Mass Spectrometry

  Zhang Xiaobin

  Abstract: (727) HTML (0) PDF (0.00 ByteKB) (708)

  Abstract:

  Aiming at the disadvantages of traditional titration detection methods such as low sensitivity, poor anti-interference ability, and long detection period, this paper uses liquid chromatography tandem quadrupole mass spectrometer to establish a detection method for α-olefin sulfonates used in oil and gas fields, and realizes the detection of target concentration in olefin sulfonate products, injection fluid and produced fluid. The detection conditions are as follows: the chromatographic column is an anionic column; the mobile phase is 55% methanol + 45% 8 mmol/L ammonium acetate aqueous solution (volume ratio), isocratic Elution; mass spectrometry detection conditions are electrospray ion source, negative mode, full scan. The recovery rates of this method for olefin sulfonate products, injection fluid, and produced fluid were 82.63-96.37%, 78.60-95.41%, 82.68-95.72%, respectively. One sample detection was completed in 8 minutes, and the lower limit of quantification was 5 ppm. And polymer, trace oil, etc. have no effect on the detection result, that is, the method is fast, sensitive, and has strong anti-interference ability.

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• Study on a Noval Solid-free Polymer Gel System for Grouting in Luohe Formation Sandstone

  LI Jiaming, ZHAO Guang, DAI Caili

  Abstract: (645) HTML (0) PDF (0.00 ByteKB) (1113)

  Abstract:

  The frequent water gushing in sandstone mining strata of Luohe Formation has seriously affected the safety production of the mine. The traditional grouting systems are faced with the problems of serious percolation effect and uncontrollable gelation performance, which is difficult to achieve effective regulation of fissure water. In this work, the microscopic characteristics of sandstone pores are clarified by analyzing the mineral composition and microscopic morphology of typical core samples. A solid-free polymer gel system with low cost and excellent stability is constructed for grouting, and the grouting performance evaluation is further carried out. The results show that the small pore diameter and poor connectivity are the geological reasons for the difficulty of smooth injection and long-distance migration of the traditional grouting systems. The noval polymer gel system with low cost, solid-free and easy injection for grouting can achieve gelation within 48h and has excellent long-term aging stability. The system has good injectivity and the pressure attenuation is not obvious after continuous flooding, with the plugging ratio remaining above 80 %. The system increases the seepage resistance and blocks the subsequent fluid by occupying the large channel or fracture space, which realizes the effective plugging of the water layer. The results of this work provide new ideas for the grouting and water plugging in Luohe Formation sandstone.

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• Construction and performance of high stability supercritical CO2 Foam for channeling blocking during CO2 flooding

  LI Weitao

  Abstract: (947) HTML (0) PDF (0.00 ByteKB) (1136)

  Abstract:

  Aiming at the problems of low sweep efficiency of CO2 flooding and poor performance of conventional foam profile control ability, a high stability supercritical CO2 foam system composed of amphoteric surfactant HSD and modified SiO2 nanoparticles is constructed. Low permeability reservoirs in Shengli Oilfield are buried deep and have high temperature.The system showed good high-temperature resistance. At 120 ℃, the concentration of 0.5% nanoparticles increased the half-life of foam from 17 minutes to 40 minutes, and the stability was improved by nearly 2.5 times. The increase of reservoir pressure can increase both bubble volume and foam stability. Based on the power law model, the effect of nanoparticles on the rheological properties of supercritical CO2 foam system was studied. The results showed that the apparent viscosity of the system increased with the increase of the concentration of nanoparticles under the same shear rate, and the consistency coefficient increased from 0.073 to 1.22. The change rule of apparent viscosity of supercritical CO2 foam in porous media is simulated through core displacement experiment. The steady-state apparent viscosity of foam in porous media increases with the increase of nanoparticles. The foam of supercritical CO2 foam is stacked and discharged in "granular" shape. The size of foam is about 10 ~ 20um. Finally, the mechanism of nano particles enhancing the stability of CO2 foam was confirmed through experiments. The hydrophilic nano silica had interfacial activity due to the adsorption of surfactant molecules, which was adsorbed from aqueous solution to the gas-liquid interface, thus improving the stability of foam.

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• Recent progress in synthesis of oligomeric cationic surfactants

  QIAO Fulin

  Abstract: (947) HTML (0) PDF (0.00 ByteKB) (1145)

  Abstract:

  In recent years, oligomeric surfactants, as a novel class of surfactant with superior efficiency at very low concentration, have shown promising applications in the fields of enhance oil recovery, pharmaceuticals, corrosion inhibitors, and so on. Oligomeric surfactants are composed of two or more amphiphilic moieties, which are chemically linked by a spacer group, and they bridge the gap between monomeric surfactants and polymeric surfactants. With the help of the spacer group, the spatial distance of multiple amphiphilic moieties becomes closer, contributing to the stronger aggregation ability of the oligomeric surfactants. Meanwhile, the structures of the spacer group and the topological configuration are more diversified, resulting in multifarious transition processes of molecular configuration and aggregation morphology. These characteristics make them show unique advantages as highly-efficient oilfield chemicals and stimuli-responsive soft materials, but the difficult synthesis processes have been identified as the bottleneck of their systematic investigations. In this review, the synthesis methods of linear, star-like and ring-type oligomeric cationic surfactants, which are classified by the spatial topological structure, are summarized in detail, and a brief review of future perspectives on the oligomeric surfactants are also discussed.

  • 1
• Research status and prospect of lost circulation formation drilling fluid plugging materials

  LIU Jing, MA Cheng

  Abstract: (891) HTML (0) PDF (0.00 ByteKB) (1335)

  Abstract:

  Lost circulation is the main technical problem that restricts the improvement of the quality and efficiency of oil and gas drilling engineering. Improving the success rate of one-time plugging is an urgent need to ensure "safe, efficient and economic" drilling in global oilfields. Aiming at the study of drilling fluid leakage mechanism, the drilling fluid leakage mechanism is systematically summarized. Through the research of domestic and foreign scholars in recent years, plugging materials such as bridging, high water loss and curable have been developed. The properties and interaction mechanism of various plugging materials such as bridging, high water loss, curing, polymer gel, etc. are systematically introduced. The existing problems of plugging materials are clarified, and the future development direction of plugging materials is proposed.

  • 1
• Low interfacial tension small molecule oil displacement agent to improve oil recovery in low permeability reservoir

  MENG Wenyu, TANG Shanfa

  Abstract: (726) HTML (0) PDF (0.00 ByteKB) (1300)

  Abstract:

  Poor injection of low permeability reservoirs, low efficiency of wash oil, water flooding can effectively improve recovery factor and so on question, this paper proposes a low interfacial tension of small molecular oil displacement agent (LST) new technology improve the recovery factor of low permeability reservoir, the interfacial activities of evaluation of the oil displacement agent, viscosity, emulsification, wettability and its reservoir environment adaptability and oil displacement effect. The results show that the oil displacement agent has good interfacial activity and viscosity. When the mass fraction is 0.4%, the oil-water interfacial tension is as low as 0.012mN/m-1, and the viscosity is close to that of the reservoir oil (3.4mPa?s). The oil displacement agent also has good oil-water emulsification ability, little influence of static adsorption on interfacial activity and viscosity enhancement, and good hydrophilic wettability, which can effectively improve water recovery efficiency at low dose or cost. By injecting 0.4%LST(0.4PV), the water flooding recovery of homogeneous core (50mD) can be increased by 11.210%, and the comprehensive water

  • 1
• Performance Evaluation of Gel Plugging System for High Pressure Water Injection Well

  WANG Wanfei, FU Hong

  Abstract: (729) HTML (0) PDF (0.00 ByteKB) (1343)

  Abstract:

  In order to meet the strength, gelation time and gel breaking performance requirements of gel plugging system for high pressure water injection wells under pressure, a temperature-resistant and salt-resistant gel plugging system was prepared by using AM / AMPS ( acrylamide / 2-acrylamide-2-methylpropanesulfonic acid ) as binary polymer system and Smel30 (Trihy-droxymethyl compound) as crosslinking agent. The effects of temperature, inorganic salt, simulated oil content and shear time on gelation time and gel strength of the gel system were studied. At the same time, the effect of dosage of gel breaker sodium persulfate on gel breaking effect of gel system was studied. The results showed that the gelation time was shortened with the increase of temperature. When the temperature was 60 °C, the gelation strength was 73.5Pa and the gelation time was 7 h. The addition of inorganic salts reduced the distance between polymer chains, shortened the gelation time, and slightly increased the gel strength. The influence of three salts on gelation time and gel strength was NaCl < MgCl2 < CaCl2; the system has strong resistance to oil pollution; after shearing for 60 min, the gel strength can still maintain more than 81 %, which has strong shear resistance. The gel system did not dehydrate after 15 days of aging and still had strong gel strength; sodium persulfate can be used as a gel breaker with high efficiency and low cost, and the apparent viscosity of the residue is less than 64.4 mPa·s.

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• Study of Surface-active Injection Enhancement System for Reservoirs with Low Permeability and High Salinity

  ZHANG Guoqing, GONG Zhuoting, YI Xiao, WANG Zhengliang, ZHENG Yancheng

  Abstract: (709) HTML (0) PDF (0.00 ByteKB) (1162)

  Abstract:

  Low permeability reservoirs have the characteristics of small pore throat radius, low permeability and water absorption ability. In order to improve the recovery efficiency of chemical flooding, a compounded system of alcohol ether sulfonate and betaine surfactant was established. The alcohol ether sulfonate DP6E6S characterized by 1H NMR was obtained by the introduction of propylene oxide and ethylene oxide into dodecanol and sulfonation. It was compounded with cetamide betaine PNC to evaluate surface properties, interaction properties, interface properties, wettability and emulsification properties of the complex system and the injection enhancement was obtained by core flooding experiments. It is showed that PNC and DP6E6S have strong synergistic effect of reducing critical micelle concentration (cmc) and surface tension effectively. The interfacial tension of the compound system decreases with the increase of salinity, especially n(PNC): n(DP6E6S) =2:3 and 1:1 which can reach 10-3 mN?m-1 in a wide range of salinity (>5%). The mole ratio of n(PNC): n(DP6E6S) =2:3 and 1:1 formed the more volume phase emulsion showed the best dissolution effect. The particle size of emulsion droplets first decreases and then increases with the increase of salinity. The interfacial tension of the compounded system is still low after core adsorption showed good adsorption resistance. The mole ratio of n(PNC): n(DP6E6S) =1:1 with larger wetting angle and smaller capillary force is conducive to depressurization and injection enhancement. The depressurization rate of the two optimized systems can reach 28.9% and 23.9%, respectively, indicating that low interfacial tension and high wetting angle are conducive to depressurization and injection enhancement of low permeability reservoirs.

  • 1
• Mechanical strength of polyacrylamide composite hydrogel reinforced by nanocrystalline cellulose

  MA Yanqi, LIN Meiqin

  Abstract: (906) HTML (0) PDF (0.00 ByteKB) (1384)

  Abstract:

  The strength of gels determines its use and high mechanical strength gels have been applied in many fields. In order to enhance the strength of acrylamide (AM) gels, nanocrystalline cellulose (NCC) was used to prepare the AM/NCC composite hydrogel.The effects of NCC on the tensile properties, compressive properties, adhesion properties and viscoelastic properties of AM/NCC composite hydrogels were investigated by using texture analyzer and rheometer, and the microstructure of the composite hydrogels was observed by scanning electron microscope (SEM).The results showed that the tensile strength, compressive stress, adhesion and viscoelasticity of AM/NCC composite hydrogel were significantly higher than those without NCC. When the mass ratio of AM to NCC was 5:3, the tensile strength, compressive stress and viscoelasticity of the composite hydrogel reached the maximum. The toughness of AM/NCC composite hydrogel was significantly enhanced, and the tensile stress and adhesion force were nearly 4 times higher than those of AM gel.The strength of AM/NCC composite hydrogel is related to its microstructure, and the network structure of AM/NCC composite hydrogel is significantly denser than that of AM gel.

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• Construction and Performance Evaluation of Emulsification-Stripping Dual Effect System for Heavy Oil

  HU Junjie, ZHANG Guicai

  Abstract: (854) HTML (0) PDF (0.00 ByteKB) (1147)

  Abstract:

  There are some problems in the development of the heavy oil reservoir in Shengli Oilfield, such as high viscosity and poor fluidity of crude oil, which the recovery efficiency of the water drive is not ideal. Therefore, the emulsification-stripping system was constructed with the instability coefficient of emulsification, the shrinkage rate of oil film and the minimum emulsifying speed as indexes. The emulsification and stripping ability of different surfactants for heavy oil were evaluated. The compound system of 0.3wt%CBT/ASC（m（CBT）：m（ASC）=3:2） was optimized. The displacement effect of the emulsification-stripping system was evaluated by the laboratory sand-filling flow experiment. The mechanism of its action was studied by a microcosmic model. The results showed that CBT had excellent emulsification performance and significantly reduced interfacial tension for heavy oil, and ASC had good stripping ability for heavy oil. The compound system has excellent emulsification-stripping function, and the enhanced oil recovery rate can reach 14.18%. The research results have important guiding significance for efficient development of heavy oil reservoir.

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• Screening and evaluation of cheap nutrient system for sandstone reservoir in well block LQ, Xinjiang

  WANG Hongbo, MA Ting

  Abstract: (521) HTML (0) PDF (0.00 ByteKB) (1295)

  Abstract:

  According to the nutritional requirements of the main oil recovery functional bacteria in the sandstone reservoir of LQ well block, the optimal carbon source, nitrogen source and phosphorus source were selected through single factor experiment, and the concentration of each component was preliminarily determined, on this basis, the significant influence factors of each component were analyzed by Plackett-Burman experiment and factor removal experiment, and the concentration of each component was determined, finally, response surface test was used to determine the concentration of each component, the final concentration was obtained by further optimizing each component according to the factors. The results showed that the selected nutrient system had good emulsifying effect, the main oil recovery function gene hydrocarbon oxidation gene reached 10_⁷copies/ml, and the physical model oil displacement experiment improves oil recovered by 11.65%. This study provides a good technical support for the field test of microbial flooding in well block LQ.

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• Research progress of drag reducers for fracturing and its drag reduction mechanism

  SI Xiaodong, LI Mingzhong

  Abstract: (1683) HTML (0) PDF (0.00 ByteKB) (1629)

  Abstract:

  Drag reducer is the key additive of fracturing fluid for unconventional reservoir reconstruction, such as tight sandstone and shale, and its performance will directly influence on the fracturing operation effect. The advantages,disadvantages and application of different drag reducers were analyzed. The turbulent drag reduction and drag reduction failure mechanism of drag reducers were emphatically described. The research progress of nanomaterials in fracturing drag reduction was summarized. This paper points out that in unconventional reservoir fracturing environment such as high temperature, high shear and complex medium, the new type of multi-functional composite drag reducers with the advantages of stability, high efficient drag reduction, low reservoir damage, strong sand carrying capacity, easy flowback and easy recycling will be an important research direction in future.

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• Effect of autogenous heat system on fracturing fluid gel breaking performance

  SHEN Xiulun

  Abstract: (982) HTML (0) PDF (0.00 ByteKB) (1843)

  Abstract:

  Aiming at the problems of incomplete fracturing and low flowback ability in low-temperature shallow oil and gas wells, the heat generation of three different autogenous heat generation systems, including nitrite and ammonium salt, chromium trioxide, glucose, and hydrogen peroxide, was investigated. And the impact on the fracture gel breaking performance. The experimental results show that the heat generation of the heat generating system of nitrite and ammonium salt is the highest, and the temperature can reach above 80℃. In addition, the order of addition of three different heat generating systems and breakers is also determined in the experiment to make fracturing The liquid gel breaking effect is the best. Among them, the order of adding the heat generating system of glucose and chromium trioxide and the heat generating system of nitrite and ammonium salt is to add the heat generating system first, then add the APS breaker and hydrogen peroxide heat generating system. The order of addition is to add both autogenous heat system and APS breaker at the same time; finally, it is concluded that the autogenous heat system of nitrite and ammonium salt is the best additive for fracturing fluid gel breaking system, which can reduce the viscosity of fracturing fluid to 6 Below mPa.s, the best glue breaking performance.

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• Development and application of double-protection weighting agent for drill-in fluidZhuo Lvyan You Zhiliang Zhao Cheng

  ZHUO Lvyan

  Abstract: (620) HTML (0) PDF (0.00 ByteKB) (1324)

  Abstract:

  The arsenic content of barite supplied in China mostly exceeds the filter value of Second type of construction land in‘GB 36600-2018 Soil environmental quality Risk control stardard of soil contamination of development land’. Iron ore powder and ilmenite powder are commonly used as weighting agents, but they wear drilling tools seriously, which affects the electrical measurement results, and the chroma of drilling fluid is not up to standard after use, so they are rarely used now. Calcium carbonate is also a common weighting agent, due to its low viscosity, the viscosity effect is obvious, which has an impact on drilling. In view of the shortcomings of the environmental protection performance and application performance of the weighting agent, choose calcium carbonate weighting agent,adding barite into it proportionally,after surface coating modification, dry activation treatment and other production processes, The viscosity effect and the arsenic content is reduced.At the same time, it is beneficial to the hydrocarbon reservoir protection characteristics of calcium carbonate weighting agents . Innovation has formed a double-protection weighting agent that protects oil and gas reservoirs and the environment.The technology has been applied to 10 wells,all wells were drilled safely. Compared with the average value of adjacent wells, the penetration rate increased by 10%, the average hole diameter expansion rate decreased by 1.8%, the average oil production per meter of single well increased by 0.60t, and the arsenic content of mud cake reached the standard screening value (less than 60mg/Kg).

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• Optimization of synthesis conditions and evaluation of indoor oil displacement effect of a supercritical carbon dioxide thickener

  Fu Hong

  Abstract: (851) HTML (0) PDF (0.00 ByteKB) (1079)

  Abstract:

  carbon dioxide flooding (CO2) is an effective means to further develop old oilfields with high water cuts and improve oil recovery based on tertiary oil recovery. Aiming at the gas channeling problem caused by the large viscosity difference between carbon dioxide and crude oil, a supercritical carbon dioxide thickener agent P-1 that can be applied to oil flooding was prepared. Through orthogonal experimental analysis, it is concluded that the amount of initiator has the greatest influence on the molecular weight distribution of the reaction, the optimal molar ratio of the synthetic monomer is 4:1:1, the molecular weight distribution is 1.12, and the yield is 88%. The synthesized product under optimal conditions was characterized by infrared characterization, and the characteristic absorption peaks matched the product. The evaluation results show that the saturation solubility of P-1 in supercritical carbon dioxide is 2.30%, and the minimum miscible pressure is 7.77Mpa.The thickener with a monomer concentration of 0.2% increased the viscosity of supercritical carbon dioxide by 42 times at 30Mpa, 50℃, the viscosity was 1.1675mPa.s, and the viscosity retention rate was 46.41%, while the temperature was raised to 110℃. Simulating the formation environment (15MPa), adding the thickening agent P-1 with a mass concentration of 0.2% can effectively improve the oil displacement effect of supercritical carbon dioxide flooding, and the lower the permeability, the more significant the extraction effect. In the same core, the total recovery degree of supercritical carbon dioxide flooding is more than 10% higher than that of supercritical carbon dioxide flooding after water flooding.

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• Experimental on lubricating oil for drilling fluid based on aging oil

  Jiaxue Li

  Abstract: (556) HTML (0) PDF (0.00 ByteKB) (1186)

  Abstract:

  Aging oil, a by-product of oil field surface production, has complex interface characteristics and is difficult to be dehydrated. Using aging oil to develop drilling fluid lubricant can make use of its emulsifying stability and avoid the problem of removing mud, sand and water from aging oil.Through a large number of experiments, the key emulsifier of drilling fluid lubricant based on aging oil is OP-4, the wetting agent is ABS, and the stabilizer is Na-CMC. The experiment determines that the best formula of the drilling fluid lubricant is 100ml drilling fluid + 3ml aging oil + 1.5g OP-4 + 0.15g ABS + 0.015gNa-CMC. Through the benchmarking national standard experiment, the developed drilling fluid lubricant based on aging oil meets the requirements for lubricants in the standard. Using aged oil as base oil to develop drilling fluid lubricant is a feasible resource treatment scheme for aged oil, which has great application value.

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• PREPARATION OF HIGHLY POROUS NI-MO CATALYST BASED ON γ-AL₂O₃ AND ITS CATALYTIC EFFECT ON ULTRA-HEAVY OIL VISCOSITY REDUCTION

  Yuan Chengdong

  Abstract: (543) HTML (0) PDF (0.00 ByteKB) (1070)

  Abstract:

  The ultra-heavy oil reservoir in Tahe Oilfield is currently producing by mixing light oils with ultra-heavy oils in wellbore to reduce viscosity. However, the high ratio of needed light oils and abnormal fluid production caused by uneven mixing make the production low efficient and high cost. To solve this challenge, in this work, we proposed the technology of catalytic ex-situ upgrading for viscosity reduction + reinjection of upgraded oil into wellbore to save the amount of injected light oils and improve the recovery efficiency. To develop a catalyst system that can effectively reduce the viscosity of the ultra-heavy oil and achieve high-level ex-situ upgrading, a Ni-Mo catalyst with high porosity based on γ-Al2O3 carrier was developed and its catalytic effect on the ex-situ upgrading and viscosity reduction was evaluated. The results show that the developed Ni-Mo catalyst can reduce the viscosity of ultra-heavy oil at 50 ℃ from 28200 mPa.s to 298 mPa.s. The viscosity is reduced by nearly 100 times, and the viscosity reduction rate is 98.94%. The density is decreased from 1.007 g/ml to 0.8724 g/ml. At the same time, the content of saturates is significantly increased, and the content of resins and asphaltenes was greatly decreased. The developed catalyst system shows an excellent ex-situ catalytic upgrading effect for extra-heavy oil and has a great potential for field application.

