Volume 43,2026 Issue 1

• Biomass Synthetic-based Drilling Fluid Technology in Dongpu Depression

  ZHOU Qicheng, ZHANG Yi, SHAN Haixia, RAN Maolin, WANG Li, WEI Hua, MA Jin, WANG Jinjie

  2026,43(1):1-7, DOI: 10.19346/j.cnki.1000-4092.2026.01.001

  Abstract: (71) HTML (0) PDF (0.00 ByteKB)(0)

  Abstract:

  Based on the geo-engineering integration approach，aiming at the challenges in the Dongpu Depression，such as complex geological structure，numerous faults，deep burial，thin sand body，and instability-prone sand-mudstone interbeds，a temperature-resistant 180 ℃biomass synthetic-based drilling fluid suitable for Dongpu Depression using the biomass synthetic-based fluid LAE-12 as the continuous phase，and the ultrafine calcium carbonate with multi-stage particle size was used to compound with the nano-film-forming plugging material，and natural asphalt，rigid resin and elastic graphite were introduced. By investigating the plugging，temperature resistance and lubricity of the drilling fluid system，the adaptability evaluation of biomass synthetic base drilling fluid and formation was carried out. The results showed that the drilling fluid system had a temperature resistance of 180 ℃，a high temperature and high pressure filter loss of ≤ 5 mL，and a emulsion-breaking voltage of ≥ 700 V. The shale core of the Shahejie Formation had a rolling recovery rate of 98.32% in the biomass-based fluid for 16 h and a linear expansion rate of 0.817 % for 72 h. The drilling fluid system had been successfully applied in 9 wells on site，showing strong long-term stability against high temperature，low viscosity and high shear flow pattern，good rock carrying and sand carrying capacity，rock carrying index ＞ 1.5，and the highest application temperature of 156 ℃，which effectively solves the problems of wellbore instability， difficult rock carrying and sand carrying in long horizontal section，and directional back pressure of thin layer in Shahejie formation，and had good application and promotion prospects.

• Environmentally Friendly High-performance Water-based Drilling Fluid System Suitable for Deep Tight Oil Horizontal Wells

  CHEN Li, JIN Kai, LIAO Gan, FAN Yecan, HE Yihui, FENG Jun

  2026,43(1):8-17, DOI: 10.19346/j.cnki.1000-4092.2026.01.002

  Abstract: (97) HTML (0) PDF (0.00 ByteKB)(0)

  Abstract:

  In response to the difficulty of balancing environmental performance and temperature and salt resistance with traditional water-based drilling fluids，and taking into account the characteristics of deep tight oil horizontal well drilling，a set of environmentally friendly high-performance water-based drilling fluid system suitable for deep tight oil horizontal well drilling was developed based on the synthesized environmentally friendly temperature and salt resistant filtrate reducer SLP-2 and other environmentally friendly treatment agents，through the optimization of SLP-2 dosage and the selection of inhibitors and lubricants. The basic performance，settling stability，anti-pollution performance，reservoir protection performance，and environmental performance of the drilling fluid system were evaluated. The results showed that the system had outstanding temperature resistance performance. After aging at 180 ℃ for 16 h，the high temperature and high pressure filtration loss was controlled within 10 mL， which could meet the requirements of deep well operations. The system had strong inhibitory properties，with a rock debris rolling recovery rate of over 95%，which could effectively suppress formation mud making and wellbore collapse. The density control of the system was flexible and the settlement stability was strong. When the density reached up to 2.0 g/cm³，the density difference of the system was less than 0.2 g/cm³ and the settlement factor was less than 0.52. The lubrication performance of the system was excellent，and the lubrication coefficient was as low as 0.087，which could significantly reduce the wear and friction of the drilling tool. The system had strong anti- pollution ability. After adding pollutants such as 15% NaCl，1.0% CaCl₂，or 15% rock debris powder，the rheological parameters and filtration performance of the system remained stable. The environmental advantages of the system were obvious，the biotoxicity test showed that the EC50 value reached up to 75 600 mg/L（non-toxic level），and BOD5/COD ratio was 26.8%（easily biodegradable），and heavy metal content met industry environmental standards. This environmentally friendly high-performance water-based drilling fluid had been successfully applied in the CH-1 well，a deep tight oil-water horizontal well in the target block. The on-site operation results showed that there had been no complex accidents such as drill jamming or leakage during drilling. The performance of the drilling fluid was stable and controllable throughout the process，and the environmental indicators met the standards，achieving the goals of safe，efficient，and green drilling. It provides technical support for the drilling construction of deep tight oil-water horizontal wells and has good prospects for promotion and application.