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• Evaluation of inhibition effect of ionic liquid on asphaltene precipitation in crude oil under high temperature and pressure

  CAO Pengfu

  Abstract: (655) HTML (0) PDF (0.00 ByteKB) (1061)

  Abstract:

  ionic liquids have great potential to prevent asphaltene precipitation in reservoir development, but the inhibition effect of ionic liquids under high temperature and high pressure is not clear. Based on the calibration of the relationship between asphaltene content and absorbance in organic solvents, the inhibitory effects of two ionic liquids [bmim] Cl and [bmim] BR and two common commercial inhibitors on asphaltene precipitation in crude oil were evaluated by spectrophotometry, and the determination experiments of asphaltene precipitation at high temperature and high pressure were carried out with the best inhibitor and ratio concentration, The effects of ionic liquid on the initial pressure of asphaltene precipitation (AOP) and the size of asphaltene aggregate in formation crude oil and CO2 injected formation crude oil were studied. The experimental results show that the inhibitory effect of ionic liquid [bmim] BR on asphaltene precipitation is much higher than ionic liquid [bmim] Cl and two other commercial inhibitors, and the optimal concentration is 600 ppm. The AOP of pure formation crude oil is 28.7mpa. When [bmim] BR is added, the AOP decreases by 21.6%. When isopropanol is added to ionic liquid, the AOP decreases by 29.6%. The AOP of formation crude oil saturated with 30mol% CO2 is 31.6mpa, which is 10.1% higher than that of pure formation crude oil. When isopropanol and ionic liquid mixed solvent are added, the AOP decreases by 44.3%. Isopropanol can produce ternary interaction with [bmim] BR and CO2, improve the activity of [bmim] BR, greatly reduce the AOP of saturated CO2 crude oil, slow down the growth rate of asphaltene particle size, reduce the deposition depth and blockage degree of asphaltene in the wellbore, and introduce asphaltene deposition into more controllable nodes, which has broad application prospects. The results obtained provide a reference for the prevention and control of asphaltene deposition and rational and efficient development.

  • 1
• Oil contaminated soil treatment new technology-the applicability of the plant type microbial fuel cell research

  gaojie

  Abstract: (555) HTML (0) PDF (0.00 ByteKB) (1114)

  Abstract:

  Oil enters the soil during refining, storage, transportation and use, causing pollution. Oil pollutants are highly harmful and difficult to deal with. Plant Microbial Fuel Cell (PMFC) is proposed to solve this problem. The PMFC was constructed with oil-contaminated soil as anode sludge. By detecting the output voltage, power density, apparent internal resistance and oil removal rate, the battery plants and electrode materials were optimized, and the optimized PMFC was used to explore the oil concentration applicability and optimum scope of application. The results showed that the green dill in plants could not survive in the anaerobic environment of PMFC, while the electricity production and degradation properties of white crane taro-PMFC were better than those of Lentinus edodes-PMFC; Compared with carbon sponge-PMFC, the power generation performance and degradation performance of carbon felt-PMFC in electrode materials are significantly improved; PMFC with white crane taro as battery plant and carbon felt as electrode material is suitable for any oil concentration, and with the increase of oil concentration, the power generation performance and degradation performance of PMFC show a trend of increasing first and then decreasing. So there is an optimal oil concentration range of 5-10g/kg. PMFC technology provides a new idea for oil-contaminated soil treatment, which can effectively deal with soil pollution problems while generating electricity and achieve a win-win situation.

  • 1
• Study on low temperature degradation of HPAM gel by activation of persulfate

  ZHU Jianjun, WANG Yefei

  Abstract: (569) HTML (0) PDF (0.00 ByteKB) (1133)

  Abstract:

  Temperature is a key factor limiting the degradation of polymer gel. Aiming at the blockage caused by polymer gel in low temperature reservoirs, the system of TA activated persulfate was proposed to use as a plugging remover to degrade polymer gel in this work. First, the quenching experiment and the radical test were used to determine the mechanism to degrade the polymer; the second was to study the effect of persulfate concentration, TA concentration, temperature and anions in formation water on the degradation, and the optimal reaction concentration was selected according to the change of polymer gel’s degradation efficiency and the corrosion with the concentration; Finally, the degradation effect of the system was compared with the conventional polymer plugging removers. The results showed that TA activated persulfate can rapidly degrade the polymer gel at 35 ℃, and the superoxide anion radicals are the main active radicals in degradation reaction. Compared with other polymer plugging removers, the said system of TA activated persulfate could rapidly degrade polymer gel with mild corrosion in the low temperature reservoir.

  • 1
• Study on improving anti-pollution performance of shale gas well cementing cement slurry with surfactant

  HE Guanxi

  Abstract: (635) HTML (0) PDF (0.00 ByteKB) (1264)

  Abstract:

  When shale gas reservoir is developed by horizontal wells, due to casing eccentricity and irregular well diameter, the displacement efficiency of oil-based drilling fluid is usually low. It is inevitable that some oil-based drilling fluid will be mixed into cementing cement slurry and pollute the performance of cement slurry. Therefore, in order to improve the anti-pollution ability of shale gas cementing cement slurry, the indoor research on improving the anti-pollution performance of shale gas well cementing cement slurry with surfactant AFSG-1 was carried out with on-site oil-based drilling fluid and cementing cement slurry as the research object. The results show that the addition of on-site oil-based drilling fluid will seriously affect the fluidity, thickening time and slurry water mud properties of cementing cement slurry. The greater the proportion of oil-based drilling fluid, the more serious the pollution is; With the increasing amount of surfactant AFSG-1 in the cementing cement slurry, the anti-pollution ability of the cement slurry is gradually enhanced. When the mass concentration of surfactant AFSG-1 in the cementing cement slurry reaches 2%, and then 20% oil-based drilling fluid is added, the fluidity, thickening time and cement stone properties of the slurry are significantly improved compared with those without surfactant. In addition, the effect of surfactant afsg-1 on improving the oil-based drilling fluid pollution resistance of cementing cement slurry is significantly better than that of other commonly used surfactants. The results show that surfactant AFSG-1 can effectively improve the anti oil-based drilling fluid pollution ability of shale gas cementing cement slurry, improve cementing quality and ensure cementing safety.

  • 1
• Corrosion mechanism and performance evaluation of inorganic blockages by neutral chelating system

  Qu Ming, Hou Jirui

  Abstract: (757) HTML (0) PDF (0.00 ByteKB) (1170)

  Abstract:

  Acidizing plugging removal technology is often used to solve the problems of reservoir pollution and lack of liquid supply caused by long-term development of carbonate reservoirs. Due to conventional acidizing technology is special for carbonate reservoir, the conventional acidification technology is prone to water lock, corrosion of pipe string and wellbore scaling in the production process, leading to reservoir damage and reducing reservoir productivity. Therefore, this paper developed a neutral chelating system to remove inorganic plugging without backflow and secondary damage to the formation. Composing of chelating agent EDTA and corrosion inhibitor PAA, and a small amount of stabilizer Na2SO3 was added. It was prepared by deionized water fusion filtration, dehydration grinding and grinding at 120℃ and roasting activation at 500℃. The experimental results show that the system has good corrosion ability for inorganic plug such as Ca2+、Mg2+ ion, the corrosion rate is up to 95% within 24h at normal temperature. The corrosion rate of N80 steel is 4.45g/m2·h after 12h at 90℃. The average dissolution rate of natural carbonate cores can achieve more than 70%. Therefore, neutral chelation plugging removal system has a good potential for field application.

  • 1
• Viscosity Prediction Model for Water-in-Oil Emulsion Based on Quantitative Characterization of Crude Oil Physical Properties

  LUO Haijun, WANG Zhihua

  Abstract: (783) HTML (0) PDF (0.00 ByteKB) (1108)

  Abstract:

  Eight kinds of crude oils with different physical properties were used to prepare water-in-oil (W/O) emulsions. The viscosity characteristics of the W/O emulsions were measured by rheometer. The effects of temperature, water cut of emulsion and shear rate on the apparent viscosity of W/O emulsions were studied. The results show that the apparent viscosity of the W/O emulsion decreases with the increase of temperature, increases with the increase of water cut, and decreases with the increase of shear rate, showing the property of shear thinning. The power law model was used to describe the rheological properties of W/O emulsion, i.e, . With the increase of water cut of emulsion, the consistency coefficient K of W/O emulsion increased gradually, while the rheological property index n decreased gradually. With the increase of temperature, the consistency coefficient K decreased gradually, while the rheological property index n increased gradually. Based on the experimental data and quantitative characterization of crude oil physical properties, a viscosity prediction model for W/O emulsion was established which could be applied to different crude oil and different shear conditions. The prediction deviation of the model shows that the average relative deviation between the calculated viscosity value and the measured viscosity value is 8.1%.

  • 1
• Development and field application of anti-returning and plugging agents

  Zeng Guang, Wan Xiumei

  Abstract: (720) HTML (0) PDF (0.00 ByteKB) (1119)

  Abstract:

  Aiming at the characteristics of shale gas plugging in Sichuan-Chongqing block, easy to blow back and high requirements for pressure, this paper developed a kind of ARP anti-return leakage plugging agent based on high softening point resin. It has the ability of deformation, cementation and curing. It can be used in combination with bridge plugging particles to cement and solidify with plugging agent particles in formation cracks to improve pressure bearing capacity and anti-return ability. The laboratory evaluated the dispersibility of the ARP plugging agent in the field oil-based drilling fluid and the bonding strength with the field leakage plugging agent, and tested the pressure bearing capacity and anti-return ability after the cementation was cured. According to the needs of field application, the density of ARP anti-return leakage plugging agent is determined to be 1.8g/cm3, the particle size is 0.5-2mm, and the optimal ratio is formed with the field plugging agent. That is, ARP anti-return leakage plugging agent accounts for 25 parts, and on-site leakage plugging agent accounts for 75 parts, and its bonding strength can reach 7.8MPa. When plugging 2-3mm natural cracks, the positive pressure can reach 8MPa, and the anti-reflection ability can reach 3.3MPa. At the same time, the on-site construction process is designed according to the material characteristics, and a good on-site application effect is achieved.

  • 1
• The corrosion inhibition performance and mechanism analysis of phenyl and benzoyl thiourea in hydrochloric acid

  Yu Yi

  Abstract: (715) HTML (0) PDF (0.00 ByteKB) (1199)

  Abstract:

  The inhibition performance and mechanism of two thiourea-based derivatives, phenylthiourea (PHTU) and benzoylthiourea (BOTU) for 20# steel in 15% HCl solution were investigated by corrosion weight loss experiments, scanning electron microscope (SEM), and quantum chemical calculations. The results indicated that both PHTU and BOTU showed good inhibition performance for 20# steel in 15% HCl solution, and the corrosion inhibition rate could reach more than 83% at 2 mmol/L. The adsorption of PHTU and BOTU on the steel surface was in accordance with the Langmuir adsorption model, and the adsorption model was a mixed physical and chemical adsorption. Quantum chemical calculations results showed that the reactive sites in the corrosion inhibitor molecule were mainly distributed in the C=S double bond, C-N bond and the C=O double bond. The N atoms in the corrosion inhibitor can form physical adsorption with the steel surface through electrostatic gravity after being protonated by the acid. The high electron cloud density of C=S bond, C=O bond and phenyl group can provide electrons to form chemisorption with the empty d orbitals of iron atoms through coordinate and feedback bonds, which can then be stably adsorbed on the metal surface to form a protective film and inhibit the corrosion process.

  • 1
• Development and Function Mechanism of High Temperature Resistance Intercalation Adsorption Inhibitor

  Wang Xiao-Jun

  Abstract: (578) HTML (0) PDF (0.00 ByteKB) (1375)

  Abstract:

  High temperature resistance intercalation adsorption inhibitor has been developed for ?reducing wellbore instability caused by which conventional inhibitors could not controll effectively hydration of clay surface, There are a lot of strong adsorption groups and hydrophobic groups in the molecular structure of the new inhibitor, which was low molecular weight, non-toxic environmental protection and good thermal stability. The analysis of inhibition mechanism showed that, the new inhibitor,the electrostatic repulsion and short-range repulsion of surface hydration of clay can be effectively reduced by the combination of strong adsorption group and exchange of hydrated sodium ions.And by changing the surface tension and wettability of clay, the self-imbibition capacity and specific hydrophilicity of shale can be controlled, and the invasion of water phase can be reduced. Meanwhile.?the new inhibitor had strong adsorption and anti-desorption ability, could adsorb on the clay surface for a long time, improved the hydrophobicity of the clay surface, and reduced the invasion of free water. Laboratory evaluation experiments showed that the new inhibitor had good properties of inhibiting mud production, controlling clay hydration expansion and preventing mud shale collapse, which was beneficial to the stability of rheological property and borehole wall of water-based drilling fluid, it had a good application prospect.

  • 1
• Laboratory study on solid-free constant rheological drilling fluid with reservoir protection for deep-water drilling

  Chen Liang, You Fu-chang.

  Abstract: (475) HTML (0) PDF (0.00 ByteKB) (1225)

  Abstract:

  In the drilling process of deep-water oil and gas fields, due to the low temperature near the bottom mud line, it was easy to lead to the thickening, paste plugging, slurry running and other problems of drilling fluid. The thermosensitive thickening copolymer ASSN was prepared with acrylamide, N-vinyl caprolactam, diethylbenzene and sodium allyl sulfonate as raw materials. ASSN was combined with fenugreek gum , which had strong salt resistance and significant cutting effect, to form a flow pattern regulator with low temperature constant rheological properties, and formed a set of solid-free constant rheological drilling fluid with reservoir protection for deep-water drilling with other treatment agents. 0.5%ASSN+0.3% fenugreek gum as flow pattern regulator played a good role in regulating the rheological properties of drilling fluid at low temperature. Its low temperature control ability of drilling fluid was less affected by different weighting agents, and it had good compatibility with other drilling fluid treatment agents, so that the FLAPI of drilling fluid was only 5.2mL. And it had good resistance to contaminated soil, field drilling cuttings, salt and seawater intrusion and excellent reservoir protection (recovery value of field core permeability was greater than 95%).

  • 1
• Synthesis and Performance Evaluation of an Amphoteric Polymer Viscosity Reducer

  ZHANG Cheng, DUAN Ming

  Abstract: (691) HTML (0) PDF (0.00 ByteKB) (1399)

  Abstract:

  In this paper, acrylic acid (AA), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), and methacryloxyethyl trimethylammonium chloride (DMC) wereSusedSasSmonomers, based on the aqueous solution explosion polymerization process, a low molecular weight zwitterionic polymer viscosity reducer for drilling fluids was synthesized by using environmentally friendly tetramethylthiuram disulfide (TMTD) instead of sulfhydryl compound as the chain transfer agent. Taking the room temperature viscosity reduction rate as the evaluation index, the optimum synthesis conditions of the viscosity reducer have been determined: the monomer concentration was 55 wt%, the addition of TMTD was 0.75 wt%, the addition of oxidation-reduction initiator was 3 wt% of the monomer concentration, the neutralization of (AA+AMPS) was 50%, the addition of AMPS was 5.5 wt%, and the addition of DMC was 4.5 wt%. Under this condition, the number average molecular weight of the synthesized zwitterionic polymer viscosity reducer is 914 g/mol, and its viscosity reduction rate in the fresh water base slurry is 91.53%, and it has good temperature resistance, which can meet the temperature resistance requirement of 180 ℃. This research provides a green and environmentally friendly option for the synthesis of low molecular weight zwitterionic viscosity reducer.

  • 1
• Effects of CO₂ on the Aggregation Behaviorof Asphaltene Molecules in Heavy Oil

  JIANG Huixin, WANG Chuangye

  Abstract: (519) HTML (0) PDF (0.00 ByteKB) (1809)

  Abstract:

  The aggregation behavior of asphaltenes significantly affects the viscosity of heavy oil. Studying the aggregation behavior of CO2 on asphaltenes in heavy oil can further analyze the mechanism of CO2 displacement. Under different CO2 pressures and conditions, CO2 dissolution experiments were carried out on heavy oil and heavy oil added with benzene and ethanol as CO2 solubilizers. After separating the four components, CO2-treated asphaltenes were obtained. X-ray diffractometer, scanning electron microscope, transmission electron microscope and other analytical instruments were used to characterize the interlayer spacing, surface morphology and microstructure of asphaltene aggregates extracted under different experimental conditions, and the effect of CO2 on asphaltenes in heavy oil was analyzed. Influence mechanism of aggregation behavior. The results show that the dissolution of CO2 in heavy oil leads to an increase in the interlayer spacing of asphaltene aggregation stacking, which slows down the aggregation behavior of asphaltene molecules, thereby reducing the viscosity of heavy oil.

  • 1
• Research progress and prospects of lubricants in water-based drilling fluid

  WANG Kai, LI Xiaoming

  Abstract: (884) HTML (0) PDF (0.00 ByteKB) (1170)

  Abstract:

  A great number of researches about eco-friendly and high-performance lubricant have been conducted to improve the lubrication of water based drilling fluids, solving the high friction of long horizontal section of horizontal wells and promoting the development of drilling technology for horizontal well. In this paper, the domestic and international research progress of lubricant for water based drilling fluids has been reviewed including the lubricants from alcohol ether, alkyl glycoside, modified vegetable oils, mixed lubricants, extreme-pressure lubricants, and encapsulated lubricants. The advantages and disadvantages of these lubricants are compared and the outlooks for the development of water based drilling lubricants are expected.

  • 1
• Laboratory Screening and Evaluation of Surfactant Flooding System with Salt Resistance

  ZHOU Ming

  Abstract: (626) HTML (0) PDF (0.00 ByteKB) (1183)

  Abstract:

  Aiming at the problems of unsatisfactory injection production ratio in the actual oil production and development process of Yanhua 182 Well Group, low production and low energy of development wells, high salinity, high calcium and magnesium ions in formation water resulting in the failure of conventional surfactant, a system of surfactant flooding with anti-salt was prepared. Without chelating agent and stabilizer, the system of surfactant flooding consisted of PPM-12（bis{[(N-methylN-(3- dodecanoxy-2-hydroxyl) propyl-N-(2-hydroxyl-3-sulfonic acid sodium) propyl] methylene} ammonium chlorides），AES-12 (sodium lauryl ether sulfate) and OB-2 (dodecyl dimethylamine oxide). The optimum total concentration of surfactant flooding system was 0.3wt%, and the suitable weight ratio range was 4:1:1-1:1:4. The optimum ratio is 2:1:3, and the oil-water interfacial tension can reach the lowest value (0.0012 mN.m-1). The adsorption, emulsification, salt resistance of the composite surfactant flooding system was studied under optimum conditions. The results of adsorption performance showed that the system was still in the order of 10-3 mN.m-1 after six adsorption. The results of emulsification showed that the water separation time of the system was 3995s. The experimental results of resistance to sodium, calcium and magnisesium ions showed that the system could reach the order of 10-3 mN. m-1 in the range of sodium, calcium and magnesium ions in the oilfield. Magnesium ions have the greatest influence on the interfacial tension of the system, followed by calcium ions and sodium ions. Experiments show that the PPM-12, AES-12 and OB-2 compound system is suitable for EOR of Chang 6 reservoir of Hua 182 well groups, with an average EOR of 10.3%. It has a good application prospect in similar high salt and low permeability reservoirs.

  • 1
• Synthesis and performance study of the high temperature-resistant acid gelling agents

  LI hui, LUO bin

  Abstract: (584) HTML (0) PDF (0.00 ByteKB) (1150)

  Abstract:

  Compared with other acid gelling agents, amphoteric gelling agents have the advantages of low price and convenient synthesis and can improve the viscosity of acid based on supramolecular effect of gelling agents. Hence, amphoteric gelling agents have wild application prospect in acidizing fracturing field. Two amphoteric gelling agents were synthesized from acrylamide (AM), 2-acrylamide-2-methylpropanesulfonic acid (AMPS), dimethyl diallyl ammonium chloride (DMDAAC) and methacryloyloxyethyl trimethyl ammonium chloride (DMC) by free radical aqueous solution polymerization. The results indicated that acid dissolving time of two amphoteric gelling agents less than 40 min. The viscous acid containing the compound of two amphoteric gelling agents mixed in a certain mass ratio was 39 mPa·s at room temperature (25°C) and 170S-1and was 15 mPa·s at 160°C and 170S-1 after continuous shear for 90min, which demonstrated that the compound had excellent viscosity increasing property, temperature resistance and shear resistance performance

  • 1
• The effects of wettability on water coning in bottom water reservoirs

  HU junjie, ZHANG guicai

  Abstract: (463) HTML (0) PDF (0.00 ByteKB) (1241)

  Abstract:

  The wettability of the rock has an important influence on the delay of the water coning recovery after the bottom water reservoir is pressed, but the degree of its influence is not clear. In view of this, four wetting adjustment systems with different wetting abilities were constructed with the contact angle as the index of wetting agent, which were dissolved in oil-soluble viscosity reducer, and their properties were evaluated. On this basis, the intrinsic relationship between wettability and production property conditions was quantitatively described, and the degree of influence of wettability on inhibiting water coning recovery was further illustrated. The results show that the reservoir under the action of oil wetting agent has the best effect of inhibiting bottom water recovery, the equilibrium pressure ratio reaches 3.75, and the net recovery degree increases by 15.17%. However, the equilibrium pressure ratio of the reservoir under the action of strong water wetting agent is only 0.54, and the net recovery is increased by 6.51%. There is an obvious regularity between wettability and produced physical properties. Adjusting the wettability of the reservoir can effectively restrain the rise of the water cone and improve the oil recovery.