• Evaluation of Emulsion Stability of Biomass Synthetic-based Drilling Fluids Using Multiple Light Scattering

  ZHANG Yi, SHAN Haixia, ZHAO Tiantian, WEI Hua, ZHOU Qicheng

  2026,43(1):18-26, DOI: 10.19346/j.cnki.1000-4092.2026.01.003

  Abstract: (36) HTML (0) PDF (0.00 ByteKB)(0)

  Abstract:

  Emulsion stability is a key parameter for oil-based and synthetic-based drilling fluids. To deeply investigate its stability mechanism and optimize formulations，the multiple light scattering method was utilized to systematically examine the effects of emulsifier type，organoclay concentration，emulsifier concentration，calcium chloride concentration，and oil-to-water ratio on the dynamic stability of a biomass synthetic-based drilling fluid. By combining multiple light scattering with electrical stability（ES） tests，the influence of each factor on emulsion stability was determined. The results showed that the emulsifier SWRH demonstrated optimal stabilizing effects due to its excellent compatibility with the LAE-12 base fluid. The emulsion exhibited better stability，was characterized by a lower turbiscan stability index （TSI） value and smaller particle size，under the following conditions：an organoclay concentration of 2.0%，an emulsifier concentration of 6%，a calcium chloride concentration of 40%，and an oil-to-water ratio no lower than 75∶25. The study also found that while the electrical stability test is convenient，it cannot comprehensively reflect the dynamic stability of the emulsion or the influence of complex factors. In contrast，the multiple light scattering method can more intuitively reveal instability mechanisms such as creaming and coalescence. The findings of this research provide a theoretical basis for the formulation optimization of biomass synthetic-based drilling fluids. It is proposed that combining multiple light scattering with electrical stability tests can establish a more comprehensive evaluation system for emulsion stability，offering theoretical support for the development and iterative improvement of high-performance biomass synthetic-based drilling fluids.

• Synthesis and Performance Evaluation of a High Temperature Viscosity Reducer

  ZHOU Xinyu, LI Huaike, LAI Quanyong

  2026,43(1):27-35, DOI: 10.19346/j.cnki.1000-4092.2026.01.004

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  Abstract:

  The rheological control of drilling fluids under high-temperature conditions at the bottom of deep wells remains a challenging issue. Viscosity reducers are considered as effective agents for adjusting the rheological properties of drilling fluids. However， the research on anti-high-temperature viscosity reducers is relatively limited in China. In this paper， an anti-high-temperature viscosity reducer named GMZ was synthesized，and its characterization，performance evaluation and mechanism analysis were carried out in order to provide a more reliable，efficient and environmentally friendly drilling fluid viscosity reducer product for domestic drilling operations. The results of FT-IR and 1H-NMR showed that glycerol，zirconium salt THSZ and polymaleic acid PMA reacted to obtain the target product GMZ. The results of thermogravimetric analysis showed that the thermal stability of GMZ was good，and the mass retention rate was as high as 45.57% at the end of high temperature burning. The results of performance evaluation experiments showed that GMZ could resist to high temperature of 210 ℃，and the viscosity reduction rate in the base slurry was as high as 82.61%. GMZ had good compatibility，and had good high temperature viscosity reduction and shear reduction effects in both sulfonation system and desulfonation system. Biological toxicity test indicated that the bioligical toxicity value of GMZ exceeded 40 000 mg/L，which satisfied the national standard for biological toxicity in water-based drilling fluids used in first-class marine areas. Particle size and Zeta potential analyses showed that the addition of 2% GMZ significantly reduced both the particle size and zeta potential of bentonite slurries after high-temperature aging at 210 ℃，indicating enhanced dispersion and mitigation of high-temperature-induced particle aggregation. Optical microscopy and SEM further confirmed that GMZ improved the dispersion of bentonite particles. XRD and TEM analysis revealed that the cations of GMZ replaced aluminum ions at the edges of clay layers，increasing intermolecular repulsion and contributing to its high-temperature resistance and viscosity-reducing effects. GMZ had already achieved industrial-scale production and showed promising application potential. However，its performance under high-temperature and high-density field conditions required further validation through actual field operations.

• Efficacy and Mechanism of Inorganic Bitumen Curing Agents in Canadian Oil Sands Drilling

  YANG Jie, HE Ping, GENG Tie, FAN Jing, DU Weichao

  2026,43(1):36-44, DOI: 10.19346/j.cnki.1000-4092.2026.01.005

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  Abstract:

  In drilling operations of Canadian oil sands，the problem of reduced operational efficiency caused by asphalt adhering to drilling components is urgent to be addressed. However，this issue is rarely encountered domestically，and there are no effective so-lutions or relevant evaluation schemes to draw upon，making the research extremely challenging. This paper focused on asphalt cur-ing technology，drew on the mechanism of inorganic curing agents releasing active oxygen atoms at high temperatures to recon-struct oil sand components. For the first time，asphalt penetration was introduced as the main performance indicator in this study. Six typical commercially available inorganic curing agents were selected and hot-rolled with Canadian oil sands in aging tanks. The penetration of oil sands before and after curing，the adhesion of simulated steel rods，and the influence of drilling fluid performance were investigated. The results indicated that the inorganic curing agent sodium thiosulfate，anhydrous sodium acetate and potassium persulfate showed significant curing efficiency，which reduced the penetration value of asphalt from 108/0.1 mm to 25.89/0.1 mm and had long-term stability. Among them，the sodium thiosulfate system showed the best inhibition effect in the adhesion test of steel rods，and the adhesion rate of asphalt decreased significantly from 50.93% to 6.71%. Furthermore，the solidification of oil sands had little effect on the rheology of the drilling fluid system，but it would cause negative effects such as increased filter loss and simulated drilling tool corrosion. Through Fourier transform infrared spectroscopy analysis，it was found that the active ions in the curing agent，such as CH₃COO^-，SO₄^2-，had a chemical crosslinking reaction with the polar functional groups in the asphalt， such as —OH，—COOH. Four-component analysis found that the curing agent promoted the conversion of saturated hydrocarbons and aromatic hydrocarbons with low molecular weight in the asphalt component to resins and asphaltenes with high molecular weight. The results of scanning electron microscopy and polarizing optical microscopy further confirmed that the microstructure of the solidified asphalt formed a porous network skeleton，resulting in an increase in the porosity of the filter cake，furtherly aggravat-ed the increase in drilling fluid loss. This study reveals the action mechanism of inorganic curing agent and oil sand asphalt for the first time，and provides a theoretical basis for solving the adhesion problem of oil sand drilling.

• Influence Law and Mechanism of Nano-SiO₂ Morphology on Properties of Oil Well Cement under Vapor Phase CO₂ Corrosion

  CUI Xiyue, TAN Huijing, WEI Jijun, XIE Lanlan, WANG Sheng, CHEN Yao, ZHENG Yuntian

  2026,43(1):45-53, DOI: 10.19346/j.cnki.1000-4092.2026.01.006

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  Abstract:

  Under high temperature and high-pressure water-containing gas-phase CO₂ environments，conventional silicate cements are susceptible to corrosion by acidic environments，which results in strength decline and structural deterioration. Mixing nano-SiO₂ in cement can reduce the Ca/Si ratio and permeability，thus improving the material's resistance to high temperature and corrosion. Nano-silica particles（NS）and sol-gel（SS）as the most common types of nano-SiO₂，but the application of the two materials in the cement paste has its own advantages and disadvantages. In this paper，based on the high-temperature and high-pressure vapor-phase CO₂ corrosion experiments，the compressive strength，XRD，FTIR and SEM tests were carried out to investigate the influence laws of different types of nano-SiO₂ on the mechanical strength，types of corrosion products and hydration products，and microstructures of the cement stone. The results showed that the compressive strength of cementite increased by 1.82%，9.1% and 15% sequentially at 150 ℃ with 1%，2% and 3% NS，while it decreased by 7.73%，4.09% and 2.73% with 1%，2% and 3% SS，respectively. Compared to the oil well cement，the Ca/Si ratio of C-S-H gel in the hydration product was reduced by 33.23% and 24.37%，and the Ca（OH）₂ content was reduced after mixing 3% NS and 3% SS，respectively. The addition of NS made the diffraction peak intensity of the hydration product Ca（OH）₂（001）crystal plane decrease obviously，and improved the crystal orientation of Ca （OH）2. The decline rate of the cement compressive strength was reduced by 10.35 percentage point and 10.98 percentage point，and the corrosion products CaCO₃ were reduced，the cement particles were more strongly cemented，and the corrosion resistance of cement stone was improved. Comprehensive comparing the mechanical strength and microstructure of cement stone before and after corrosion，NS had better effect on improving the high temperature resistance and corrosion resistance of cement stone than SS.