  • 1
• Development and application of micro-expansion degradable gel temporary plugging agent for acid fracturing

  WU Wenchuan, YU Xiaorong

  Abstract: (837) HTML (0) PDF (0.00 ByteKB) (1240)

  Abstract:

  Diversion acid fracturing is one of the effective measures to increase production of carbonate reservoir. Importantly, the key of this technology lies in the temporary plugging agent. However, the existing acid fracturing with temporary plugging agents are of poor acid resistance, complicated removal process, and high cost. Aiming at solving those problems, a micro-expansion temporary plugging agent (WDS) for acid fracturing was prepared through aqueous radical polymerization in this study. The degradation performance, temporary plugging performance, and reservoir damage of the WDS were studied, and it was applied in field construction. The results showed that it was first micro-expanded and then degraded in different solutions. The complete degradation time of the WDS reduced from 78 h to 45 h with the rising temperature from 70 ℃ to 120 ℃. The complete degradation time reduced from 75 h to 48 h with the rising concentration of HCl from 3% to 20%. According to the results of displacement experiment, with the increase of the injection, the temporary plugging pressure increased, and the time to reach the maximum temporary plugging pressure reduced. And with the increase of the fracture width, the temporary plugging pressure decreased, and the time to reach the maximum temporary plugging pressure increased. In addition, the WDS was less harmful to the core, and the permeability recovery value of cores of more than 90%. Furthermore, the field application results indicated that the construction pressure increased by 10 MPa after adding the WDS, and the effect of temporary plugging was remarkable. In conclusion, the WDS can be completely degraded under the conditions of temperature, acid, and salinity, and the effect of temporary plugging is remarkable. It has a good application prospect in diverting acid fracturing.

  • 1
• Synthesis, Characterization and Drag Reduction Properties of a Long-chain End-group Hydrophobically Associative Polymer

  YANG LIN

  Abstract: (612) HTML (0) PDF (0.00 ByteKB) (1198)

  Abstract:

  In order to develop a new type of slick water drag reducer, this paper uses terpolymer of acrylamide (AM), hydrophobic monomer dodecyl dimethylallyl ammonium chloride (C12DMAAC), and sodium acrylate (NaAA) as raw materials. The long-chain end-group hydrophobic associative polymer HPAM-L was synthesized by the self-made long-chain hydrophobic initiator AIBL. The performance was characterized, and the friction resistance of HPAM-L solution at different concentrations was measured by a flow loop friction tester. The results show that the viscosity-average molecular weight of HPAM-L is about 7.43 × 106 g/mol, the critical association concentration is about 1～1.5 g/L, and it has good temperature resistance and shear stability. The aqueous solution of HPAM-L has a wide range of Linear viscoelastic region, and the higher the concentration, the more obvious the elastic characteristics. When the solution concentration is 0.075%, 0.086%, 0.1% and 0.15%, the maximum drag reduction rate can reach 71.6%, 73.1%, 73.3% and 74.1%, respectively, and the drag reduction performance is good.

  • 1
• Analysis of Factors Affecting Silicon Removal by Hydroelectric Flocculation Depth in Ultra-heavy Oil Production

  YANG Changgen, FAN Yuxin

  Abstract: (669) HTML (0) PDF (0.00 ByteKB) (1173)

  Abstract:

  Electrocoagulation has been treated by experiment on deep silicon removal of super-heavy oil produced water using aluminum plates as cathode and anode. The optimal PAC dosage, pH value ,current density and PAM dosage are obtained through single factor variables. The results show that single electrocoagulation can not achieve deep silicon removal. Electrocoagulation together with PAC and PAM has a synergistic effect on the removal of silicon from super-heavy oil produced water. The effluent of SiO2 by electrocoagulation reaches 20mg/L and the SiO2 removal rate is 92% when the PAC is 200mg/L, the pH is 8.0, the current density is 10mA/cm2, and electroflocculation time is 13 minutes, which can achieve deep silicon removal. With the increase of electric flocculation time, the removal rate of SiO2 increases, but the rate of change decreases.

  • 1
• Synthesis and demulsification performance evaluation of nano iron sol stabilized by biosurfactant

  ZOU Jing, WANG Zhengliang

  Abstract: (591) HTML (0) PDF (0.00 ByteKB) (1220)

  Abstract:

  In view of the high cost and pollution of physical and chemical demulsifiers in the demulsification process of oilfield wastewater, it is necessary to study and synthesize new environmentally friendly demulsifiers. In this paper, a combination of sol-gel and solvothermal method is used to prepare biosurfactant (Biosurfactant, BS) stabilized nano-iron sol materials, to study the optimal BS concentration, and use SEM, XRD, FTIR, laser particle size analyzer, Zeta Potential etc. characterize the BS-stabilized nano-iron sol, and study its morphology, size, phase, functional group, sol stability, particle size distribution and other influencing factors. The demulsification performance of the synthesized nano-iron sol on the oily sewage emulsion prepared by the oil-water mixture on Weizhou Island was investigated. The results showed that after fermentation of the glycolipid biosurfactant T bacteria with a specific medium for 6 days, the supernatant after centrifugation was taken to synthesize iron sol. When the concentration of supernatant was 80 % and 100 %, iron particles with diameters of about 200 nm and 40 – 200 nm could be synthesized, respectively. When the concentration was 60 %, the demulsification effect of nano-iron sol product was the best. At low temperature, it could produce good demulsification effect on the oil-in-water emulsion formed by sodium dodecyl sulfate, and the dehydration rate reached 78 % after 24 h. It shows that the method used in this paper can synthesize BS stable nano-iron sol with good demulsification characteristics. It is suggested that biological metabolites and chemical agents should be combined organically in the future to prepare environmentally friendly composite nano-demulsifiers, while studying its repeated use and other issues.

  • 1
• Measurement of relative permeability curve of heavy oil - water by nuclear magnetic resonance

  Pu Wanfen, Chang Jiajing

  Abstract: (693) HTML (0) PDF (0.00 ByteKB) (1758)

  Abstract:

  Relative permeability was an important basic measurement parameter in heavy oil development experiment. Due to the high viscosity of heavy oil, oil-water emulsification was prone to occur during water flooding process, which made it difficult to obtain the heavy oil-water relative permeability curve accurately. The traditional measurement method of relative permeability curve regarded the core as a "black box", and measured the volume of oil and water at the outlet by the method of manual reading or weighing, which had the disadvantages of low measurement accuracy and less information. In order to accurately measure the heavy oil-water relative permeability curve, this paper selected the long artificial sandstone core. Based on the nuclear magnetic resonance measurement technology, through the simultaneous calibration of crude oil and formation water of Bohai B reservoir, the unsteady state method was used to measure the heavy oil-water relative permeability curve, and the T2 spectrum test was carried out on the core and the produced fluid at the outlet. Thus, the pore volume (147.18cm³), irreducible water saturation (25.9%), residual oil saturation (43.83%) of the core and the oil and water content at the outlet were obtained more accurately, and the heavy oil-water relative permeability curve was obtained more accurately. Moreover, the D/T2 two-dimensional spectrum test was carried out on the produced fluid with oil-water emulsification, and the emulsification of oil and water was judged more accurately. The research results can provide some theoretical guidance for the development of heavy oil water flooding, which is beneficial to the study of the mechanism of heavy oil water flooding.

  • 1
• Preparation and Performance Evaluation of Depressurization and Oil-displacing Agent in Low Permeability Reservoir

  QU Huimin

  Abstract: (769) HTML (0) PDF (0.00 ByteKB) (1382)

  Abstract:

  Affected by reservoir physical properties, there is a contradiction between the insufficient formation energy and difficult water injection in water flooding development of low permeability reservoirs. On the one hand, the water injection pressure is high and the underinjection is serious. On the other hand, the formation pressure drop of low permeability reservoirs is large, the productivity decreases rapidly, and the oil recovery rate and recovery degree are low. After water flooding, there are still many forms of residual oil such as membrane or oil droplets. In view of the above problems, this work synthesized metronidazole asymmetric Gemini surfactant, and combined with dehydro rosin surfactant, cetyl alcohol, ethanol to form a functional enhanced injection and oil displacement agent. The agent reduces the interfacial tension between oil and water, emulsifying crude oil and removing oil film. The cationic component forms molecular film on the rock surface with water as the transfer medium, stabilizes clay, improves the wettability of rock surface and reduces water injection resistance. Combined with the field test of pressure flooding, the daily oil increment of the well group is 13.4 t/d at the beginning and 12.6 t/d after 5 months. The injection capacity of the well was significantly improved. Before pressure flooding, the injection volume of the water well is 0 at the high pressure of 30 MPa, and 30 m³/d at 27.5 MPa after pressure flooding.

  • 1
• Plugging Mechanism and Prevention of Oil Well in Polymer Flooding Reservoir

  LIU Ying, WANG Zengbao

  Abstract: (570) HTML (0) PDF (0.00 ByteKB) (1306)

  Abstract:

  Polymer flooding widely used in oilfields for a long time corresponds to serious plugging of oil wells and decreased liquid volume, which seriously affects the further development of reservoirs after polymer flooding. Using XRD, SEM and other technical means to analyze the composition and composition of oil well plugging products; through different plugging fluid simulation and near-well reservoir condition simulation, the plugging degree and main controlling factors of oil well plugging are studied. The results show that the plugs in the oil wells of polymer flooding reservoirs are mainly polymer aggregates that are cross-linked and embedded to adsorb formation mineral salts and clays, accounting for 65.6%; followed by formation sand particles and cements, and crude oil, respectively, 17.8 %, 16.6%. The plugging of porous media caused by the formation of sand particles is the main controlling factor of plugging near the oil well. The polymer agglomerates formed by polymer derivative cross-linking and adsorption agglomeration aggravate the degree of blockage of the oil well. Based on the guidance of the research on the plugging mechanism of polymer flooding reservoirs, the near-well crude oil cleaning of plugged oil wells + the oxidative degradation of polymer micelles, the integrated prevention and control program of oil well plugging and sand control for the effective sand consolidation control of far wells has good application effects, and the average single well extraction 86.8%.

  • 1
• The Effect and Mechanism of Surfactants with Different Interfacial Properties to Improve Oil Recovery

  LIU Qian

  Abstract: (509) HTML (0) PDF (0.00 ByteKB) (1461)

  Abstract:

  Taking the low permeability tight reservoir of Chang 6 as the research object, two self-made surfactants S1 (with strong modification wettability) and S2 (ultra-low interfacial tension) with different interfacial properties were selected. Their static and dynamic permeability effects were characterized by NMR, and their oil displacement process was studied by 2.5-dimensional micro model, The EOR effect and mechanism of surfactants with different interfacial properties are analyzed. The results show that both S1 and S2 have good enhanced production effects. Imbibition is a process in which water enters small pores to replace oil to large pores. Surfactants can greatly promote the production of small pores; During oil flooding, the dominant channel is obviously formed, which can realize wettability reversal, and has additional imbibition effect, which greatly increases the sweep volume and oil washing efficiency, and can disperse the crude oil into small scale state. Among them, the S1 capillary with stronger wettability ability is more powerful and has a higher degree of mobilization of small holes, but the recovery rate is slower, but the additional imbibition during displacement is stronger, which can achieve ultra-low interfacial tension.The S2 with ultra-low interfacial tension can achieve smaller oil phase flow resistance, faster imbibition speed, and faster recovery to reach equilibrium.

  • 1
• Accelerating the dissolution of hydrophobically associative polymers by Cyclodextrin

  李玺

  Abstract: (831) HTML (0) PDF (0.00 ByteKB) (1356)

  Abstract:

  Hydrophobically associating polymers are highly concerned for their excellent rheological performance. However, the poor dissolution caused by the interactions of hydrophobes restricts their popularization and application on oilfields. Irreversible viscosity loss of polymer solution will inevitably occur through the current physical accelerated dissolution modes. In this paper, cyclodextrins (CDs) are used to accelerate the dissolution of the hydrophobically associating polymer by the inclusion of hydrophobic groups, and avoiding solution viscosity loss. The inclusion of cyclodextrins on hydrophobes improves the interaction of associating polymers with solvents, and as the molar ratio of cyclodextrin to hydrophobic groups (CD: [H]) increases, the dissolution time of the hydrophobically associating polymer decreases exponentially. Rheology results have shown that CDs can significantly shorten the dissolution time of the hydrophobically associating polymers by disrupting association structures of hydrophobic groups through inclusion. Utilizing the competitive inclusion properties of cyclodextrin inclusion complex, the rheological properties of the solution can be completely restored by adding an appropriate amount of nonionic surfactants with stronger affinity to the CDs to the hydrophobes of associating polymer.

  • 1
• Performance evaluation and application of the microbial huff and puff system for Sheng li oil field Luo 9 Shi 1 block

  CAO Gongze, LI Caifeng

  Abstract: (582) HTML (0) PDF (0.00 ByteKB) (1276)

  Abstract:

  Luo 9 Shi 1 block has some problems of high temperature, high viscosity, high water cut and low water flooding efficiency.In order to improve the output of high water cut oil well, the composite system of biological polysaccharide and microorganism was developed. Its temperature resistance, plugging performance, emulsion viscosity role and model of the displacement effect were studied. Finally, the composite system of huff and puff was applied in the field.The results showed that the viscosity of the new biological polysaccharide remained in the range of 120 ~ 125mPa.s at 55 ~ 95℃ and the temperature resistance was strong.When the new biological polysaccharide injected into the core, the pressure increases by 5.6 times and the permeability decreases by 53.3%, which could effectively seal the core.When the ratio of microbial fermentation liquidⅠto microbial fermentation liquidⅡwas 1:2, the high temperature emulsification ability was the strongest and the emulsification viscosity reduction rate was 81.4%. The physical simulation of oil displacement experiment showed that the composite system of biological polysaccharide and microorganism improved oil recovery by 13.9%, which was better than the single system in oil displacement. The application results of five oil Wells showed that four oil Wells had achieved success and the cumulative increase of oil amounted to 2730t. The effect of increasing oil and dewatering was significant, which continued to be effective.It effectively improved the low efficiency of oil well in Luo9 Test 1 block.

  • 1
• Development and Evaluation of cryogenic Microbial Demulsification System in shale oil production fracturing fluid

  Gong Zhaobo, Ma Ting

  Abstract: (1362) HTML (0) PDF (0.00 ByteKB) (1304)

  Abstract:

  In order to meet the demand for demulsification in Xinjiang oilfields, and reduce the environmental pollution of common oilfield chemicals, this article based on environmental safety and the complex situation of shale oil fracturing produced fluids in the Madong block in Xinjiang, and fifteen kinds of biodemulsifiers synthesized by microbial fermentation were screened and evaluated by the bottle test method. The demulsification of the fermentation broth and the purified extract was compared, and the results showed that the biodemulsifier XJ-4-2 synthesized by the XJ-4 bacteria had good compatibility with the extracted fluid from the Madong block and more than 80% dehydration rate. In order to improve the demulsification efficiency and reduce the cost, a composite system of biological demulsifier and conventional chemical demulsifier is adopted. After optimization, the demulsification efficiency of the composite system of biological demulsifier XJ-4-2 and chemical polyether demulsifier reaches above 95％. Through the optimization of the dosing process, the initial water content is 43.76%. When the chemical demulsifier 200mg/L is added at 60 ℃, the dehydration rate after 2h sedimentation is 91.45%, the remaining water content ratio of crude oil was 8.43%, and the oil content ratio of sewage is 228mg/ L. The initial water content of the improved crude oil is 33.85%. At 50 ℃, when the compound formula 200mg/L is added, the dehydration rate after 2h sedimentation is 94.56%, the remaining water content ratio of crude oil 1.84%, and the oil content ratio of sewage is 156mg/L. In summary, the biological demulsifier has high dehydration rate at low temperature and low sewage oil content. It is of great significance for the efficient separation of produced fluids from fracturing exploitation of shale oil in the Madong block and ensuring the normal operation and economic benefits of the oilfield.

  • 1
• Static Adsorption of JCP-1 Nano-spheres on Mineral Surface in Liquid Phase

  JIANG Xu, CHEN Junbin

  Abstract: (465) HTML (0) PDF (0.00 ByteKB) (1184)

  Abstract:

  Nanospheres have been widely used in low permeability reservoir development. In order to study the adsorption mechanism of nano-spheres on rock and mineral surfaces, it is necessary to quantitatively characterize the influence of mineral types on the adsorption capacity of nano-spheres on rock and mineral surfaces. Firstly, starch - cadmium iodide method was used to calibrate the concentration of JCP-1 nano-microsphere emulsion, and then the adsorption capacity of the microspheres on the surface of single component mineral and multi-component mineral was determined respectively. Then, based on the measured data of microsphere adsorption on the surface of single component minerals, the predicted value of microsphere adsorption on the surface of multi-component minerals was obtained by weighted superposition according to the relative content of rock minerals. The results show that the static adsorption capacity of JCP-1 nanospheres on different mineral surfaces varies greatly. The adsorption capacity of clay minerals to microspheres is generally stronger than that of non-clay minerals. Kaolinite has the strongest adsorption capacity for this type of microspheres, which is 14.75 times stronger than quartz. The adsorption capacity of the microspheres on the surface of potash feldspar is much stronger than that of the other two non-clay minerals, and the variation value of adsorption capacity is 1.96 times and 8.42 times of that on the surface of albite and quartz, respectively. For the adsorption capacity of microspheres on the surface of multi-component minerals, the relative error between the predicted value of weighted superposition method and the measured value is within 3%. Finally, based on the adsorption phenomenon at solid-liquid interface during the migration of nanospheres in pore channels, it is considered that the clay minerals on the pore walls strengthen the adsorption of microspheres, which is beneficial to change the pore radius and achieve "partial fluid flow direction" under the condition of "incomplete plugging".

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• Cationic Surfactant Pretreats Formation to Enhance Squeeze Life of Scale Inhibitor

  SONG Haojun, REN Shaoran

  Abstract: (463) HTML (0) PDF (0.00 ByteKB) (1228)

  Abstract:

  In the process of seawater injection development in offshore oilfields, the incompatibility of injected water and formation water often leads to serious sulfate scaling in oil wells. Although the squeeze treatment can be used to prevent scale, the squeeze life of the scale inhibitor is generally shorter. This article considers adding an adsorption enhancer to the pre-flush to increase the adsorption capacity of the scale inhibitor in the formation and reduce the desorption speed of the scale inhibitor. Quaternary ammonium surfactant DTAC and cationic gemini surfactant GS-A6 were selected as adsorption enhancers, and sodium polyacrylate PAAS was selected as scale inhibitor. The compatibility experiment, static adsorption experiment and dynamic adsorption-desorption experiment of adsorption promoter and scale inhibitor were carried out. The results show that at 120℃, the two adsorption enhancers have good compatibility with the scale inhibitor, and the adsorption enhancer can effectively increase the adsorption amount of the scale inhibitor in the formation and prolong the squeeze life of the scale inhibitor. The adsorption enhancer DTAC was greatly affected by oil saturation, and the adsorption enhancement effect decreased significantly at high oil saturation. The adsorption enhancer GS-A6 has a stable adsorption enhancement effect under different concentrations and different oil saturation conditions, and is suitable for oil well scale inhibition in different development stages.

  • 1
• Integrated Thickener with High-Viscosity and High-Drag Reduction used for Fracturing Deeper Shale Gas

  WEI Juanming

  Abstract: (796) HTML (0) PDF (0.00 ByteKB) (1287)

  Abstract:

  Slick water hydrofracking represents an important technique for the efficient development of shale gas, but there are a series of challenges such as low viscosity, large freshwater consumption and slick water-to-gel transition, which limit its application in hydrofracking of deeper (>3500 m) shale gas reservoirs. To address these issues, an integrated thickener with high-viscosity and drag reduction (HVFR) was synthesized by free radical polymerization, and their solubility, thickening ability, drag reduction and proppant carrying capability as well as heat- and shear-resistance were examined. The results showed that the viscosity-average molecular weight of HVFR is 22.7 x 10^6 g/mol, and the HVFR exhibited a rapid dissolution rate with thickening rate of 93% within 1 min, which is conducive to the online continuous mixing of fracturing fluid. At a flow rate of 150 L/min, the drag reduction can reach higher than 70% for both low- and high-viscosity slick water, and up to 68% for gel. It is also demonstrated that HVFR thickener exhibited multifunctional properties and can be freely transited between low- and high-viscosity slick water as well as gel by altering the concentration of HVFR. The cross-linked fracturing fluid based on HVFR displayed not only remarkable heat- and shear-resistance, but also proppant carrying capacity. The viscosity of the cross-linked fracturing fluid can be maintained at 120 mPa*s after shearing for 120 min at 120 oC and 170 s^(-1).

  • 1
• Performance evaluation of low density elastic sealing cement slurry to improve the sealing capacity between cement layers

  XING Xuesong

  Abstract: (607) HTML (0) PDF (0.00 ByteKB) (1259)

  Abstract:

  Abstract: Under the existing cementing slurry technology, ensuring the long-term stability of wellbore integrity is facing challenges, especially the conventional low-density slurry. After perforation, the integrity of cement stone is damaged more seriously, resulting in sealing failure, poor cementing quality between cement stone and casing and well wall, and channeling is easy to occur. In view of the above problems, it is preferred to use compound liquid fiber to improve the strength and toughness of cement paste, nano lightening agent to improve the settlement stability of cement slurry, and 10% res-1 elastic material is preferred to reduce the elastic modulus of cement paste and improve the deformation capacity of cement paste. The comprehensive performance evaluation of low-density elastic sealing cement slurry was carried out in the laboratory. The results show that the 1.5g/cm3 low-density elastic sealing cement slurry system has good rheology, adjustable thickening time of cement slurry, water loss less than 50ml, and linear expansion rate of 0.45%, which can effectively inhibit the generation of micro annulus and micro gap. Compared with ordinary low-density cement slurry, the permeability and elastic modulus of low-density elastic sealing cement slurry are reduced by 69.5% and 78.4% respectively, and the compressive strength and flexural strength are increased by 61% and 54% respectively, indicating that the cement slurry has good compactness, flexibility and elastic deformation ability. The evaluation of the sealing capacity of the cement sheath shows that under the conditions of alternating pressure range of 20mpa-40mpa and pressure rise and fall frequency of 5 times, the anti channeling strength in the simulated sealing is greater than 7 MPa/m2, which can effectively improve the long-term sealing capacity of the cement sheath and improve the cementing quality.

  • 1
• Research on the Mineralized Deposition of Nanoparticles and Its Application Exploration on the Improvement of Wellbore Stability

  Liu Zhendong

  Abstract: (568) HTML (0) PDF (0.00 ByteKB) (1249)

  Abstract:

  In the drilling of shale formation, the problem of wellbore stability is relatively prominent. Due to the special physical and chemical properties of shale, it is easy to absorb water and expand, resulting in the wellbore falling and collapsing, so it is necessary to reinforce the wellbore during drilling. In this paper,the process of biomineralization is simulated to study the self-assembly technology of nanoparticles. Based on the selection of cationic polymers and nanoparticles, this paper focused on the self-assembly deposition process of modified calcium carbonate and BPEI, as well as the structural analysis of the deposition layer. The experimental results displayed that modified nano-calcium carbonate could form a well deposition layer on the simulated well wall. In addition, this paper also explored the application of this technique on the improvement of wellbore stability which would provide a new strategy to solve the problem of wellbore instability.