• Plugging Performance and Prediction Model of Liquid Colloidal Plug for Casing Deformation Wells in Luzhou Area，Southern Sichuan Basin

  LIU Xiangkang, WANG Xueqiang, SHI Yishuai, LU Linfeng, XU Bo, SONG Yi, XU Yi, SUN Dalong, YANG Yang

  2026,43(1):54-62, DOI: 10.19346/j.cnki.1000-4092.2026.01.007

  Abstract: (55) HTML (0) PDF (0.00 ByteKB)(0)

  Abstract:

  To address the problem that the conventional mechanical bridge plugs are difficult to set and hydraulic fracturing operations are constrained under casing deformation conditions in shale gas horizontal wells in the Luzhou area of southern Sichuan，this study aims to clarify the sealing pressure-bearing capacity and engineering applicability of liquid gel plugs in deformed casing. A liquid gel plug system composed of functionally modified polyacrylamide（TSRP）and polyethyleneimine （PEI）was investigated. Through rheological and gelation performance evaluation，combined with field-derived real deformed casing samples，a sealing pressure-bearing test platform was established. Systematic pressure-bearing experiments were conducted under different casing deformation types，deformation section lengths，filling degrees，and combinations of multiple deformation types，and a prediction model for sealing pressure-bearing capacity was developed. The results showed that before gelation，the liquid gel plug exhibited an apparent viscosity of 204 mPa·s under downhole shear conditions，demonstrating pronounced shear-thinning behavior and good pumpability. At 90 ℃，gelation began after 2—3 h and was completed within 3—4 h，with the final gel strength of grade I. Pressure-bearing tests indicated that in A-，B-，and C-type deformed casing sections，the maximum sealing pressure-bearing capacities of the liquid gel plug in deformation lengths of 1，3，and 5 m were 0.57—2.06 MPa，0.77—2.50 MPa，and 0.98—3.83 MPa，respectively，showing a significant increase with increasing sealing length and deformation severity. In C-type deformed casing，when the filling degree increased from 0.1 to 1.0，the sealing pressure-bearing capacity rose from 0.15 MPa to 2.54 MPa. Under a fixed total casing length，when the deformation section length was reduced from 3 m to 0.6 m，the sealing pressure-bearing capacity was increased from 2.54 MPa to 3.20 MPa. Among multiple deformation combinations，the A-type and C-type combination exhibited the highest sealing pressure-bearing capacity，reaching up to 4.31 MPa. Based on the experimental results of liquid gel plug sealing performance，a sealing pressure-bearing prediction model was established using grey relational analysis，providing guidance for field applications.

• Development and Performance Evaluation of Silica Sludge Ceramsite Plugging Agent

  LI Jixiang, ZHONG Liguo, NING Binyu, GAO Renfei, ZHANG Yong, SHI Xiaofeng, WANG Ge

  2026,43(1):63-69, DOI: 10.19346/j.cnki.1000-4092.2026.01.008

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  Abstract:

  Aiming at the problems of difficult treatment of silicon sludge produced during silicon removal from steam injection thermal recovery sewage in Liaohe oilfield，and formation deficit and inter-well steam channeling in the later stage of heavy oil steam injection development，a kind of temperature-resistant and high-strength silicon sludge ceramsite was prepared by granulation and sintering treatment with waste silicon mud as raw material，and prepared with polymer solution to obtain silicon sludge ceramsite plugging agent. The effects of silica sludge content and sintering temperature on the compressive strength and apparent density of silica sludge ceramsite were investigated through single factor experiments，and the hydrothermal stability，suspension and blocking properties of the plugging agent were evaluated. The results showed that the apparent density of silica sludge ceramsite was＞ 2.25 g/cm³，the compressive strength of silica sludge ceramsite was ＞14 MPa and the temperature resistance was 350 ℃under the conditions of 60% silica sludge doping and 1180℃ sintering temperature. The settlement rate of silica sludge ceramsite in the polymer solution with a mass fraction of 0.3%—0.5% was lessthan 0.0075 m/min，and the high temperature plugging rate was higher than 82%，which could meet the performance requirements of plugging，channeling and filling formation deficit in heavy oil thermal oil reservoirs in Liaohe oilfield. At the same time，the discharge of pollutants from silicon sludge in oilfield could be reduced by preparing ceramsite from silicon sludge produced by silicon removal from produced sewage and reusing in oilfield.

• Performance Evaluation of Quantum Dot Oil Displacement Agents and Macroscopic and Microscopic Oil Displacement Characteristics

  CAO Xiaoyi, LUO Xiangrong, LU Xiaobing, YAN Ruoqin, REN Xiaojuan, CHENG Feng, YANG Li’an, WANG Lei, CHEN Beier

  2026,43(1):70-77, DOI: 10.19346/j.cnki.1000-4092.2026.01.009

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  Abstract:

  In order to clarify the basic properties of the novel C-Si quantum dots and their applicability in low-ultra-low permeability reservoirs，the interfacial properties and compatibility of the C-Si quantum dot oil displacement agent were tested and analyzed. Subsequently，the core imbibition and displacement experiments were carried out to explore the macroscopic imbibition and displacement characteristics of quantum dots. Finally，the oil displacement characteristics of quantum dots were revealed from the microscopic level by means of nuclear magnetic resonance analysis and microscopic model experiments. The results showed that the quantum dot oil-displacement agent had the ability to change the core surface to hydrophilicity，meanwhile，it exhibited strong negative charge，as well as good temperature and salt resistance. When the concentration of the quantum dot oil-displacement agent was 0.5%，the imbibition oil-displacement effect was the best，and the imbibition efficiency reached as high as 48.5%，showing a continuous effect during the core displacement process. The particle size of quantum dots was small，so the Brownian motion of quantum dots was more intense，and the quantum dots easily entered the micro-pores. The imbibition efficiency of the quantum dots in the micro-pores of the core could reach up to 30%. The quantum dots expanded the sweep range of the water phase by weakening the hydrogen-bond association of water molecules，and could effectively activate bypassed residual oil，dead-end and corner residual oil. The research results lay a theoretical foundation for improving the oil recovery of low and ultra-low permeability reservoirs using the quantum dot oil-displacement agent.

• Role of Temperature-resistant Multifunctional Polymer-enhanced Hot Water Flooding in Improving Offshore Heavy Oil Recovery

  LIANG Dan, ZHANG Jian, ZHOU Wensheng, HUA Zhao, ZHANG Qichen, LIU Zhenkun

  2026,43(1):78-89, DOI: 10.19346/j.cnki.1000-4092.2026.01.010

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  Abstract:

  In view of the technical problems faced by high-temperature thermal recovery technology for offshore heavy oil，such as high cost，high risk，and the limited oil-increasing effect of single hot-water flooding，a synergistic hot-water flooding technology based on self-developed temperature-resistant multifunctional polymers TMP was systematically evaluated to clarify its mechanism of enhancing oil recovery and its potential for field application. A research approach integrating laboratory experiments and numerical simulations was employed and the performance of polymer TMP in viscosity enhancement of water，viscosity reduction of oil，interfacial tension reduction，and the disassembly of asphaltene aggregates was systematically evaluated. Using the CMG numerical simulation software，an injection-production well pattern model was established，the displacement process was inversed， and the impacts of static and dynamic reservoir factors on the oil-increasing effect were investigated. The experimental results indicated that at 80 ℃ and a concentration of 1500 mg/L，the solution viscosity of the polymer was approximately 80 mPa s，and it exhibited excellent temperature resistance. It could reduce the oil-water interfacial tension to the order of 10^-1 mN/m. By disassembling asphaltene aggregates，the viscosity reduction rate of crude oil could reach 85% at 80 ℃. The numerical simulation results showed that the enhanced oil recovery rate of polymer-enhanced hot-water flooding could reach 6.0 percentage point，which was significantly higher than that of single hot-water flooding（1 percentage point—2 percentage point）. As for the oil-increasing effect，the polymer played a dominant role with a contribution rate of 80%—90%，while thermal energy played an auxiliary and synergistic role with a contribution rate of 10%—20%. The study determined that the optimal reservoir conditions suitable for this technology were as follows：average permeability＞2000×10^-3 μm²，in-situ crude oil viscosity of 200—600 mPa s，and water-body multiple＜4. The temperature-resistant multifunctional polymer-enhanced hot-water flooding technology， achieved the complementary advantages of "relying mainly on thermal energy to reduce viscosity near the well and chemical energy to reduce viscosity in deep formations" through the synergy of thermal energy and chemical energy，and had the dual effects of expanding the swept volume and improving the oil-washing efficiency. The project design for the Bohai D oilfield demonstrated that this technology could increase the oil recovery rate by 5.9 percentage point compared to water flooding，providing a promising new approach for the economic and efficient development of offshore heavy oil.