  • 1
• Dynamic analysis and preparation of drag reduction and sand-carrying dual-functional polymer materials for shale fracturing

  ZHOU Cheng-yu

  Abstract: (561) HTML (0) PDF (0.00 ByteKB) (1287)

  Abstract:

  In order to solve the problems of large frictional resistance at the front end and low viscosity at the tail end of volumetric fracturing in shale reservoirs. The steric hindrance of twin tail monomers with different carbon chain lengths, mean square terminal distance and mean square displacement (MSD) of the polymer materials were studied based on molecular dynamics. The drag reducer LMA-AM-DiC12AM (LAD) was synthesized by micellar polymerization with Lauryl methlacrylate (LMA), Acrylamide (AM) and N,N-dodecyl acrylmaide (DiC12AM). The rheological properties, drag reduction and sand carrying properties of LAD solution were studied by rheometer and friction tester. The results show that DiC12AM monomer has small steric hindrance, the best chain flexibility of polymer materials molecules, the best ability to bind water molecules, and the great drag reduction potential. LAD has good shear stability (viscosity is 75mPa·s) and shear recovery performance. It can withstand a temperature of 60℃ at present. Its drag reduction rate reach 67.4%. The average sedimentation rate of 40/70 mesh ceramsite is 2.05×10-4 mm/s. The polymer materials agent has both drag reduction and sand carrying properties, which is basically consistent with the simulation results.

  • 1
• Application of the Nanoparticles Augmented Enhanced Oil Recovery

  ZHANG Xiaojun, GUO Jixiang

  Abstract: (1069) HTML (0) PDF (0.00 ByteKB) (1385)

  Abstract:

  Nanoparticles(NPs) are seen as potential solutions to overcome the challenges, such as low sweep efficiency, associated with these traditional EOR techniques. The application of nanoparticles augmented chemical EOR, gas EOR, and thermal EOR techniques in recent years have been summarized in this paper. The main principles, characteristics and research results of the nanoparticles augmented EOR process were introduced. Also, EOR challenges using NPs and the needed future research are highlighted. It provided foundation for the development of NPs augmented EOR technologies.

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• Development and performance evaluation of high temperature-resistant core-shell nano plugging agent used for oil-based drilling fluid

  Du Zhenghong, Peng Wu

  Abstract: (920) HTML (0) PDF (0.00 ByteKB) (1285)

  Abstract:

  Nano pores and micro fractures are well developed in shale formation. However, the particle size of conventional plugging agent is large and it is difficult to plug pores and fractures in shale. A high temperature-resistant core-shell nano plugging agent CLG-NM was prepared with inorganic nano silica as the core and poly (styrene-butyl acrylate-acrylic acid) as the shell. The plugging agent was characterized by infrared spectroscopy, transmission electron microscopy, dynamic light scattering and thermogravimetry, and its plugging performance was evaluated by shale pressure transfer experiment. The results show that the particle size distribution of CLG-NM is 40 ~ 300 nm, the median particle size is 89.4 nm. CLG-NM maintains thermal stability below 372 ℃. Furthermore, CLG-NM has good compatibility with oil-based drilling fluid. After 3% CLG-NM was added into the oil-based drilling fluid of Weiye 28-7hf well, the rheological property of the drilling fluid changed slightly. The high temperature and high pressure filtration (aging at 180^oC for 16h) decreased from 3.1mL to 2.8mL, and the demulsification voltage kept higher than 700mV. Compared with KC-2 and PT-seal, CLG-NM has better plugging effect on the nano pores and fractures in shale.

  • 1
• Research on Polyelectrolyte Hydrophobic Associated Composite Suspension Stabilizer for Cementing

  ZHAO Qiyang, CHEN Xuewen

  Abstract: (727) HTML (0) PDF (0.00 ByteKB) (1304)

  Abstract:

  In deep and ultra-deep oil and gas resource cementing, due to the high temperature of the formation, some admixtures in the cement slurry fail at high temperatures, resulting in serious settlement of solid particles and loss of stability of the slurry, which increases the risk of channeling during cementing. In this work, a polyelectrolyte hydrophobic association composite suspension stabilizer P-AB with good temperature resistance was studied. The results of infrared spectroscopy, thermogravimetric analysis, particle size analysis and cryo-scanning electron microscopy show that: P-AB can form a unique grid structure through electrostatic interaction and hydrophobic association, which helps prevent cement slurry settlement and free water separation ; 1% P-AB aqueous solution can maintain a high viscosity at 40℃-150℃; after adding 0.5%-1% of P-AB to the cement slurry at a high temperature of 200℃, the density difference between the upper and lower sections of the cement stone will be less than 0.02 g/ cm3, the free liquid of the slurry is 0, and Zeta potential analysis shows that the addition of P-AB can improve the dispersion performance of the slurry. This technology is conducive to improving the cementing quality of deep and ultra-deep wells and reducing cementing risks.

  • 1
• Research Progress of Active Components in Crude Oil and Interaction on Influence of Emulsion Stability

  SUN Lin, Ren Zihan

  Abstract: (777) HTML (0) PDF (0.00 ByteKB) (1367)

  Abstract:

  A large amount of emulsion is easily formed in the process of crude oil production due to the existence of active components, including asphaltene, resin, petroleum acid, and wax. Based on the composition and existing state of active components in crude oil, the influence mechanism of each active component on the emulsion stability was described. The interaction between active components and asphaltene with their influence on emulsion stability is summarized. Among the active components of crude oil, these are pointed out asphaltene is the main component of the interfacial film, and suitable resin with asphaltene can strengthen emulsifying effect. The results between carboxylic organic acid and asphaltene are various owing to different relative molecular weights, and the wax can enhance the strength of the interfacial film when they crystallize or interact with asphaltene. Meanwhile, current problems and future development directions are prospected.

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• Preparation and properties of gel dispersion for profile-controlling and flooding by aqueous RAFT polymerization

  YANG Ziteng, ZHANG Peng

  Abstract: (646) HTML (0) PDF (0.00 ByteKB) (1358)

  Abstract:

  Based on reversible addition fragmentation chain transfer (RAFT) aqueous polymerization, the micro/nano-polyacrylamide gel dispersions for profile-controlling and flooding were prepared to solve the problems of complicated preparation processes of common profile-controlling and flooding agents and the need to add organic solvents. A new water-soluble RAFT agent was synthesized, and then polyacrylamide gel dispersions were prepared by using the RAFT agent in water. The effects of reactant ratio, polymerization temperature, polymerization time and solid content on its properties were investigated. The rheological and viscoelastic properties of gel dispersions were tested. The temperature response, salinity responsiveness and pH responsiveness of gel dispersions were characterized. The results showed that the viscosity of gel dispersions decreased with the increase of temperature and decreased with the increase of pH value, but had little effect, and their viscosity was almost not affected by mineralization. Finally, the microstructure and particle size were characterized by atomic force microscope (AFM), scanning electron microscope (SEM) and nano particle analyzer. The results showed that the gel dispersion was irregular globular structure. The micron diameter of the gel dispersions was 0.92 ~ 6.13 μm and the diameter of the nanoparticles was 48 ~ 76 nm, which confirmed that the molecular scale of gel dispersions prepared by RAFT aqueous polymerization was micro/nano scale.

  • 1
• Preparation and performance evaluation of polymer microsphere as drilling fluid filtrate additive

  Liu Yun

  Abstract: (751) HTML (0) PDF (0.00 ByteKB) (1582)

  Abstract:

  As the existing filtrate reducers often have an unsatisfied performance in the high temperature and high salinity environment, a polymer microsphere is synthesized by inverse emulsion polymerization of water-soluble monomers (sodium p-styrene sulfonate, 2-acrylamide-2-methylpropanesulfonic acid and acrylamide) using liquid paraffin as the continuous phase, Span 80 and Tween 60 as emulsifier. Infrared spectroscopy, thermogravimetric analysis, scanning electron microscope and laser particle size analyzer are used to characterize the product. Then the swelling performance, salt resistance, aging performance, temperature resistance and plugging experiments also are studied. It is shown that microspheres display a spherical morphology with a particle size of 2.82-10.26 μm, and begin to decompose at 270 ℃. It is found that the final expansion ratio in deionized water approaches to 500%. In addition, microspheres exhibit a good fluid loss reduction performance in high salinity and high temperature conditions, and have anti-aging property. After plugging experiments, the polymer microspheres are observed in macropore of core slice, where plug performance is achieved by polymer microspheres.

  • 1
• Preparation and analysis of acrylate- methacrylic acid copolymer emulsion reversed demulsifier

  ZHANG Tao

  Abstract: (758) HTML (0) PDF (0.00 ByteKB) (1523)

  Abstract:

  Requirements for sewage treatment chemicals are very high due to the limited sewage treatment equipment and short residence time in offshore oilfield. Thus, it is necessary to develop a high-efficient reversed demulsifier to improve the separation efficient of oil and water. In this work, acrylate-methacrylic acid copolymer emulsion reversed demulsifier (EMASA) was synthesized via emulsion polymerization method by using EA, MAA and SA as precursors. The structure and thermal properties of synthsized copolymer were characterized using FT-IR?, 1HNMR and DSC. The oil removal rates of synthesized copolymers were further investigated based on the water from the offshore oilfield A platform(water type is sodium bicarbonate). Results suggests that the oil removal rate of EMASA was 96.5% under a filling concentration of 30 mg/L, and the value further increased to 98.9% at the assistance of the flocculant,ECHA. Pilot scale test of the property of EMASA was further carried out on platform A. It was found that the OIW at the outlet of the oil system decreased from 255.75mg/L to 197.58mg/L under a EMASA filling concentration of 30mg/L, and the oil removal rate of the oil system increased from 94.89% to 96.05%. The mechanism of the role of EMASA was also clarified based on the results of dynamic light scattering, interfacial tension and expansion modulus.

  • 1
• Experimental investigation of zeolitic imidazolate framework nanoparticles for enhanced oil recovery

  HE Xuan, LIU Yuetian

  Abstract: (682) HTML (0) PDF (0.00 ByteKB) (1274)

  Abstract:

  Nanomaterials have attracted extensive attention in the study of enhanced oil recovery due to their unique physical and chemical properties. However, there are still some shortcomings such as poor dispersion, easy agglomeration and low recovery rate. It is very important to synthesize new nanoparticles and apply them to the research of enhanced oil recovery. In this paper, ZIF-8 nanoparticles were prepared for EOR applications and their microstructures were characterized by X-ray diffraction and field emission scanning electron microscopy. In order to prepare the nanofluids, the nanoparticles were dispersed in brines with different concentrations, which were characterized through analyzing their stability. Then the prepared nanofluids were used to measure the interfacial tension and contact angle between crude oil and water on the surface of sandstones. Finally, the core displacement experiments were carried out. The results show that the average diameter of the prepared ZIF-8 nanoparticles is 65.8nm, and the phase state is single without impurities. When the mass fraction is not higher than 0.03%, the dispersion in water is excellent, and the absolute value of Zeta potential is about 30mV, which has a high stability. After adding 0.03% ZIF-8 nanoparticles in simulated formation water and low salinity water, the interfacial tension values decreased to 4.662 and 3.965mN/m, respectively, which decreased by 75.76% and 73.27% compared with that without adding. The contact angle decreases from 114°, 109° to 78° and 73°, respectively, and the rock surface towards to more water-wet, which is more conducive to the peeling of oil film. Thus, the recovery was increased by 8.25% and 10.71% with 0.03% ZIF-8 nanofluid under the high and low salinity conditions, respectively.

  • 1
• Anti-blocking system in water injection process of low permeability loose sandstone reservoir with high clay

  Liang Yukai, Yu Xiaocong

  Abstract: (538) HTML (0) PDF (0.00 ByteKB) (1209)

  Abstract:

  Aiming at the problem of high injection pressure caused by particle migration blocking the reservoir pore throat in the process of water injection in high clay loose and low permeability sandstone reservoir, a neutral gradient anti plugging system was optimized through laboratory experiments. The low-speed gradient anti plugging system is 0.5% KCl clay stabilizer, and the high-speed gradient anti plugging system is 0.2% KCl + 0.3% organic cationic clay stabilizer. The anti-swelling property of gradient anti plugging system and the changes of core pressure and permeability during displacement were investigated. The results showed that the anti-swelling rate of the system was more than 91%. Compared with the blank production water displacement, at low speed, after being treated by the anti-plugging system, the pressure growth multiple was reduced from 5.41 to 2.03, and the permeability retention rate was increased from 18.49% to 49.15%; At high speed, after being treated by the anti-plugging system, the core permeability gradually recovered. When 8PV was replaced by production water, the permeability retention rate increased from 10.56% to 91.58%, and the pressure growth multiple decreased from 9.47 to 3.28. The plugging prevention system is neutral, which provides a strong support for the advanced green water injection and efficient development of low permeability reservoirs.

  • 1
• Evaluation and application of polymer microsphere / surfactant composite profile control and flooding system

  WU Tianjiang

  Abstract: (1096) HTML (0) PDF (0.00 ByteKB) (1293)

  Abstract:

  According to the characteristics of Changqing Low Permeability Reservoir, polymer microsphere / surfactant composite profile control and oil recovery technology is proposed. The initial particle size of polymer microspheres is generally 50-300nm, and it has hydration expansion characteristics with expansion ratio of 5-10 times. The aggregation characteristics of microspheres during hydration and expansion were observed by SEM, and the particle size distribution was Gaussian normal distribution. The most economical concentration of surfactant is 0.3%. The results show that the viscosity of the mixture increases after adding surfactant to polymer microspheres, and the dispersed phase particles of microspheres shield the interfacial activity and micelle formation ability of surfactant, which results in the decrease of interfacial tension, which is not conducive to surfactant flooding. When the mass concentration of microspheres is greater than 0.4%, the plugging rate is more than 80%. The best injection mode of polymer microspheres and surfactant is slug injection with volume ratio of 1:1. The application effect of this technology in Ansai Oilfield is good, and the cumulative oil increase is 3576t, showing good technical adaptability.

  • 1
• Synthesis and Properties of a MultipStudy on Synthesis and properties of reinforced materials for oil well cement

  Liu Xuepeng

  Abstract: (560) HTML (0) PDF (0.00 ByteKB) (1278)

  Abstract:

  In this paper, a heterogeneous particle was synthesized from diphenylmethane diisocyanate (MDI), polyepoxypropane glycol, silicate aqueous solution and heavy calcium carbonate, which was used to reduce the elastic modulus of oil well cement. The first phase of multiphase particles is a porous continuous phase, and the second phase is basically spherical; In the multiphase particles, the second phase is embedded in the holes of the first phase, and the spherical second phase contains 18 ~ 20% Si element. The experimental results show that the cement stone with multiphase particles has lower elastic modulus than that of neat paste cement stone, but the strength does not decrease; Multiphase particles have little effect on the thickening time and rheology of cement slurry; The spherical structure at the interface of multiphase particles contains a large number of silicon hydroxyl groups, which participate or partially participate in the hydration of cement, forming a permeable structure at the interface to ensure the continuity of cement hydration structure.

  • 1
• Foam Properties and CO₂/N₂ Response Properties of Anionic Surfactant/ Tertiary Amine Compound Foam

  LIU Dong-Mei, SUN Shuang-Qing

  Abstract: (656) HTML (0) PDF (0.00 ByteKB) (1297)

  Abstract:

  In this paper, the foam performance of sodium dodecyl sulfate (SLS), sodium dodecyl sulfonate (SDS), sodium dodecylbenzene sulfonate (SDBS) and N-dodecyl-N, N-dimethyl tertiary amine (C12A) equimolar compound solution were studied through foam experiments, and the influence of inorganic salt and oil relative to the foam performance of the compound system. In addition, for the SLS/C12A compound system and SDS/C12A compound system with better foam performance, CO2 response defoaming and N2 heating recovery re-foaming and defoaming experiments were carried out. The research results show that the SLS/C12A compound system has the best foam stability and strong salt tolerance. The anti-oil effect of the SDS/C12A compound system is remarkable, and the two compound systems both show good CO2 responsiveness and reversibility. According to the change of the solution and the change of surface tension after defoaming, the response mechanism is inferred that the protonated C12A and anionic surfactants are electrostatically attracted to form a complex, which precipitates out of the solution, which reduces the surface activity of the solution and accelerates the breaking of the foam.

  • 1
• Research progress and application prospects of drilling fluid additives in intelligent water-based drilling fluid chemical system

  Shen Haokun

  Abstract: (970) HTML (0) PDF (0.00 ByteKB) (1323)

  Abstract:

  Traditional water-based drilling fluid has some disadvantages, such as tedious process of drilling fluid configuration, poor pertinence and weak adaptive ability. Intelligent water-based drilling fluid has become a new research direction in the field of oilfield chemistry because of its better pertinence and universality, and can greatly reduce the degree of manual intervention. Through literature analysis, the mechanism and research progress of intelligent materials such as intelligent water-based drilling fluid additive in water-based drilling fluid are described. According to the characteristics of different intelligent drilling fluid additives, the feasibility of intelligent materials in water-based drilling fluid is discussed, and the research ideas, methods and application prospects of intelligent drilling fluid additives in intelligent drilling fluid system are prospected.

  • 1
• The Research and Oilfield Trial of Horizontal Well Selective Water Shutoff Agent in Glutenite Oil Reservoir

  Li Yikun

  Abstract: (764) HTML (0) PDF (0.00 ByteKB) (1336)

  Abstract:

  The Kunbei glutenite reservoir has thick layer and strong heterogeneity in plane, interlayer and intralayer. In the early stage of development, the horizontal well production yield decreases and water cut rises rapidly. Horizontal wells are in urgent need of water control. Based on the characteristics of Kunbei reservoir and production, Acrylamide (AM)-2-acrylamido-2-methylpropanesulfonic acid (AMPS)-dimethyldiallylammonium chloride (DMDAAC) terpolymer selective water shutoff agent for horizontal wells was synthesized. The injection performance of water shutoff agent was investigated by rheological mechanics experiment, and the selectivity of water shutoff agent was investigated by core plugging simulation experiment. The core experiment shows that the injection pressure is increased by 6.06 times after water plugging, the water flooding plugging rate is 83.5%, and the oil displacement plugging rate is 20%, which has remarkable oil-water selectivity.On the basis of laboratory experiment and well performance, the oilfield trials of water shutoff for 6 horizontal wells have been carried out in Kunbei Oilfield. The remarkable effect of increasing oil and reducing water has been gained.

  • 1
• Application of New Low-damage and High-performance Micro-foam Drilling Fluid in Coalbed Methane Wells in Eastern Yunnan

  Ma Tengfei, Zhou Yu

  Abstract: (928) HTML (0) PDF (0.00 ByteKB) (1323)

  Abstract:

  The third member of Feixianguan Formation and the first member of Feixianguan Formation in eastern Yunnan are easily unstable formations. In order to protect coal bed reservoirs, new low-damage high-performance micro-foam drilling fluid technology is designed and applied. The developed foaming agent LHPF-1 was compounded with foaming agent BS-12 and tackifier XC, and the response surface optimization experiment was used to analyze the influence of the interaction between the three treatment agents on the foam composite index Fq. On this basis, fluid loss agents and inhibitors are optimized, and the final microfoam drilling fluid formula is determined to be: 0.25%LHPF-1+0.25%BS -12+0.25%XC+1%SPNH+1%NH4HPAN+0.2%KPAM. The research results show that the density of the drilling fluid can be reduced to 0.49g/cm3, the foaming volume can reach 420mL, the half-life of the foam can reach more than 2000min, the thickness of the foam liquid film can reach 50% of the foam size, and the coal core plugging rate and permeability The recovery value is above 90%, and it is resistant to 7% of debris and coal pollution. The drilling fluid was applied on-site in the second opening section of Well LC-C7-2D in the Laochang exploration area in eastern Yunnan. The pure drilling time was 4 days without any complicated downhole accidents. The average caliper expansion rate for the whole section was 5.9% , The fluid loss is less than 5mL.

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• Study on the low-damage slick water fracturing fluid of Baikouquan Formation in Mahu 1# well area

  ZHANG Ying, YU Weichu

  Abstract: (902) HTML (0) PDF (0.00 ByteKB) (1274)

  Abstract:

  Baikouquan formation in Mahu 1# well area is a typical tight oil reservoir with low porosity and low permeability, which large-scale hydraulic fracturing is need to increase production. However, there are three major problems. First, the fracturing fluid has poor drag reduction effect and is harmful to the reservoir. Second, water resources are scarce and oil field sewage treatment is difficult. Third, the recovery rate needs to be improved because of the distribution of residual oil between the joints. So, the JHFR drag reduction agent was synthesized which is low-damage. And then, JH slick water fracturing fluid with low damage was constructed. JH mainly composed of 0.1% JHFR drag reduction agent and 0.2% JHFR multifunctional additives. The fluid is characterized by instant dissolution (15 s), high efficiency drag reduction (76.9%), low oil-water interfacial tension (0.89 mN/m), and good anti-swelling effect (CST ratio 0.92)., and other characteristic. The system has good compatibility with formation water and backflow fluid in the Mahu 1# well area, and the damage degree to core permeability is low. So, it is suitable for large-scale continuous fracturing in the Mahu 1# well area.

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• Study and Field Application of Organic Boron/Zirconium Composite Linear Gel Fracturing FluidWAN Qingshan_^1*, BAI Lei_¹,LI Bin_²,CHEN Liyan_¹,ZHAKE Jian_¹

  Wan Qingshan

  Abstract: (779) HTML (0) PDF (0.00 ByteKB) (1279)

  Abstract:

  Based on the formation principle of partially hydrolyzed polyacrylamide (HPAM) and polyhydroxyl alcohol weak gel, the crosslinking agent FHBZ-1 was used to prepare the crosslinking gel with HPAM and polyhydroxyl alcohol, and it was used as the fracturing fluid of LG-2 composite linear gel. Zirconium crosslinking agent was prepared by mass ratio of Zirconium chloride, lactic acid, propyl alcohol, triethanolamine of 6:5:1:24 in 75℃ water bath for 2h. Boron cross-linking agent was prepared by mass ratio of Borax, mannitol, water/glycerol (volume ratio 3:1) Mixed solvent, NaOH of 18:16:6:2, pH value: about 10, reaction temperature: 80℃, reaction time 5h.The organic boron crosslinking agent and the organic zirconium crosslinking agent were mixed according to the volume ratio of 1:2 to form FHBZ-1.The crosslinking, temperature resistance and shear resistance of LG-2 linear gel fracturing fluid system were evaluated respectively.Experiment from LG - 2 linear gel fracturing fluid optimization ratio of 0.3% (wt) HPAM + 0.5% (wt) CPA - 1 + 1.2 (v) % FHBZ - 1 + 0.05% (v) ZP + 0.3% + 0.05% APS NW (v).The final viscosity of 448mPa?s was obtained by shear at a constant speed of 170s^-1 for 90min at 130℃, indicating its good temperature and shear resistance.The performance of LG-2 linear glue fracturing fluid was evaluated at 60 and 90℃. The viscosity of LG-2 linear glue fracturing fluid was small, and the amount of residue was low, which was about 16mg/L and 12mg/L, respectively.Field test of WY-8 shale gas well verified that LG-2 linear glue fracturing fluid system has excellent performance of seam making and sand carrying.

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• Research on Mechanism of Pickering Microemulsion Control Swelling of Clay in Heavy Oil Reservoir

  Guo MIngzhe

  Abstract: (766) HTML (0) PDF (0.00 ByteKB) (1317)

  Abstract:

  Inhibition of clay expansion is a premise of effective thermal recovery in water sensitive heavy oil reservoir, however, a quantitative description of mechanism that stabilizer inhibits clay expansion, which is remaining unclear. First, a Pickering microemulsion applied to control clay swelling was proposed, besides mechanism of expansion inhibition Pickering microemulsion was analyzed by combination of Fick"s law and Langmuir theory of adsorption. Then, effect of Pickering microemulsion formed by the compounded mixtures of hydrophobic nano SiO2 and lauryl three methyl ammonium bromide (DTAB) on water surface tension was tested, and the suppression bentonite’s swelling rate of the Pickering microemulsion was also measured, which obtained optimum formulation. Finally, the dynamic anti-swelling effect of the Pickering microemulsion was studied by slug displacement experiments through best formula. The quantitative analysis shows that it is feasible to prevent clay swelling by surface adsorption. When the ratio of nano-SiO2 to DTAB is 1:2 and the concentration is 0.6wt%, the best inhibition effect of bentonite was obtained. The best slug injection volume is 0.2PV in test. with unceasingly increasing microemulsion injection volume, the anti-swelling effect was more obvious. But the rate of increase of water cut also was accelerated, which indicated that the clay swelling should be properly controlled in heavy oil reservoirs with high permeability.

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• water-soluble resin-based cementing fluid system

  HE Yingzhuang, YAN Siming

  Abstract: (540) HTML (0) PDF (0.00 ByteKB) (1438)

  Abstract:

  In view of the problems of gas channeling and wellhead pressure caused by high pressure and fracturing in the development of oil and gas fields, water-soluble resin was used as the main cementitious materials and a resin-based cementing fluid system at low and medium temperature was prepared. The engineering performance, anti-channeling ability, mechanical property, temperature resistance and curing kinetics of the system were studied. The results show that the density of the resin system can be adjusted to 1.20~1.80g/cm³ through the combination of weighting agent and suspending agent, and it has good flowing ability. The thickening time can be adjusted from 60 to 410 min by changing the dosage of curing agent and accelerator between 60℃ and 90℃. When the displacement efficiency is 91.5%, the consolidation strength of cured resin is 3.01 MPa, the interface breakthrough pressure is more than 12 MPa, which is much higher than that of conventional cement stone under similar displacement efficiency. The compressive strength of cured resin is above 50MPa after curing at 90℃ for 24h, and the elastic recovery rate is more than 85% after six cycles of alternating stress loading, which is better than that of ordinary set cement. The TG analysis demonstrates that initial decomposition temperature of cured resin is 398℃, which indicates that the resin-based cementing fluid has good temperature resistance. The curing kinetics equations of S-HR/CA-1and S-HR/DCY systems, and the relationship between curing degree and curing time was determined. The resin cementing fluid has consolidation strength and strong deformation recovery ability at the cementing interface, which is conducive to ensuring the long-term integrity and sealing performance of cementing material, and preventing fluid channeling of oil and gas wells. The study of curing kinetics provides a theoretical reference for the research and application of this kind of resin working fluid system.

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• Demulsification Mechanism of quartz sand on heavy oil emulsion

  ZHANG Dianchen, ZHANG Shijian

  Abstract: (628) HTML (0) PDF (0.00 ByteKB) (1329)

  Abstract:

  Because the heavy oil emulsion is opaque and it is impossible to intuitively understand the influence of sand particles on the stability of heavy oil emulsions, some scholars have detected the asphaltenes adsorbed on the surface of mineral particles by Fourier transform infrared spectroscopy. It is speculated that these particles destroy the strength of oil/water interfacial film due to the adsorption of asphaltenes on the oil/water interfacial film and promote the aggregation of water droplets,Sso as to realize demulsification and stratification of heavy oil emulsion.SHowever, this understanding cannot explain some phenomena in our experiment. In this paper, experiments such as bottle experiment, rheology test and wettability test are carried out, and the influence mechanism of quartz sand on the stability of heavy oil emulsion is obtained: when the sand particle size is small and the water droplet particle size is large, the phenomenon of water droplets completely wetting and wrapping the sand particles will occur, the proportion of water droplets wrapping the sand particles will increase, and the settlement speed will accelerate,SThis is the main reason for the demulsification and stratification of heavy oil emulsion by sand, and this understanding is also verified by the sedimentation experiment of sand in white oil.

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• Synthesis and evaluation of a new small molecular clay stabilizer ZWS-1with high temperature resistant

  SHEN Huibing, WU Pingping

  Abstract: (837) HTML (0) PDF (0.00 ByteKB) (1349)

  Abstract:

  In view of the problems such as poor washing resistance of inorganic salt clay stabilizer, easy adsorption and blockage of pore channel and poor temperature resistance of polymer clay stabilizer, it is urgent to develop a new type of small molecule clay stabilizer for high temperature and low permeability reservoir. In this work, high temperature resistant clay stabilizer ZWS-1 was synthesized with trimethylamine and γ-chloropropyltriethoxysilane. The optimized weight concentration of ZWS-1 applied for clay stabilization was 1.5%. A synergistic effect was observed on 5% ZWS-1 and 4% KCl, which exhibited a decrement of clay swelling of 98.3%, and the washing resistance of 91.4% at 150 ℃. The characterization results indicate that ZWS-1 leads to the agglomeration of clay particles and increase the stability of clay. Fourier transform infrared spectroscopy (FTIR) results reveal that ZWS-1 reacts with hydroxyl groups of the clay surface, which indicates that the presence of chemical bond between ZWS-1 and clay minerals.

  • 1
• Research on Imbibition of Surfactant to Improve the Production Characteristics of Crude Oil in Matrix-fracture Dual Media

  WANG Xingkun, DAI Caili

  Abstract: (890) HTML (0) PDF (0.00 ByteKB) (1452)

  Abstract:

  Surfactant imbibition is an important means to improve the production of tight oil matrix crude oil and the characteristics of surfactant imbibition in the tight oil matrix-fracture model to improve crude oil production was studied in this paper. First, 0.05 wt% of ASB is preferred as a surfactant for imbibition by spontaneous imbibition, measuring interfacial tension, and wettability. Furthermore, through the matrix-fracture core model and the microfluidic model, the effects of the fracture tortuosity and the velocity in the fracture on the dynamic imbibition of the near-fracture matrix to improve the production characteristics of crude oil were studied respectively. The results show that the degree of crude oil recovery by dynamic imbibition of the near-fracture matrix increases with the increase in the tortuosity of the model, that is, the higher the fracture complexity, the higher the degree of dynamic imbibition recovery; the faster the flow velocity in the fracture, the oil-water interface in the capillary the faster the migration rate, that is, the faster the imbibition rate, and the migration rate of the oil-water interface and the flow velocity in the fracture conform to the law of quadratic function as a whole. Also besides, the effects of the action depth and concentration of surfactant on the spontaneous imbibition of the deep matrix to improve the production characteristics of crude oil were studied through static imbibition experiments. The results show that the deeper the surfactant action depth, the lower production of crude oil per unit volume. When the surfactant concentration is high, the variation law of the degree of spontaneous imbibition production is consistent with the interfacial tension as the main control parameter of the capillary force is the interfacial tension. When the surfactant concentration is low, the main controlling parameter of the capillary force is the wettability of the rock surface. At this time, the variation law of the degree of spontaneous imbibition and production is opposite to the interfacial tension.

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• Efficient preparation of nano starch particles and its effect on the performance of drilling fluid

  Ma Peng, Zhang Lei

  Abstract: (850) HTML (0) PDF (0.00 ByteKB) (1592)

  Abstract:

  In order to meet the requirements of environmental protection and efficient drilling of unconventional shale reservoirs, it is necessary to develop a new type of drilling fluid system with excellent performance and environmental friendliness. In this paper, ultrasonic treatment and precipitation method are combined to solve the problem. First, ultrasonic treatment is used to reduce the viscosity of starch solution with a high concentration of 5%. Thus, the precipitation method is used to prepare nano-starch particles under the condition of high concentration starch solution. After preparation by the method, the average size of the nano starch particles is as small as 30nm, and the particle size is mainly concentrated in 20-50nm with a relatively uniform distribution. The salt resistance of the nano starch particles is 20g/L NaCl at 150°C. After adding 1.0% nano starch particles to the base slurry, the apparent viscosity, plastic viscosity, dynamic shear force and fluid loss are 22.0 mPa.s, 14.5 mPa.s, 11.5 Pa and 9.3 mL, respectively. After aged at 150℃, the apparent viscosity, plastic viscosity, dynamic shear force and fluid loss after 16 hours are 21.1 mPa.s, 14.0 mPa.s, 10.8 Pa and 10.0 mL, respectively. More importantly, nano-starch particles and bentonite can form a network structure, which can increase the apparent viscosity, plastic viscosity, and shearing force of the drilling fluid, and decrease fluid loss, and it can still maintain excellent performance after aging under high temperature. The combination of ultrasonic treatment and sedimentation method is easy to be operated, low cost, easy to be promoted and applied. The formed technology can provide an important technical support for the development of a new type of nano-drilling fluid system.

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• Research on the influence of complex fluids in oil fields on the performance of scale inhibitors

  FENG Keting, YUAN Huiying, YANG Le, WANG Yisha, CHEN Bin, TIAN Yuxin, LV Feng

  Abstract: (10) HTML (0) PDF (0.00 ByteKB) (0)

  Abstract:

  In the process of oilfield development and production process, scale inhibitors are widely used to mitigate scaling issues in reservoirs, wellbores, and pipelines. However, the mechanisms of scale inhibitors against scaling ions such as Ca2? and Mg2? in high-salinity fluids remain unclear. Additionally, the coupling effects among field-applied scale inhibitors, biocides, and corrosion inhibitors are still unexplored, which hinders the efficient and scientific application of chemical agents. This study innovatively establishes a dynamic laser turbidity testing platform using a non-invasive device to accurately simulate rapid batch testing of scale inhibitors under oxygen-free, high-temperature, and flowing conditions in reservoirs. By comprehensively considering factors such as complex ions, scale inhibitors, and their interactions, the study develops predictive models for dynamic scaling and scale inhibition of MgxCa1-xCO3 and BaxSr1-xSO4 in complex ion environments. It investigates the interactions between additives and scale inhibitors, clarifying the synergistic and antagonistic effects of demulsifiers, corrosion inhibitors, and biocides on scale inhibitors. These findings aim to provide guidance for precise selection of high-efficiency synergistic chemical systems and cost-effective improvements in chemical protection technologies.

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• Advances on emulsion stabilization and transfer technology for water control in oilfield

  Shen Linghong, LU Yuanyuan, SONG Zhengcong, KANG Bohan, YANG Yuqi, YIN Taiheng

  Abstract: (11) HTML (0) PDF (0.00 ByteKB) (0)

  Abstract:

  In the high water cut development stage of oilfields, selective water shutoff technology is crucial for enhancing oil recovery. Emulsion-based water shutoff technology has emerged as a research and application hotspot due to its advantage of selective plugging. This paper systematically reviews the mechanisms of selective water shutoff using emulsions, including core processes such as viscosity increase and mobility control, physical plugging and Jamin effect, and rock wettability alteration. The influences of various factors on emulsion stability, such as emulsifier type, pH value, temperature, salinity, and crude oil composition, are analyzed in detail. Traditional emulsion-based water shutoff systems (active heavy oil-based and emulsion-based) and their stabilization technologies are summarized and compared. Furthermore, novel heavy oil emulsion phase inversion water shutoff systems are introduced, and the phase inversion mechanisms and technical progress based on salinity and pH control are discussed.

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• Preparation and Performance Evaluation of a Pre-Assembled Core–Shell Phase-Change Profile Control Agent for Fractured Low-Permeability Reservoirs

  Wang Qianlong, Zheng Lijun, Zhu Jiaji, Zhang Ning

  Abstract: (8) HTML (0) PDF (0.00 ByteKB) (0)

  Abstract:

  To address the problem of microfracture development, limited sweep efficiency of water flooding, and the tendency to form dominant flow channels after long-term water injection in the fractured low-permeability reservoir of the Chang 6 formation in Block W of Wuqi Oilfield—which makes it difficult for conventional plugging agents to achieve effective deep profile control—a pre-assembled core–shell phase-change profile control agent (TSAD) was developed. Dynamic light scattering particle size analyzer, rotational viscometer, microfracture piston extrusion device, and core flooding experimental setup were used to systematically study the particle size distribution, phase-change characteristics, plugging strength, and water-plugging/oil-displacement performance of the TSAD agent. The results showed that the TSAD droplets had a particle size distribution of 20–300 nm, exhibiting good injectivity. The phase-change time could be controlled within 5–12 days, making deep profile control feasible. Plugging strength increased with concentration; at a 20% concentration, the breakthrough pressure reached 6.72 MPa and the stable pressure reached 6.14 MPa, meeting the strength requirements. The phase-change process was unaffected by the pH and salinity of the on-site water. Core flooding experiments showed that, under injection of 0.3 PV and a 1% mass concentration TSAD system, the plugging rate of high-permeability cores reached 80.69%, while that of low-permeability cores was only 3.1%, and the oil recovery efficiency in low-permeability channels improved by 14.08%, confirming the agent"s effectiveness in plugging fracture channels and enhancing oil recovery. A field pilot test was carried out in well group X-XX of the Chang 6 reservoir in Block W of Wuqi Oilfield. The comprehensive water cut of the well group dropped by 25.85%, and the daily oil production increased from 5.84 t to 7.33 t, achieving a daily oil increment of 1.49 t. This system demonstrates excellent deep profile control performance in fractured low-permeability reservoirs and provides a new idea and effective technical means for water control and enhanced oil recovery.

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• Adaptability of Backflowed Wastewater Storage Layers in High-Salinity Oilfields and Improvement Measures

  MENG Xinzhi, CAO Weijia, LU Xiangguo, LIU Zilong, XIE Kun, WANG Yongjiang, YIN Xianpei

  Abstract: (17) HTML (0) PDF (0.00 ByteKB) (0)

  Abstract:

  At present, the major oil fields in the eastern part of China are in the stage of high-salinity exploitation. The problems of inefficient and ineffective circulation are very serious. The large amount of produced liquid treatment leads to a sharp increase in production and operation costs. The main technical indicators of the injected wastewater often fail to meet the industry requirements. The residual polymers, crude oil and suspended solid particles in the wastewater are bound to cause blockage and damage to the low-permeability areas of the reservoir. In order to clarify the limit of the reservoir permeability for wastewater injection and to construct improved methods for the adaptability of wastewater reservoirs, this paper intends to use physical chemistry, polymer chemistry and reservoir engineering as theoretical guidance, and employ technical means such as instrument detection, chemical analysis and physical simulation. Taking the injected wastewater and reservoir properties of the XSG oilfield as the research objects, it will conduct experimental research on the reservoir adaptability and improvement measures of wastewater injection in high-salinity oil fields. The results show that the oil content, suspended matter content and median particle size of the injected wastewater in the three under-injected wells are far beyond the industry water quality standards. Their retention and blockage in the pore spaces of the reservoir rock cores are the main reasons for the under-injection of water wells. The minimum reservoir permeability of well 1# after injecting wastewater is slightly 16910-3m2, well 3# are slightly 10310-3m2. The optimal mixing ratio of clear water can increase the Zeta potential value of suspended particles in the mixed water., the stability of the suspended matter particles enhances, the particle size of the suspended matter and the compatibility with the pore spaces of the rock cores improve, and the degree of reservoir blockage damage is reduced. From a technical and economic perspective, it is recommended that the ratio of wastewater to clear water for well 1# and well 3# is 4:6 and 6:4.

  • 1
• Experimental Evaluation of Dimethyl Ether Assisted CO2 Flooding for Enhancing the Recovery Rate of Shale with Three Types of Pore Structures

  LU Xuejiao

  Abstract: (13) HTML (0) PDF (0.00 ByteKB) (0)

  Abstract:

  To address the challenges of high difficulty in achieving miscibility and low recovery rate in CO2 flooding of shale oil, a technology of DME-assisted CO2 flooding to enhance shale oil recovery rate was proposed. Based on the understanding of the effects of DME on the interfacial tension, viscosity and miscibility pressure between CO2 and crude oil, three types of shale with different pore structures from the Huahai Depression in the Jiuquan Basin were selected to conduct core experiments of CO2 flooding and DME-assisted CO2 flooding. Low-field core nuclear magnetic resonance testing technology was used to study the oil displacement characteristics of CO2 flooding and DME + CO2 flooding in shales with different pore structures, quantitatively characterize the degree of crude oil mobilization in microscopic pores, and evaluate the potential of DME + CO2 flooding to enhance shale oil recovery rate. The experimental results show that the pore structures of the target reservoir shales can be classified into types I, II and III, with the pore structures and seepage capabilities getting worse in sequence and the proportion of nano-pores increasing. DME significantly reduces the viscosity, interfacial tension and miscibility pressure of crude oil by increasing the solubility of CO2 in crude oil, with the optimal DME content being 15%. Compared with CO2 flooding, DME + CO2 flooding can significantly increase the recovery degree of small and large pores in the three types of shales. With the increase of injection pressure, DME + CO2 can achieve miscibility at a lower injection pressure, further significantly increasing the recovery degree of small pores, and the contribution of small pores to the recovery rate increases. Among them, the recovery rate increase of types II and III shales is greater than that of type I. The recovery rates of CO2 flooding for the three types of shales from high to low are II, I and III, while the recovery rates of DME + CO2 flooding from high to low are II, III and I. This indicates that DME + CO2 flooding not only significantly increases the recovery rate but also stimulates the development potential of type III shales with poor pore structures. The research results provide a new method for enhancing the development of shale oil through CO2 injection.

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• Preparation and Performance Evaluation of Modified Nano-Graphene Oxide Asphaltene Inhibitor

  Liu Li, Zhao Shuaishuai, Liu Jinxin, Xiao Chuanmin, Li Zhihao, Xing Mengyi

  Abstract: (10) HTML (0) PDF (0.00 ByteKB) (0)

  Abstract:

  To address the issues of reservoir pore-throat blockage and permeability decline caused by asphaltene deposition during CO2 flooding in low-permeability reservoirs, this study proposes a novel technical approach utilizing nanomaterials to inhibit asphaltene deposition. Using graphene oxide (GO), aniline, and decylamine monomers as raw materials, modified nano-graphene oxide (GO-BD) was prepared via covalent grafting. Systematic asphaltene dispersion experiments and online CO? flooding experiments based on low-field nuclear magnetic resonance (NMR) were conducted to evaluate its effectiveness in inhibiting asphaltene deposition. The research results show that: The GO-BD prepared after modification of GO exhibits good hydrophobicity; GO-BD possesses excellent performance in inhibiting asphaltene deposition, significantly delaying the onset point of asphaltene precipitation and reducing its aggregate size. At a GO-BD concentration of 25 mg/L, the asphaltene precipitation point of the oil sample increased from 42.03% to 58.27%, and the asphaltene aggregate particle size decreased from 1297 nm to 498 nm; During the CO2 flooding process, compared to injecting pure CO2, adding a GO-BD inhibitor with a mass fraction of 0.8% to the crude oil reduced the core permeability damage rate by 69.8%, decreased the pore blockage rate by 7% to 10%, and increased oil recovery by more than 10%. The research results provide reference and guidance for inhibiting asphaltene deposition during CO2 displacement processes using nanofluid materials.

  • 1
• Adaptability Study of High-Temperature and High-Salinity Resistant Foam in Fractured-Vuggy Weathering Crust Reservoirs

  SONG Zhengcong, HAN Guoqing, ZHAO Yajie

  Abstract: (21) HTML (0) PDF (0.00 ByteKB) (0)

  Abstract:

  Fractured-vuggy carbonate reservoirs in Tahe Oilfield pose significant challenges for enhanced oil recovery during mid-to-late development, due to their high-temperature, high-salinity conditions and complex storage structures. To address this, an adaptability assessment of foam-assisted gas flooding technology resistant to such harsh conditions was carried out. The study encompassed three main aspects: foam system screening and performance evaluation, physical model displacement experiments, and field pilot testing. Results show that the selected TKQP-3 foam performs excellently at a mass concentration of 0.5%. Under high-temperature and high-pressure conditions, it maintains a foam volume expansion factor above 4, with a drainage half-life of approximately 30 minutes. After rock cuttings adsorption, the foam volume retention remains at 97%, and the resistance factor exceeds 40 at a gas-liquid ratio of 1.5:1. Laboratory simulations confirmed that the system enhances sweep efficiency through mechanisms including flow diversion, improved gas-oil mobility ratio, synergistic foam-gas-water interaction, and reduced interfacial tension, contributing to an average EOR increase of over 10%. Field pilot tests further validated its effectiveness, with the A71 well group achieving a cumulative incremental oil production of 10,373 tons. Overall, foam-assisted gas flooding demonstrates strong adaptability and considerable potential for EOR in Tahe fractured-vuggy reservoirs.

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• (1. School of Biology and Agricultural Science and Technology, Zunyi Normal University, Zunyi, Guizhou, 563006, China;2. No.2 Oil Production Plant, PetroChina Changqing Oilfield Company, Qingyang, Gansu, 745100, China;

  ZHANG Xingchun, zhangzheng, wu ke, yanqiangwei, yuanbin, jaingxunaxuna

  Abstract: (24) HTML (0) PDF (0.00 ByteKB) (0)

  Abstract:

  A novel amide sulfonate zwitterionic surfactant (LECN) was synthesized via a two-step reaction using lauric acid, N,N-dimethylethylenediamine, and sodium 3-chloro-2-hydroxypropanesulfonate as raw materials, with the optimal molar ratio of raw materials optimized to 1:1.1:1.1. The critical micelle concentration (CMC) of LECN is 0.05 g·L-1, with a corresponding surface tension of 28.2 mN·m-1. At a concentration of 0.1 g·L-1, it can reduce the cyclohexane-water interfacial tension to an ultra-low level of 0.045 mN·m-1. Its foaming performance (foaming volume of 670 mL, half-life of 1900 s), emulsifying stability (water separation rate of 35.5% within 70 minutes), and temperature and salt resistance (surface tension variation range ≤ 4.7 mN·m-1 at 120℃ and salinity of 120 g·L-1) are all significantly superior to those of reference samples CAB, SDS, and Triton X-10. The synthesis route of LECN is characterized by easily available raw materials, mild reaction conditions, simple operation, and potential for industrial application, providing a new strategy for the development of high-performance zwitterionic surfactants and is expected to promote its application in fields such as petroleum exploitation and daily chemical industry.

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• A Testing Method for the Content of Cross-linked Network Structure of Viscoelastic Particle Oil Displacement Agent

  Pan Binlin, Chen Xiaoyan, Liuyu, Jiang Zuming, Song Xinyue, Shijing

  Abstract: (21) HTML (0) PDF (0.00 ByteKB) (0)

  Abstract:

  In view of the lack of characterization methods for the crosslinked network structure content of viscoelastic particle oil displacement agent products (PPG and B-PPG) at present, the test on the crushing conditions of gel particles in viscoelastic particle oil displacement agent solution confirmed that the crushing extraction process of gel particles was divided into two stages: crushing and trimming, and the best crushing conditions were selected; By conducting interference removal tests on linear structures in viscoelastic particle oil displacement agent solutions, aluminum nitrate was selected as the complexing agent. It was confirmed that with the increase of aluminum nitrate dosage, a three-stage complexation process occurred, and the optimal complexation conditions for completely removing linear structure interference were obtained. Based on the above research, the final testing process for network structure content in viscoelastic particle oil displacement agent samples was obtained. Using the established testing process, the content of cross-linked network structure in actual viscoelastic particle oil displacement agent samples was tested. The results showed that the cross-linked network structure content of B-PPG was about 86%, and that of PPG was about 25%. B-PPG had more cross-linked network structures than PPG.

  • 1
• Mechanisms of Permeability Enhancement and Fluid Channeling in Hydraulic Fractures via the Dimensionless Liquid Productivity Index during Water Injection

  LIU Miaomiao, HUANG Shijun, ZHAO Fenglan, LIU Yue, WANG Jiaxiang, XIAO Hongrui

  Abstract: (29) HTML (0) PDF (0.00 ByteKB) (0)

  Abstract:

  Low-permeability oil reservoirs typically require fracturing technology for production enhancement. However, the artificial fractures created by fracturing exacerbate reservoir heterogeneity, leading to issues such as injected water channeling and rapid water breakthrough in production wells. This results in inefficient oil mobilization and low recovery rates. To investigate the impact of fractures on water-flooding development in low-permeability oil reservoirs, a physical simulation experiment was conducted. The relative permeability curves of oil and water were measured using cores with different permeabilities and fracture lengths. Based on these curves, the dimensionless liquid productivity index and dimensionless oil productivity index were calculated. A chart illustrating the influence of reservoir physical properties and fracture length on liquid and oil productivity was established, and the distribution patterns of remaining oil after water flooding were revealed. The results indicate that fractures have a dual effect: enhancing permeability and causing channeling. In low-permeability reservoirs with poor physical properties, fractures significantly improve flow capacity and promote the movement of oil and water. However, they also intensify reservoir heterogeneity (as indicated by an increase in the fracture-to-matrix permeability ratio, Kf/Km), making injected water prone to channeling along the fractures. This leads to a sharp rise in the dimensionless liquid productivity index, with remaining oil primarily concentrated in the central part of the core and on both sides of the fracture. For reservoirs with the same physical properties, an increase in fracture length expands the controlled range, enhances oil displacement efficiency, and improves recovery. However, it also further intensifies reservoir heterogeneity and channeling, causing premature breakthrough of injected water. This results in a rapid increase in water cut and a swift rise in the dimensionless liquid productivity index, with remaining oil accumulating near the fracture at the production end of the core. This study provides theoretical and technical support for optimizing fracturing development and designing water-flooding strategies in low-permeability oil reservoirs.

  • 1
• Study on the Shear Viscosity Recovery Performance of Ultrahigh Molecular Weight Zwitterionic Polymer Aqueous Solution

  YANG Haien, ZENG Lixiang, SONG Mingming, LIU Yunlong, FENG Xiaoya, LIU Yan, WU Baoqiang, CAO Lu, SHI Mengquan

  Abstract: (25) HTML (0) PDF (0.00 ByteKB) (0)

  Abstract:

  In response to the problem of shear viscosity loss of polymers in porous media of low-permeability reservoirs, 21.38 million ultra-high molecular weight zwitterionic polymers were prepared by copolymerization of acrylamide (AM), 2-acrylamide-2-methylpropanesulfonic acid (AMPS), dimethyl diallyl ammonium chloride (DMDAAC), supplemented by a small amount of acrylic acid (AA), and post-hydrolysis, cationic and anionic groups were simultaneously introduced into the polymer chain. The molecular structure of target quaternary polymer was evidenced by FT-IR and 1H-NMR. Using a self-built constant flow capillary shear device, the factors affecting the shear viscosity recovery performance were explored from the aspects of polymer composition and injection rate. The viscosity recovery process of polymer after shear was characterized by DLS, TEM, and rheometer. Results show that the reversible attractive interaction between cations and anions can enhance the initial viscosity of the polymer and give the polymer viscoelastic properties, after thinning through capillary shear, the ionic bond between polymers can be recovered by itself, so that the viscosity can be quickly recovered. The polymer with the best overall effect obtained by using 20% AMPS, 0.02% ammonium formate, 0.5% DMDAAC, and 25% degree of hydrolysis, its viscosity can be recovered to more than 80% within one hour in the shear rate range of 4500 s-1. The excellent viscosity self-healing properties of shear and the resistance to formation adsorption make it have great application potential in the field of deep profile control and water plugging of low-permeability oil reservoirs.

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• The impact of ultrafine diabase powder on the performances of oil well cement in well cementing under high temperature conditions

  HE Fuyao, YAN Weifeng, WANG Xijie, YUAN Xiujin

  Abstract: (19) HTML (0) PDF (0.00 ByteKB) (0)

  Abstract:

  The performance of cementing cement stone is prone to decline in high-temperature and complex environments, and the environment containing acidic gases has a significant negative impact on the sealing ability of the cement sheath. In order to improve the performance of cementing slurry at high temperatures, this paper evaluates the effect of ultrafine diabase powder dosage on the performance of cementing slurry. The microstructure of cement paste containing diabase powder was analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results showed that compared with blank cement slurry, the thickening time of cement slurry containing diabase powder was slightly shortened, and the permeability and water loss were reduced. After 30 days of curing, the mechanical properties of cement paste containing 10% diabase powder were relatively more stable. At high temperatures, the compressive strength increased with the extension of curing time, and the compressive strength increased by 46.54% compared to the blank sample. After 14 days of corrosion in a high-temperature CO2 environment,, the corrosion depth of cement paste containing 10% diabase powder decreased by 51.57% compared to blank cement paste. After adding diabase powder into the cementing slurry, the hydration products of the cement stone were optimized. At high temperatures, the microstructure of the cement stone was dense, ensuring good mechanical properties and strong CO2-corrosion resistance.

  • 1
• Performance Optimization and Descaling Mechanism of Composite Iron Scale/Calcium Carbonate Scale Remover

  LI Xin, ZHAO Mingwei, DING Qinfang, ZHANG Huan, MA Zhenfeng

  Abstract: (26) HTML (0) PDF (0.00 ByteKB) (0)

  Abstract:

  Scale buildup is one of the primary causes of reduced production in oil and gas fields. In response to challenges faced by a high-salinity oilfield, including complex scale composition, unsatisfactory conventional descaling effectiveness, and severe corrosion during the descaling process, this study systematically conducted comprehensive quantitative component analysis, descaling efficiency evaluation, chemical compatibility testing, and corrosion assessment based on actual field scale samples. Accordingly, an efficient and safe descaling strategy was proposed. The results showed that the collected scale samples had high levels of Fe and Ca elements, with the scale composition consisting of 16.33% organic matter and 83.67% inorganic matter. The insoluble organic matter included resin and asphalt, while the inorganic matter comprised 46.02% magnetite, 37.65% calcite, and dolomite. When using the multifunctional anionic scale remover Q Series-at a ratio of 7.5% asphalt gum scale remover + 10% carbonate scale remover + 10% iron oxide scale remover, the descaling effect was excellent, with a descaling rate of 97.58% under conditions of 78°C and 24 hours. The descaling system demonstrated stable performance in high-salinity environments. Even when the NaCl concentration varied within the range of 180,000 to 240,000 mg·L-1, the decrease in descaling efficiency remained within 5% compared to that in a zero-salinity condition, indicating excellent compatibility with formation water. The corrosion potential of the descaling system on well casings was also studied. By adding oleic acid imidazoline quaternary ammonium salt corrosion inhibitors at a concentration of 0.6%, the corrosion rate was reduced to 0.44 mm·a-1, below industry standards. Therefore, this descaling system not only effectively removes mixed scale deposits and reduces the risk of blockages but also minimizes corrosion on equipment, thereby lowering operational costs.

  • 1
• Study on Low-Concentration SDBS/AEO-7 Compound System Synergistic CO? Flooding Enhancement in Medium-Permeability High Water-Cut Sandstone Reservoirs

  XUE Jinli, WANG LI, FENG Zijuan, XU Peng, LI Qingming

  Abstract: (19) HTML (0) PDF (0.00 ByteKB) (0)

  Abstract:

  With the growth of petroleum energy demand and the depletion of conventional oil and gas resources, the major oilfields in China have entered the high water-cut development stage. The oil displacement efficiency of CO2flooding technology is limited due to issues such as the significant gas-oil mobility ratio and high interfacial tension; meanwhile, traditional high-concentration surfactants have drawbacks including high cost and poor compatibility. To address these problems, this study proposes a 0.15 wt% SDBS/AEO-7 (1:1) low-concentration compound system, and systematically investigates its synergistic enhancement mechanism for CO2flooding through contact angle, interfacial tension, viscosity, and slim-tube displacement experiments.The results show that, relying on the electrostatic-hydrogen bond synergistic mechanism, this system achieves an ultra-low interfacial tension of 0.0015 mN/m, with a salinity tolerance of up to 80 g/L. The increase in interfacial tension is less than 15% at 100℃. For medium-permeability cores (240 mD, pore throat 5–10 μm), the oil displacement efficiency reaches 90.8%, which is 11% higher than that of single CO2 flooding. This system breaks through the bottleneck of traditional CO2flooding and provides a new path for increasing production in high water-cut reservoirs.

  • 1
• Construction and performance evaluation of anionic surfactant /nonionic surfactant / polymer viscosity reduction composite flooding system

  LIAO Jian, HUANG Zhixue, ZHANG Fumin, WANG Hongbo, YU Zhenye, WANG Yefei

  Abstract: (40) HTML (0) PDF (0.00 ByteKB) (0)

  Abstract:

  In order to solve the problems of high viscosity and poor fluidity of heavy oil in Xinjiang Oilfield, an anionic / nonionic surfactant / polymer viscosity reduction composite flooding system (SP-L) is constructed in this paper. Taking viscosity reduction rate and interfacial tension as evaluation indexes, the optimum ratio of the system is determined by single factor experiment to be 0.25wt % surfactant ( molar ratio of AEO-9 to KPS 1 : 1 ) and 0.1wt % HPAM. The results show that at 53 °C, the oil-water interfacial tension between 0.25wt % ( AEO-9 / KPS ) and heavy oil is 1.1×10-2mN / m, and the viscosity reduction rate of heavy oil is 98.8 %. The O / W emulsion formed by SP-L and heavy oil has an average particle size of 13 μm and a distribution range of 4-30 μm, and can convert oil-wet reservoirs into water-wet (contact angle decreased from 115°to 20.3°). Compare with the commercially available JN-1 viscosity reducer, the viscosity reduction rate of SP-L in the wide oil-water ratio range of 9:1-1:9 increased by 8.6% -19.5%. Displacement experiments show that the oil recovery efficiency of SP-L combined with subsequent water flooding is 22% higher than that of primary water flooding, and 5.1% higher than that of the JN-P system (0.25 wt% JN-1 + 0.1 wt% HPAM). The viscosity reduction composite flooding system constructed in this paper provides technical support for efficient viscosity reduction and enhanced oil recovery of heavy oil in Xinjiang Oilfield.

  • 1
• Preparation and Property Evaluation of a Polymeric Surfactant for Oil Layers after Polymer Flooding

  CAO Ruibo, PI Yanfu, PAN Feng, LI Bo, YAN Wei

  Abstract: (24) HTML (0) PDF (0.00 ByteKB) (0)

  Abstract:

  To efficiently exploit the approximately 44% remaining reserves in the main oil layers of Daqing Oilfield after polymer flooding, a polymeric surfactant composed of acrylamide (AM), dodecyl acrylamide, 2-acrylamido-2-methylpropanesulfonic acid and dodecyl polyoxyethylene (23) ether acrylate was prepared by using a method involving free-radical aqueous polymerization followed by weak alkaline hydrolysis. The application performance of polymeric surfactant A was compared and evaluated against commercial polymeric surfactant HB, and partially hydrolyzed polyacrylamide (PHPAM). Results demonstrated that the fundamental physicochemical properties of polymeric surfactant A meet the relevant technical standards. Under identical conditions, its viscosity-enhancing capability, salt resistance, and aging stability outperformed those of the comparative polymers. It can reduce oil-water interfacial tension and form an "O/W" (oil-in-water) emulsion with crude oil, with emulsification and water separation properties meeting the requirements of post polymer flooding reservoirs. In the natural Berea sandstone core oil displacement experiment at a concentration of 1000 mg/L and a polymer dosage of 0.5 PV, the enhanced oil recovery value after polymer flooding was 15.1%, which was 3 to 5 percentage points higher than those of the comparison polymers.

  • 1
• Sodium bromide solubilization and construction of high-density sodium bromide brine system

  Ma Jihe, Wang Chaoqun, Zhang Yufei, Guo Jiabao, Hu Zhiyuan, Yang Fan

  Abstract: (34) HTML (0) PDF (0.00 ByteKB) (0)

  Abstract:

  In response to the issue that the density of sodium bromide as a drilling and completion fluid is only 1.52 g/cm3, which is difficult to meet the demand for high-density fluids in deep well operations, this article pro-poses to conduct corresponding solubilization studies on the sodium bromide system using three different solu-bilization methods. Firstly, seven common and low-cost inorganic salts were selected to conduct a solubiliza-tion study on the saturated sodium bromide solution. Then, the solubilization effects of five different types of surfactants and two copolymers on the sodium bromide system were further investigated, and their solubiliza-tion mechanisms were clarified. The research results show that the solubilization effect of the sodium bromide and zinc chloride mixture is the best, which can increase the density of the system from 1.520 g/cm3 to 1.913 g/cm3. When the anionic surfactant LAS-30 and the nonionic surfactant Tween-80 are used in combination, the density of the sodium bromide-zinc chloride complex salt system is further increased to 1.926 g/cm3. When the copolymer AM-AMPS is used to solubilize the sodium bromide-zinc chloride complex salt system, the density can be increased to 1.923 g/cm3. Regarding the solubilization mechanism, when sodium bromide is added to the LAS-30 surfactant, the Zeta potential on the micelle surface increases from -70 mV to -31.73 mV, indicat-ing that the polar shell on the micelle surface and the free ions in the solution have undergone electrostatic ad-sorption. The determination results of the critical micelle concentration (CMC) show that the presence of inor-ganic salts significantly reduces the CMC of the surfactant. For the copolymer system, the microscopic mor-phology changes of the sodium bromide crystals before and after solubilization were compared to analyze whether it causes lattice distortion or complexation.

  • 1
• Biosynthesis of Ag nanoparticles by Scenedesmus and its evaluation on enhancing oil recovery

  CHEN Zihui, CAO Gongze, LIN Junzhang, CHEN Qiongyao, WU Xiaoling, WANG Weidong, SONG Yongting, CAO Yanbin

  Abstract: (21) HTML (0) PDF (0.00 ByteKB) (0)

  Abstract:

  Recently, nanomaterials have attracted significant attention due to their unique properties. Nanoparticles possess advantages such as small particle size and large specific surface area, which can effectively alter the wettability of rock formations and exhibit significant application potential in enhancing oil recovery in oilfields. This study aims to characterize biosynthesized nanoparticles and evaluate their capability for enhanced oil recovery. In this study, Ag+ was reduced to Ag0 by Scenedesmus extract to synthesize Ag NPs. The bio-synthesized Ag NPs were characterized by laser particle sizer, ultraviolet-visible(UV-vis) spectrophotometer, Fourier transform infrared spectroscopy(FT-IR), Zeta potentiometer, Energy-dispersive X-ray spectroscopy (EDX) and Scanning electron microscopy(SEM). Furthermore, their ability to alter the wettability of rock formations was evaluated. Physical oil displacement simulation experiments were conducted to assess their effectiveness in enhancing oil recovery. The results demonstrated that the bio-synthesized Ag NPs were small spherical and elliptical particles with the size between 20~50 nm. The average zeta-potential of the silver nanoparticle system was measured at -21.2 mV, confirming its favorable stability in the reaction medium system. The contact angle on glass slides treated with 600 mg/L silver nanofluid was decreased from 142° to 68°. The bio-nano system combined with rhamnolipid achieved an oil-water interfacial tension of 0.018 mN/m. In low-permeability cores with a permeability of 25×10?3 μm2, the oil displacement efficiency would further enhanced by 15.47% compared with water flooding. Micro-model experiments demonstrated that the bio-nano system can effectively mobilize residual oil after primary water flooding, thereby enhancing crude oil recovery.

  • 1
• Foam Occurrence Morphology and Evolution in Different Fractured-Porous Reservoirs

  MA Guorui, DONG Ruiqiang, ZHAO Yuheng, SUN Haitong, HU Jinchao, WU Weipeng, QU Ming

  Abstract: (22) HTML (0) PDF (0.00 ByteKB) (0)

  Abstract:

  In order to accurately describe the generation, migration and collapse of foam in fractured-vuggy reservoirs at 140°C and 30 MPa for dynamic analysis, this study utilized a self-designed visual fracture-pore model to achieve intuitive capture of foam dynamics. Through conducting nitrogen foam flooding experiments, the morphology and evolution laws of foam were quantitatively characterized. Nitrogen foam flooding experiments were conducted to quantitatively characterize the foam morphology and its evolution. The results show that under pressurized conditions, the half-life of the foam is significantly longer than that under normal pressure conditions. The change in the half-life of the foam is not obvious under low-pressure conditions (5 MPa) compared to high-pressure conditions (30 MPa). Therefore, low-pressure conditions can be used to simulate high-pressure conditions. In fractured-porous reservoirs, when the ratio of fracture width to foam size (W/D) is approximately 1.1 times, the roundness and size distribution of the foam are moderate. The bubbles are completely separated by the liquid film, the foam is distributed in a discrete manner, and it accumulates in an "elliptical" shape. When the W/D ratio is increased to 2.5, the size range of the foam becomes concentrated and it accumulates in a "spherical" shape, exhibiting strong stability and blocking capacity. when the W/D ratio is reduced to 0.5, the foam is strongly compressed by the crack walls and cannot exist in the form of discrete bubbles. The size and roundness variations are significant, and it accumulates in a "single flat ellipsoidal" form. The research shows that in fractured-porous reservoirs, the presence form of bubbles is time-dependent. The shape and stability of the bubbles are closely related to the fracture width and bubble size. When the crack width is greater than 2.5 its size, it generates smaller and more stable foams, and thus effectively seals the crack channels. This study has revealed the time-varying occurrence patterns and critical size matching principles of foams in fracture-pore reservoirs, providing a crucial theoretical basis for the performance optimization of efficient foaming agents in fault-hole type reservoirs and the precise optimization of foam size.

  • 1
• The competitive mechanism of acid dissolution reactions among multiple mineral components in sandstone acidification

  QI Ning, REN Feiyue, JIANG Ping, LI Aihua, SHENG Qiyun

  Abstract: (23) HTML (0) PDF (0.00 ByteKB) (0)

  Abstract:

  There exist complex competitive reactions among two acids and multiple minerals in mud acid acidification of sandstone reservoirs, which makes it difficult to accurately characterize the acid-rock reaction kinetics and provide basic data for the optimal design of sandstone acidification. To reveal the competitive mechanism of acid - rock reactions in sandstone reservoirs, six common sandstone mineral components were selected, and the dissolution rate was taken as the evaluation index. The laws of acid - rock reactions were analyzed through dissolution experiments and XRD diffraction, and the dissolution rates of multiple minerals in sandstone acidification were predicted by machine learning. The study shows that the sequence of dissolution rates of six common sandstone minerals is montmorillonite > kaolinite > chlorite ≈ illite > albite > quartz. When multiple minerals coexist, there is an obvious competitive mechanism among various minerals, which is quite different from the results of single minerals. Clay minerals have stronger competitiveness with acid fluid than quartz and feldspar. Among clay minerals, montmorillonite has the highest competitiveness, followed by kaolinite, and chlorite has higher competitiveness than illite. When albite coexists with chlorite or illite, it exhibits greater competitiveness in reacting with acid solutions compared to when it coexists with other clay minerals. Based on machine learning, a multi-layer perceptron neural network is used to develop a dissolution rate prediction method for sandstone acidification. The method achieves a prediction error of less than 20% and can accurately forecast the dissolution rates of multiple minerals. Research on the competitive mechanism of multi-mineral components and establishment of the dissolution rate prediction method can guide the optimization design of acidification technique for formations with different minerals.

  • 1
• Preparation and Performance Evaluation of VSNPs-P (AM-AMPS) Composite Nano-scale Profile Control Agent

  LIU Yunlong, YAN Changhao, WANG Teng, ZHENG Lijun, WANG Yan, LIU Zhuojun

  Abstract: (38) HTML (0) PDF (0.00 ByteKB) (0)

  Abstract:

  In order to solve the problem of poor application effect of polyacrylamide microspheres (P (AM-AMPS)) due to insufficient strength or elasticity, vinyl silicon nanoparticles composite polyacrylamide microspheres (VSNPs-P (AM-AMPS)) were prepared by reverse micro emulsion polymerization with vinyl silicon nanoparticles (VSNPs), acrylamide (AM), 2-acrylamide-2-methylpropane sulfonic acid (AMPS) and other copolymer components. The results showed that the composite microspheres had a spherical morphology, uniform particles, and an average particle size of 63.3 nm. The swelling ratio was 3.3 times at 20 ℃ and 90000 mg/L mineralization for 72 hours, and 4.2 times at 80 ℃ and deionized water for 72 hours, demonstrating good temperature and salt resistance. Compared with P (AM-AMPS) microspheres, the compressive strength of the composite microspheres is nearly doubled, the elastic modulus is increased by 4.1 times, and the sealing rate of the sand filled tube test is increased by 7.8%, reaching 95.6%. The introduction of VSNPs effectively enhances the mechanical strength and elasticity of composite microspheres, making them possess both swelling deformation and strength toughness, further improving the sealing effect.

  • 1
• Changes in CO₂ huff-n-puff patterns and the distribution characteristics of remaining oil in different fracture zones under the influence of water invasion layers in tight reservoirs

  XIE Shengchen, HUANG Shijun, ZHAO Fenglan, YANG Mingyang, TAO Danfeng

  Abstract: (33) HTML (0) PDF (0.00 ByteKB) (0)

  Abstract:

  After volumetric fracturing of horizontal wells in tight reservoirs, the water in the fracturing fluid seeps into the reservoir and forms a "water invasion layers" in the near-well area, which affects the development effect of CO2 huff and puff. To clarify the influence of the water invasion layers on the effective range of CO2 huff and puff, the core physical simulation experiment method combined with low-field nuclear magnetic resonance imaging technology was adopted to analyze the remaining oil distribution characteristics and T2 spectra of different rounds of CO2 huff and puff, and to explore the influence of the water invasion layers and the coexistence of the water invasion layers and fractures on the effect of CO2 huff and puff and analyze its seepage mechanism. The research results show that in the area without fractures, the existence of the water invasion layers weakens the gravity override phenomenon of CO2 huff and puff, forms a smaller curvature arc-shaped huff and puff front, reduces the effective range and recovery degree of CO2 huff and puff; in the fracture area, the existence of the water invasion layers changes the huff and puff front from elliptical to "U" shape, and also reduces the effective range and recovery degree of CO2 huff and puff, but both are higher than those in the area without fractures; Water invasion layers affect the CO2 huff and puff effect and the range of action by hindering the contact between CO2 and crude oil and influencing the flow velocity distribution of CO2 in the seepage area. Whether in the unfractured area or the fractured area, when the water-invasion layer hinders the contact between CO2 and crude oil, CO2 always tends to break through the water-invasion layer at the location where the local pressure gradient is the largest, the flow velocity is the greatest, and the capillary resistance is overcome first. The research results clarify the distribution characteristics of remaining oil and seepage mechanism under CO2 huff and puff in tight reservoirs under the influence of water invasion layers, and also have certain reference significance for the development of similar oil reservoirs by CO2 huff and puff.

  • 1
• Screening of a Guar Gum Degrading Bacterium and Evaluation of Low-Temperature Gel Breaking Performance by Its Enzymes

  HAN Han, DONG Han, LI Hui, WANG Jiqian

  Abstract: (38) HTML (0) PDF (0.00 ByteKB) (0)

  Abstract:

  Objective: Cross-linked guar gum fracturing fluid requires gel breaking and flowback after fracturing operations, but persulfate-based gel breaking agents face the challenge of low efficiency at low temperatures. Enzym gel breakers can achieve effective degradation of fracturing fluids under low-temperature conditions, serving as a necessary complement or substitute to chemical gel breakers. This study aims to screen highly efficient guar gum-degrading bacteria and subsequently optimize their enzyme production performance, thereby providing novel microbial resources and highly active enzymes for the development of enzymatic gel breakers. Methods: A guar gum-degrading bacterium has been isolated from fracturing flowback fluid and identified through morphological analysis and 16S rRNA gene sequencing. Its optimal medium formula and conditions were determined through single-factor experiments and response surface optimization. β-mannanase was purified through successive steps of ammonium sulfate salting-out and chromatographic techniques. The purified enzyme was then employed for testing its enzymatic activity and gel-breaking efficiency. Results: Based on phylogenetic analysis of the 16S rRNA gene sequence, the bacterial isolate was identified as Exiguobacterium acetylicum. To our knowledge, this study reports the first discovery of guar gum degradation capability in Exiguobacterium acetylicum. After optimizing the culture conditions, including carbon and nitrogen sources and shaking speed, the activity of β-mannanase and biomass of the guar gum-degrading strain increased by 198.82% and 103.09%, respectively. For crosslinked guar gum gel, the purified gel-breaking enzyme achieved a viscosity reduction rate of 92.3% to 95.7% at a low addition amount, 40°C, and pH 10, with a residue content of only 148 mg·L-1, which was 45.5% of that of ammonium persulfate gel-breaking. A complete gel break was achieved with the viscosity of the cross-linked guar gum gel dropping to less than 5 mPa·s. The residual debris from the ammonium persulfate breaking could be further degraded by the enzymatic breaker solution. Conclusion: This study successfully isolated a novel strain of guar gum-degrading bacterium and optimized its culture conditions. The enzyme produced by this strain exhibits excellent low-temperature gel-breaking performance, enabling highly efficient degradation of cross-linked guar gum fracturing fluids at low temperatures with minimal residue.

  • 1
• Green Synthesis of Magnetic Nanoparticles Fe3O4 NPs and Their Application in Oil Removal from Oily Wastewater

  LI Landuo, ZHANG Cenqian, GAO Jie, FU Jian, Han Yuxiao, DENG Shuyuan, WANG Bo, SHE Yuehui

  Abstract: (50) HTML (0) PDF (0.00 ByteKB) (0)

  Abstract:

  In order to develop efficient adsorbents for water body remediation, this paper green-synthesized magnetic nanoparticles Fe3O4 NPs using the low-cost and readily available birch bark extract, and applied them to the oil removal treatment of oily wastewater. The aim of this study is to overcome the challenges of high cost, complex process, and low biodegradability in the preparation of traditional nanomaterials. The synthesized magnetic nanoparticles Fe3O4 NPs were characterized by various methods such as infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results showed that the bioactive substances in the birch bark extract acted as reducing agents and stabilizers in the synthesis of Fe3O4 NPs. The prepared Fe3O4 NPs were irregularly spherical in shape, with an average particle size of 16.69 nm. Their Zeta potential was -31.7 mV, indicating good stability. The saturation magnetization of Fe3O4 NPs was 30.2 Am2/kg, and the magnetization curve indicated that the material had superparamagneticsm, making it easy to separate and recover. The optimal conditions for oil removal by the synthesized Fe3O4 NPs were: concentration 500 mg/L, temperature 50℃, treatment time 30 min, and stirring speed 200 r/min. The oil removal rate was 90.24%, demonstrating excellent oil removal performance. This indicates that Fe3O4 NPs are a good oil removal material. This study ingeniously integrates the advantages of nanotechnology, biotechnology, and green chemistry, providing a new approach for the green treatment of oily wastewater.

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• Preparation and Performance Evaluation of Lignin-Based Dual-Crosslinked Polymer Gel for CO2 Channeling Control in High-Temperature Oil Reservoirs

  QIU Jiajun, QING Xiaoyun, HUANG Wanyun, HU Mengting, WANG Qinpei, LI Liang, WEI Bing, WEN Yangbing

  Abstract: (125) HTML (0) PDF (0.00 ByteKB) (0)

  Abstract:

  To address the gas channeling problem in CO2 flooding for low-permeability reservoir development and the easy hydrolysis issue of water shutoff gels under high-temperature and high-salinity conditions, this study prepared a lignin-based double-cross-linked polymer hydrogel (L-PAM-PDEAEMA) resistant to CO2 gas channeling and suitable for high-temperature reservoirs. The preparation used lignin (Lignin), diethylaminoethyl methacrylate (DEAEMA), and acrylamide (AM) as raw materials via cross-linking reaction. Experiments on the CO2 sensitivity, acid resistance, temperature and salt resistance of the hydrogel were conducted using a self-made 200 mL/16 MPa high-temperature and high-pressure reactor (equipped with a gas inlet valve and a pressure gauge). Its mechanical properties were tested by a universal tensile testing machine and a texture analyzer, the reaction mechanism was analyzed by FTIR and XPS, and the structural changes were confirmed by SEM characterization. This study investigated the effect of DEAEMA on the CO2 sensitivity of the hydrogel and the effect of Lignin on its acid resistance, temperature resistance and salt resistance. It was verified that the introduction of DEAEMA and Lignin into the polyacrylamide network can provide a new technical approach for the preparation of hydrogels with both acid resistance and high-temperature and high-salt resistance properties. The research results show that after CO2 treatment under the conditions of 130℃ and 6 MPa, which simulate the actual development environment of oilfields, the compressive strength of the L-PAM-PDEAEMA hydrogel can be significantly enhanced. Meanwhile, it is proved that the hydrogel has excellent temperature resistance and acid resistance. When the addition amounts of Lignin and DEAEMA are 10% and 20% of AM (by mass fraction) respectively, the compressive strength of the CO2-treated L10-PAM-PDEAEMA hydrogel increases from 16 KPa to 151 KPa, with an increase of approximately 8.4 times. FTIR and XPS analyses indicate that the hydrogel forms new ionic cross-linking and hydrogen bonds after CO2 treatment, and the synergistic effect of the two significantly enhances its physical properties. SEM characterization shows that the micro-pores of the hydrogel become denser after treatment, which further confirms its excellent CO2 sensitivity. The hydrogel can still maintain excellent stability after being statically placed for 7 days under the conditions of 130℃, 6 MPa and saline water with a salinity of 21×104 ^mg/L. Tests by a texture analyzer show that its compressive force at 50% strain is 3 N. This study provides a new technical approach for the preparation of hydrogels with combined CO2 sensitivity, acid resistance, temperature resistance and salt resistance, and shows promising application prospects in the control of CO2 gas channeling in low-permeability oilfield reservoirs.

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• Research on the Separation and Quantitative Method of Oil-Soluble Tracers for Oilfield Application Based on Gas Chromatography Technology

  LI Yang, LI Jianrong, LI Rongqiang, LUO Shuifa, GAO Xiaoming, LI Kexing, ZAIROV Rustem, WU Jundao, Anastasiya Bebyakina, YUAN Chengdong

  Abstract: (88) HTML (0) PDF (0.00 ByteKB) (0)

  Abstract:

  Gas chromatography technology was employed to screen solvents for extracting 38 types of oil-soluble tracers from crude oil. Methanol was selected as the tracer solvent due to its minimal extraction of crude oil components and the least signal interference. The aqueous solution formed by water in the oil and methanol severely affects tracer extraction, and residual crude oil components extend the analysis cycle to 10 hours. Therefore, further optimization of the tracer extraction method is needed. By adding 20% mass ratio of isooctane and excess K2CO3 to crude oil containing 1000 ppm tracers, and then using stirring, ultrasonic bath, and centrifugation to dehydrate the crude oil, followed by freezing the methanol extract at -32°C, tracer analysis in crude oil was conducted. This achieved precise separation and quantification of all tracers within 5 hours in the gas chromatogram. Experimental results demonstrate that using gas chromatography technology and solvent extraction can rapidly qualitatively and quantitatively analyze up to 38 oil-soluble tracers in crude oil in a single injection, thus monitoring crude oil flow and achieving reservoir characterization.

  • 1
• Biomimetic preparation and performance evaluation of thermosensitive modified polymer microspheres

  HAN Dong

  Abstract: (103) HTML (0) PDF (0.00 ByteKB) (0)

  Abstract:

  To address the challenges of enhanced heterogeneity and severe water channeling in high water-cut oilfield reservoirs, a thermally sensitive modified polymer microspheres with both thermosensitive responsiveness and high retention capacity was developed to achieve deep selective water shutoff and improved oil recovery. A microfluidic in situ emulsion polymerization combined with PDA surface coating was employed as the bioinspired design strategy. By adjusting surfactant concentration and oil–water ratio, precise particle size matching was realized, and functional monomers were synergistically incorporated to construct a thermosensitive and salt–alkali adaptive composite structure. The microspheres were systematically characterized in terms of morphology, Zeta potential, FTIR, thermogravimetric performance, phase transition temperature, shear resistance, wettability, and interfacial tension. Results showed that the modified microspheres had a median particle size of approximately 800 nm, a higher absolute surface potential, and stable dispersion, with significantly enhanced thermal stability and shear resistance. At a concentration of 2wt%, the microspheres achieved optimal wettability and the lowest oil–water interfacial tension. Laboratory core flooding experiments at 120 °C demonstrated that injecting 0.5 PV of 2wt% microspheres reduced water cut by about 20% and increased recovery factor by about 15%. Field applications in three wells confirmed that, under high-temperature and high-salinity conditions, the microspheres significantly increased injection pressure, reduced water cut, and achieved a cumulative oil increment of 1.64×105 t. These findings indicate that the thermally sensitive modified polymer microspheres exhibit excellent thermal–salinity adaptability and targeted water shutoff efficiency, providing an effective technical approach for deep profile control and enhanced oil recovery in high-permeability reservoirs.

  • 1
• The Oil-Displacing Capacity and Corrosion Inhibition Behavior of Bacillus velezensis

  Xie Juan, Yang Wen, Guo Ge, Chen Ying, Li Jiangang

  Abstract: (136) HTML (0) PDF (0.00 ByteKB) (0)

  Abstract:

  Objective To address the intensified steel corrosion that accompanies microbial enhanced oil recovery (MEOR), a strain of Bacillus velezensis (designated 4-19) was isolated from produced water in the Changqing Oilfield. Its oil-displacement efficiency and the synergistic corrosion-inhibition mechanism on J55 carbon steel were investigated. Methods Crude-oil viscosity reduction, SARA (saturates, aromatics, resins, asphaltenes) fractionation and gas chromatography were employed to characterize the degradation of heavy fractions. Weight-loss measurements, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) were used to elucidate the corrosion-inhibition behavior. An equivalent circuit model combined with energy-dispersive X-ray spectroscopy (EDS) was applied to reveal the protective film mechanism. Results Strain 4-19 lowered the crude-oil surface tension by 54.5 % and achieved a 69 % degradation rate within three days. Viscosity at 35 °C and 40 °C was significantly reduced; the relative molecular masses of aromatics and resins decreased by 17.61 % and 18.60 %, respectively. The corrosion rate of J55 steel declined by 76.23 %. EIS indicated that the film resistance (Rb) increased by 42.6 % and the polarization current density decreased by 76.7 %. Conclusion B. velezensis 4-19 secretes lipopeptide biosurfactants that degrade heavy fractions while simultaneously consuming dissolved oxygen, forming a compact corrosion-product film. This coupling of oil recovery and corrosion inhibition offers a novel strategy for field-scale MEOR applications.

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• Research Progress on the Diffusion of CO2 in Crude Oil

  DU lin，LIU wei，CHEN Xingyi，QING Xiaoyuan，REN Xuefei

  2019,36(2):367-372, DOI: 10.19346/j.cnki.1000-4092.2019.02.034

  Abstract: (1450) HTML (0) PDF (1.44 MKB)(5103)

  Abstract:

  Diffusion of CO2 in oil phase plays an important in enhanced oil recovery，since its impact on the recovery improvement percentage and oil viscosity reduction percentage. The research progress on the CO2 diffusion coefficient measurement methods including direct method and indirect method，were summarized. The difference of mathematic models and research progress of indirect method were pointed out in this paper. Based on the summary，it is pointed out that the improving the analysis of impact factors，enriching the research dimension，and improving the study of diffusion law in different scale pores will become the focus and hotspot of the future.

• Optimization and Application of Strong Plugging Drilling Fluid for Horizontal Well in Tight Oil of Yanchang Oilfield

  ZHANG Wenzhe1，2，LI Wei1，2，WANG Bo1，2，LIU Yun3

  2019,36(2):191-195, DOI: 10.19346/j.cnki.1000-4092.2019.02.001

  Abstract: (1793) HTML (0) PDF (1.23 MKB)(4054)

  Abstract:

  In order to speed up the development of tight oil and improve the horizontal well drilling technology of tight reservoir in Yanchang oilfield，meanwhile，aiming at the polyacrylamide potassium salt（K-PAM）polymer drilling fluid system used in the current stage of Yanchang oilfield had shortcomings such as poor rheology，insufficient plugging and inhibition，the indoor optimization of the commonly used fluid loss reducer，inhibitor，lubricant，plugging agent and other treatment agent was preferred to obtain a formula of strong plugging type nano-polymeric alcohol water-based drilling fluid suitable for tight reservoir. Finally，the drilling fluid was applied in the field. The results showed that the polymer fluid loss additive COP-FL could significantly improve the water loss and wall-forming property of the system. The non-fluorescent anti-collapse lubricant FT342 had strong inhibition. The liquid extreme pressure lubricant JM-1 had good overall lubrication effect. And blocking agent anhydrous polymeric alcohol WJH-1 and nano-emulsion RL-2 could increase the drilling fluid blocking rate by 51.7%，which could enhance the wellbore stability. The horizontal section strong plugging type drilling fluid system，whose formula was 4% sodium bentonite，0.2% soda ash，0.4% K-PAM，2% COP-FL，1.5% FT342，1.0% JM-1，5% WJH-1 and 3% RL-2，was applied to two horizontal wells in tight reservoir of Yanchang oilfield. During the construction process，the system had good leakage prevention and sealing effect. The mechanical drilling speed increased by 30% compared with the adjacent one，the construction period shortened by 35% ，the downhole accident rate reduced by 85.7%，and the drilling cost reduced by 34.7%，which provided effective technical support for the excellent drilling of horizontal wells in tight reservoir of Yanchang oilfield.

• Microscopic Flooding Mechanism Experiment Visualization of 2-D Smart Black Nano-card

  WU Weipeng1，2，HOU Jirui1，2，QU Ming1，2，WEN Yuchen1，2，LIANG Tuo1，2，YANG Jinbin1，2，ZHAO Mengdan1，2

  2020,37(1):133-137, DOI: 10.19346/j.cnki.1000-4092.2020.01.023

  Abstract: (1796) HTML (0) PDF (2.35 MKB)(3995)

  Abstract:

  The 2-D smart black nano-card is a new nanosheet material which is independently developed by the institute of enhanced oil recovery from china university of Petroleum（Beijing）. The nano-card has the advantages of small size（80×60×1.2 nm）and large specific surface area（57 m2/g）. In this paper，2-D smart black nano-card displacement experiments was carried out with different porosity and permeability two-dimensional visualized models. Through analyzing the influence factors such as core permeability， particle concentration and injection rate on oil displacement effect，the migration rules and microscopic seepage mechanism of the 2-D smart black nano-card system were studied. The experiment results revealed that the nano-card had advantage hydrophile-lipophile balance（HLB）. The wettability of the rock surface could be changed，the wedge osmotic pressure could be generated by the two-phase interface，and the microscopic cyclotron could be formed. Besides that，nano-card had enormous surface contact compared with previous spherical nanoparticles such as SiO2. Therefore，nano-card could effectively displace the remaining oil from the formation，peel off the oil film on the throat wall on micro pores，expand the sweep volume of the low permeability layer，and thus，improve the degree of the crude oil recovery.

• Common Problems and Solutions on Writing of Scientific Papers

  YANG Mingjiao，LIN Zhangbi

  2019,36(1):188-190, DOI: 10.19346/j.cnki.1000-4092.2019.01.035

  Abstract: (2461) HTML (0) PDF (1.15 MKB)(3882)

  Abstract:

  From the perspective of editorial practice，common problems in the major part of scientific paper，including abstract， introduction，experiments，result and discussion，conclusion，were analyzed. In order to improve the researchers’writing level，a method of using mind mapping to clear the writing thoughts was put forward.

• Preparation and Performance Evaluation of Helper-breaking Capsule Type Shielding Temporary Plugging Protection Agent in Fracturing

  ZHANG Rusheng1，WANG Zengbao2，3，ZHAO Mengyun1，LIU Changyin1，SUN Zhiyu1，JI Yuan2，ZHAO Xiutai2

  2019,36(2):225-229, DOI: 10.19346/j.cnki.1000-4092.2019.02.007

  Abstract: (1370) HTML (0) PDF (1.32 MKB)(3655)

  Abstract:

  In order to reduce the damage to the reservoir caused by the leakage of fracturing fluid and the solid phase residue after breaking the gel，based on the shielding temporary plugging oil and gas layer protection theory and the characteristics of microcapsule breaker，the helper-breaking capsule type shielding temporary plugging protection agent in fracturing named TD-1was prepared by liquid drying method，which used organic acid as the core material，ethyl cellulose as the capsule material，polyethylene pyrrolidone as the porogen，and polyvinyl alcohol as the protective agent. The preparation condition was optimized and the performance of TD-1 was evaluated. The results showed that the main particle size of TD-1 was about 300 μm，the content of organic acid in coated core material was 34.1%，and the release rate was 69.0%，when TD-1 was synthesized under the condition of 2.0% polyvinyl alcohol，4.0% ethyl cellulose and polyvinyl pyrrolidone，and 500 r/min stirring rate. TD-1 was helpful for gel breaking of fracturing fluid，which could reduce the viscosity of fracturing fluid by 35.6% and the solid residue content by 44.9%. Meanwhile TD-1 had little effect on the viscosity of fracturing fluid and gel breaking time. TD-1 could form a temporary plugging zone on the surface of reservoir，which could reduce the invasion damage caused by the fracturing fluid filtrate and solid phase material. TD-1 improved the permeability recovery rate by 11.32% and made the core permeability recovery rate reached 82.47%，showing good effect on temporary shield plugging reservoir.

• Research Progress on Shale Inhibitors at Home and Abroad in Recent Ten Years

  MA Jingyuan, PAN Yidang, YU Peizhi, AN Yuxiu

  2019,36(1):181-187, DOI: 10.19346/j.cnki.1000-4092.2019.01.034

  Abstract: (1582) HTML (0) PDF (1.20 MKB)(3582)

  Abstract:

  From the aspects of amine inhibitors，nanocomposites and other inhibitors，the research status of new shale inhibitors at home and abroad and some inhibitor evaluation methods were reviewed. The inhibition mechanism of various inhibitors was analyzed. In general，the hydration expansion and dispersion of shale was inhibited by various inhibitors mainly from both chemical and physical aspects，thereby improving shale stability

• Research Progress on Influencing Factors of Emulsion Stability with Molecular Dynamics Simulation

  WANG Zhihua1，2，XU Yunfei1，QI Xiangdong1，LIU Xiaoyu1，HONG Jiajun1

  2021,38(2):360-367, DOI: 10.19346/j.cnki.1000-4092.2021.02.028

  Abstract: (1891) HTML (0) PDF (2.17 MKB)(3433)

  Abstract:

  The stability of emulsions presents a significant challenge in surface process particularly，both in terms of crude oil dehydration and produced water treatment. Considering the potential influence of asphaltene and resin in crude oil，especially the polymer and surfactant would be appeared in actual produced emulsions in chemical flooding process. This paper reviewed the application and research progress of molecular dynamics simulation in the field of oil- water interface stability mechanism. The available methods and relevant software for characterizing the visualization，density distribution，radial distribution function，oil water interface formation energy，and molecular diffusion coefficient were discussed，respectively. In order to understand the interphase interaction of crude oil emulsions and address it，the molecular dynamics simulation could be used as an effective method according to the existed research. The review indicated that breaking through the limitations of model simplification and single factor simulation to understand the molecular adsorption，droplet coalescence，and droplet separation from micro-scale was a research application and development direction of molecular dynamics simulation in the fields of oil- water emulsification and demulsification. Furthermore，the component properties of internal phase and external phase，and the temperature and pressure conditions need to be considered.

• Development and Application of Heavy Oil Viscosity Reduction Technology at Home and Abroad

  ZHOU Linbi，QIN Bing，LI Wei，WANG Zheng

  2020,37(3):557-563, DOI: 10.19346/j.cnki.1000-4092.2020.03.032

  Abstract: (949) HTML (0) PDF (1.18 MKB)(3331)

  Abstract:

  Viscosity reduction and mobility improvement are very crucial in heavy oil recovery. The mechanism，development and application of main viscosity reduction methods at home and abroad were discussed and compared，including thermal treatment based on steam injection，fire flooding，emusification，catalytic reaction，solvent dilution and microbial viscosity reduction. The characteristics and disadvantages of these methods were summarized. Finally，the development directions of heavy oil viscosity reduction technology were proposed.

• Status of Enhanced Oil Recovery Technology by In-situ CO₂ Generated in the Formation

  JIN Fayang，ZHOU Shunming，GAO Shibo，YAO Zheng，WANG Ruilin

  2021,38(3):564-570, DOI: 10.19346/j.cnki.1000-4092.2021.03.033

  Abstract: (602) HTML (0) PDF (1.25 MKB)(3136)

  Abstract:

  In view of the shortcomings of conventional CO₂ flooding，domestic and foreign scholars have proposed in-situ CO₂ generation technology and done a lot of research. This technology is a new technology that spontaneously produces CO₂ or foam in the reservoir to displacement oil through the interaction of chemical agents，it has the advantages of no natural CO₂ resources required，controllable gas production，simple process，good injection，and strong adaptability，it is a promising enhanced oil recovery technology. Based on in-depth research，this paper reviews the research progress on the CO₂ gas production system in recent years and the mechanism of the self-generated CO₂ flooding technology.

• Research Progresses on Improving Steam-assisted Gravity Drainage Application for Heavy Oil Recovery

  SHU Zhan，PEI Haihua，ZHANG Guicai，GE Jijiang，JIANG Ping，CAO Xu

  2020,37(1):185-190, DOI: 10.19346/j.cnki.1000-4092.2020.01.032

  Abstract: (1270) HTML (0) PDF (1.02 MKB)(3103)

  Abstract:

  Steam-assisted gravity drainage（SAGD）technology is widely used in the production of ultra-heavy oil，but there are problems such as severe steam channeling and low heat utilization during the development process. By summarizing the current main technical methods to improve the development effect of SAGD，such as gas-assisted SAGD technology，solvent-assisted SAGD technology，foam-assisted SAGD technology and chemical additive-assisted SAGD technology，the mechanism of improving SAGD technology and the effect of improving recovery efficiency were introduced. The existing problems and suggestions for use were put forward. The differences between reservoir geological conditions and construction conditions should be considered comprehensively，and different auxiliary SAGD technologies should be selected to maximize the economic benefits.

• Research Progress of Enhancing Oil Recovery Mechanism by Using Nanofluids

  ZHANG Jingnan1，2，TIAN Lei3，ZHANG Hongwei1

  2021,38(1):184-190, DOI: 10.19346/j.cnki.1000-4092.2021.01.034

  Abstract: (2163) HTML (0) PDF (2.12 MKB)(3051)

  Abstract:

  Nanofluid flooding is of great significance to reduce the cost of oil development and enhance oil recovery. A series of important results have been achieved about the research on the mechanism of nano-fluid flooding. This paper focuses on the basic research related to the nanofluid flooding mechanism. And the four mechanisms of nanofluid enhanced flooding are summarized based on the different academic opinions and research results. According to this，it is pointed out that under the combined effects of structural separation pressure，rock wetting change and reduced oil-water interfacial tension，the nanofluid exhibits the dual characteristics of“roll-up”and“diffusion”in the process of oil displacement，thus having enhanced oil displacement. Finally，it is pointed out that nanofluids will have a very broad application prospect in the field of enhancing oil recovery，but a lot of research is needed on the effect and influencing factors of nanofluid flooding. In addition，the effective combination of nanofluid flooding and foam flooding is a way to enhance oil recovery.

• Field Application and the Performance of Biological Enzyme Double Breakdown Technology at High Temperature

  LIU Yi1，2，LUO Cheng1，LI Liangchuan1，2，WU Jun1，2，WU Zuohao1，YAN Fei1，2，DAN Jiamin1，2

  2019,36(3):394-399, DOI: 10.19346/j.cnki.1000-4092.2019.03.003

  Abstract: (1531) HTML (0) PDF (2.10 MKB)(2794)

  Abstract:

  Aiming at the problem of gel nonuniform breaking using ammonium persulfate（APS）at fracturing fluid in Gaoshangpu oilfield，a gene fragment of β-mannan enzyme was extracted from marine thermophilous bacteria. The gel breaking principle of APS and biological enzyme was analyzed by means of GPC and electrospray ionization mass spectrometry. The proper temperature and the range of pH vale of β-mannan enzyme was researched. The fracturing fluid prepared with guar gum，biological enzyme，capsule breaker and other additives was applied in some deep wells of Gaoshangpu oilfield. The results showed that mannan enzyme was endonuclease. The viscosity and molecular weight of guar gum were greatly reduced by intersecting action which directly affected on the glycosidic bond and mainly produced 2—6 oligosaccharides with few monosaccharide. While APS preferred to break the C—C bond on the sugar ring. β-mannan enzyme tolerated 120℃ and 4—10.5 pH value. The optimum temperature was 70℃ and the pH value was 6—7. The enzyme activity at 120℃ was 40% of the highest enzyme activity，and the activity could maintain 55 min. While when the temperature was 90℃，the activity maintaining time increased to 180 min. Adding APS and biological enzyme into the fracturing fluid could reduce 22%—45% residue content. When the fracture was completely closed，the technology of injecting high concentration biological enzyme acquired effective stimulation in 9 fractured wells. The average injection pressure initially decreased about 13 MPa，the average cumulative injection quantity was 1.2×10⁴ m³，and the validity was 290 days.

• Treatment and Reuse of Guar Gum Fracturing Flow-back Fluid Using the Technology of“Water Quality Regulation-flocculation-ozone Oxidation”

  MA Zhenpeng1，LI Hui1，YANG Zhigang1，YU Tiantian2，MA Tianqi1，ZHANG Shuxia1

  2019,36(2):215-218, DOI: 10.19346/j.cnki.1000-4092.2019.02.005

  Abstract: (1269) HTML (0) PDF (1.28 MKB)(2746)

  Abstract:

  Based on the analysis of the water quality characteristics of the guar gum fracturing flow-back fluid（GGFFBF）from acertain oil well in Yanchang oilfield，the process of water quality regulation-flocculation-O₃ oxidation was carried out to treat the GGFFBF and the treated GGFFBF was reused to prepare the slick water fracturing fluid. The effects of various process parameters on the treatment effect were explored. The results showed that when adjusting the pH value of the 500 mL GGFFBF to 9.0 and adding 800 mg/L flocculant IF-A and 1.0 mg/L coagulant FA-B，and then pumping O3 for 40 min at a speed of 30 mL/min，the treated GGFFBF was colorless，clear and transparent，and the water quality was good. The SS content was less than 3.0 mg/L，the Feion content was below 0.5 mg/L，the viscosity was reduced to 1.28 mPa·s，and the bacterial content was low. The slick water fracturing fluid was prepared with the treated GGFFBF，and the performance of the slick water fracturing fluid was similar to that of the slick water fracturing fluid prepared with tap water，according with DB.61/T 575—2013 standard. The treated GGFFBF met the requirements for water preparation for slick water fracturing fluid.

• Preparation and Performance Evaluation of Cationic Polymer Chromium Gel

  XU Yuande，GE Jijiang，SONG Longfei，ZHANG Yuhao，DU Xiaojuan

  2019,36(2):230-235, DOI: 10.19346/j.cnki.1000-4092.2019.02.008

  Abstract: (1369) HTML (0) PDF (1.38 MKB)(2679)

  Abstract:

  In order to deal with the issue that high strength chromium gel always had high crosslinking speed，the formula of plugging agent was optimized by selecting cationic polymer and using of alumina sol. The chromium gel plugging agent suitable for deep profile control was developed and its performance was evaluated. The results showed that for acrylamide （AM）/ acryloyloxyethyltrimethylammonium chloride（DAC）binary copolymer organic chromium gel，the lower the cationic degree，the longer the gelation time was. Alumina sol could effectively delay the gelation time of cationic polymer chromium gel and improve its strength and long-term stability. The optimum formula of chromium gel system was 0.8% polymer Y5 with 5% cationic degree， 0.3% chromium acetate and 0.2% aluminum sol. The gelation time was 55 h at 90℃ and the elastic modulus was 16.6 Pa，which belonged to high-strength gel. The plugging agent had good injection ability and strong shear resistance. Meanwhile，it had strong temperature and salt resistance，and its blocking rate could reach more than 96%. This plugging agent had long gelation time and strong plugging performance，which could satisfy the requirements of deep profile control.

• Progress and Prospect of Reuse Technology of Fracturing Flowback Fluid

  YAO Lan1，LI Huanxiang1，JIAO Wei2，ZHOU Jiang2，KE Congyu3，ZHANG Qunzheng3

  2022,39(3):548-553, DOI: 10.19346/j.cnki.1000-4092.2022.03.028

  Abstract: (1506) HTML (0) PDF (1.22 MKB)(2638)

  Abstract:

  With the increasing expansion of the development scale of oil and gas fields，the contradiction between the gradual increase of water consumption for fracturing operation and the large amount of fracturing flowback fluid that cannot be directly discharged is further highlighted. It is undoubtedly an effective way to solve this problem that treat the flowback liquid and reuse it. Aiming at the reuse research and application status of fracturing flowback fluid in China，this paper systematically introduced the technical problems faced in the process of flowback fluid treatment，the research and development of recyclable fracturing fluid system，the improvement of flowback fluid treatment process and treatment device. Treating and reusing the flowback liquid was the best way and was also the inevitable trend of future development of oil and gas field industry. The development of flowback fluid reuse technology should start from the research and development of recyclable fracturing fluid system and the improvement of flowback fluid reuse treatment process，so as to further improve and popularize the application of this technology in the process of oil and gas field development. In view of the problems existing in the current reuse technology of flowback liquid，some suggestions were put forward in order to provide guidance for the development of reuse technology of flowback liquid in China.

• Rheological Properties of Erucamidopropyl Dimethylamine Modified Carboxymethyl Hydroxyethyl Cellulose Solutions

  FAN Yue1，JIN Hao1，FANG Bo1，LU Yongjun2，QIU Xiaohui2，SUN Rui1

  2019,36(2):209-214, DOI: 10.19346/j.cnki.1000-4092.2019.02.004

  Abstract: (1692) HTML (0) PDF (1.78 MKB)(2586)

  Abstract:

  To improve the thickening ability and crosslinkingperformance of cellulose，widen its application in fracturing fluid field，a new kind of hydrophobic etherifying agent（3-chloro -2-hydroxypropylerucylamideammonium acetate was prepared to modify carboxymethyl hydroxyethyl cellulose （CMHEC）. Hydrophobic erucamidopropyl dimethylamine carboxymethyl hydroxyethyl cellulose （ED-CMHEC） was first prepared. The rheological and crosslinking experiments of CMHEC and ED-CMHEC were carried out. The results showed that ED-CMHEC solutions exhibited higher viscosities，more apparent thixotropy and viscoelasticity，compared to CMHEC solution. At the mass fraction of 0.3% ，the viscosity of CMHEC and ED-CMHEC solutions at the temperature of 30℃ and at the shearing rate of 170 s^-1were 18.0 mPa·s and 71 mPa·s，respectively. The shear thinning behaviors of CMHEC and ED-CMHEC solutions at different concentrations could be well described by Cross model. Under the same crosslinking conditions that the dosage of zirconium organic crosslinker was 0.2%，the viscosity of gel formed by 0.3% ED-CMHEC solution was 2.4 times than that by 0.3% CMHEC solution，which indicated that ED-CMHEC had a stronger crosslinking performance.

• Research and Application of Liquid Desulfurizer for Water Injection in Bohai Oilfield

  HU Ting

  2019,36(2):277-279, DOI: 10.19346/j.cnki.1000-4092.2019.02.017

  Abstract: (1139) HTML (0) PDF (1.22 MKB)(2572)

  Abstract:

  In view of the high concentration of hydrogen sulfide in water injection system of an oilfield in Bohai Sea，the modified triazine liquid desulfurizer and polyphosphate scale inhibitor were selected by measuring the desulfurization efficiency of desulfurizer on injected water and the effect of scale inhibitor on calcium ion concentration in injected water. Furthermore，the field pilot test was carried out on platform C where was the location of water injection well. The results showed that the desulfurization efficiency of modified triazine liquid desulfurizer for injected water was 98.1%，and the desulfurization effect was the best，but the concentration of calcium ion in water would reduce and scaling would occur. While used with polyphosphate scale inhibitor，the deposition of calcium ion could be significantly reduced. During the pilot test of the platform，the dosage of desulfurizer and scale inhibitor was 500 mg/L and 20 mg/L respectively. The concentration of hydrogen sulfide in the water source well system reduced from 800 mg/m³ to about 20 mg/m³，and the amount of hydrogen sulfide in the production fluid reduced from 150 mg/m³ to about 4mg/m³，which met the desulfurization requirement of the platform and avoided depositing scale.

• Performance Evaluation and Application of Pressure-lowering and Injection-increasing Agent in Low Permeability Reservoir of Jidong Oilfield

  LIU Jing1，2，LIU Yi1，2，LI Liangchuan1，2，WANG Jinzhong1，2，ZHANG Xia1，2，TANG Cong1，2

  2019,36(2):271-276, DOI: 10.19346/j.cnki.1000-4092.2019.02.016

  Abstract: (1115) HTML (0) PDF (1.33 MKB)(2547)

  Abstract:

  Aiming at the problems of rapid rising of water injection pressure and under-injection during the process of water injection in Gaoshangpu oilfield，a cationic-nonionic surfactant and pressure-lowering and injection-increasing agent JDZC was designed through the physical characteristics of low permeability reservoir in Jidong oilfield. The effects of JDZC dosage on surface tension，oil-water interfacial tension and emulsifying ability，and the temperature resistance，pressure-lowering and injection increasing ability of JDZC were studied. Finally，JDZC was applied in the field. The results showed that the temperature resistance of JDZC made from polyoxyethylene ether nonionic surfactant and rosin-based triquaternary ammonium salt could reach 130℃. With the increase of JDZC dosage，the surface tension of JDZC solution decreased and stabilized gradually. The surface tension of 500 mg/L JDZC solution was 28 mN/m. The critical micelle concentration of JDZC solution prepared with injected water in Jidong oilfield was 1000 mg/L. The minimum interfacial tension between 500—5000 mg/L JDZC solution and Jidong crude oil was maintained in the order of 10^-2 mN/m. The emulsifying ability of JDZC to crude oil was good，and the larger the dosage，the stronger the emulsifying ability was. JDZC had obvious effect of reducing pressure and increasing injection for the core of Gaoshangpu main formation. The permeability of core after washing increased by 40% and the pressure decreased by 26%. The field application results of 38 wells showed that the field implementation efficiency was 94%，the initial injection pressure of water injection wells decreased by 8.5 MPa on average，the validity period was more than half a year，and the average enhanced injection of single well was more than 2×10³ m³，which improved the water injection problem of Gaoshangpu low permeability reservoir.

• Preparation and Oil Displacement Properties of OleicAcid-modified Nano-TiO2

  FENG Xiaoyu1，2，3，HOU Jirui1，2，3，CHENG Tingting1，2，3，ZHAI Haoya1，2，3

  2019,36(2):280-285, DOI: 10.19346/j.cnki.1000-4092.2019.02.018

  Abstract: (1555) HTML (0) PDF (1.65 MKB)(2517)

  Abstract:

  Nanoparticle flooding technology has a good oil displacement effect in low permeability reservoirs，but the problem of nanoparticles agglomeration in aqueous solution and blocking small pores in the formation has not been well solved. Low-cost oleic acid is used herein to surface modification of nano-TiO2 for reducing the agglomeration of nanoparticles，and the oil displacement system was optimized through low-permeability core simulation flooding experiment. The results showed that when the molar ratio of oleic acid to nano-TiO2 was 1∶1 and reacted at 60℃ for 4 h，the obtained modified nano-TiO2 had the longest stabilized dispersion time in aqueous solution. Infrared spectroscopy confirmed that the oleic acid group was successfully grafted onto the surface of nano-TiO2 . SEM and Zeta potential indicated that the dispersibility and stability of the modified nano-TiO2 particles was greatly improved. The particle size test results showed that the average particle size of nano-TiO2 in aqueous solution was 246.7 nm. the contact angle of unmodified nano-TiO2 and modified nano-TiO2 system with mass fracion of 0.05% on the surface of hydrophilic slide was 29.95o and 81.44 o，respectively，and the interfacial tension value was 0.475 and 0.74 mN/m，respectively，which explained the mechanism of enhancing oil recovery of the modified nano-TiO2 was still mainly relying on changing rock wettability and reducing oil-water interfacial tension. As for the low peameability reservoir with peameability of 9×10-3～12×10-3μm2，the reasonable injection parameters of the displacement system was 0.1% modified nano-TiO2+0.05% OP-10，and the reasonable injection volume was 0.3 PV，at this time，the enhanced oil recovery reached up to 15%. The nano-TiO2 solution could not only reduce the pressure of the injected water，but also improve the recovery rate of low-permeability core.

• Progress on pH Responsive Smart Gels as Sealants for CO2 Geologic Storage

  ZHAO Li1，LIU Qi1，MA Zhongcheng2，PENG Bo1

  2020,37(2):374-380, DOI: 10.19346/j.cnki.1000-4092.2020.02.033

  Abstract: (968) HTML (0) PDF (1.45 MKB)(2500)

  Abstract:

  Carbon dioxide capture，utilization and storage（CCUS）technology is of great significance for the mitigation of climate change. However，CO2 leakage may occur during gas injection and storage. The failure of wellbore integrity is the main way of CO2 leakage. At present，the research of wellbore cement integrity is mostly about the modification of anticorrosive cement system or cement squeezing. Thus，choosing polymer gel with better inject ability，stronger stability and lower cost can prevent and repair the failure wellbore. Smart polymer gels are currently receiving widespread attention，which can respond intelligently to changes in the formation environment. When the pH of the formation changes，the hydrogel will swell and expand，and the shape will become larger，thereby achieving effective sealing of the failure cement. The research progress of sealants for carbon dioxide geological storage was introduced in detail in this study，and the sealing mechanism and sealing performance of pH-responsive gels were critical reviewed，and then the future development direction and application prospects were discussed as well.