• Construction and Viscoelastic Characterization of Wormlike Micellar Foam Systems for CO₂ Flooding

  WU Yuhui, PEI Haihua, ZHANG Guicai, LIU Yang, MA Zhanlei, DAI Wangdong

  2026,43(1):90-97, DOI: 10.19346/j.cnki.1000-4092.2026.01.011

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  Abstract:

  Gas channeling during CO₂ flooding often reduces sweep efficiency and oil recovery. It is proven that foam injection was effective in controlling CO₂ breakthrough. A wormlike micellar foam system was developed using anionic surfactant sodium α-olefin sulfonate（AOS），zwitterionic surfactant erucic acid amide propyl betaine（EAB），and foam stabilizer alkylamine（TA），and its viscoelastic behavior was systematically investigated. The experimental results showed that the comprehensive index of the foam system with the formula of 0.25% AOS + 0.25% EAB + 0.1% TA could reach 107 208 mL· min. While the foam performance decreased with rising temperature，the system maintained good stability below the temperature of 70 ℃. Viscoelastic analysis revealed that at 0.5% total surfactant concentration，AOS and EAB molecules intertwined to form abundant wormlike micelles，as a result，the bulk viscosity and viscoelasticity of the system was significantly improved. The high viscoelasticity of the wormlike micelle structure could effectively retard the liquid film drainage and enhance the strength of the foam liquid film，and thereby improve the foam stability.

• Preparation and Performance Evaluation of Low Interfacial Tension Anti-high Calcium and Magnesium Oxygen-reducing Air Foam System

  CHEN Longlong, NI Jun, WEI Dengfeng, TANG Ruijia, SHANG Qinghua, MA Bin

  2026,43(1):98-105, DOI: 10.19346/j.cnki.1000-4092.2026.01.012

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  Abstract:

  In response to the poor water flooding effect，high water cut（≥75%），low recovery rate（14.7%），in the Chang 6 tight oil reservoir of the Yanchang oilfield，which is characterized by high salinity formation water（≥120 000 mg/L），high calcium and magnesium（Ca²⁺ content≥20 000 mg/L，Mg²⁺ content≥400 mg/L），and strong heterogeneity（permeability contrast =50），and the current foam systems' inability to adapt to these conditions，eight Gemini surfactants were evaluated for their foaming performance， half-life，and comprehensive foam index under simulated reservoir conditions using a high-temperature and high-pressure foam instrument and a tight reservoir imbibition system. The best foaming agent，auxiliary agent，and their concentrations were optimized to construct a low interfacial tension，calcium and magnesium resistant，and oxygen-reduced air foam system. The effects of different temperatures，Ca²⁺ and Mg²⁺ contents，oil saturation，and pH values on the foaming volume and half-life of the system were evaluated，and the oil displacement efficiency and imbibition efficiency of the system in heterogeneous reservoirs were investigated. The results showed that 0.4% LY-12（dodecyldodecyl hydroxysulfonate）+ 0.1% LX-14（tetradecyl amino acid salt） was the best foam system. Temperature，Ca2 + content，oil content，and pH had a significant impact on the foaming volume and foam half-life，while the effect of Mg2 + content was relatively small. The best foam performance could be guaranteed under conditions of temperature ≤45 ℃，Ca²⁺ content ≤20 000 mg/L，oil content ≤ 30%，and neutral pH，with a comprehensive foam index ≥12 000 mL min and an interfacial tension of 6.63×10^-2 mN/m. When the permeability contrast was 50，the continuous foam flooding in heterogeneous reservoirs had a 7% higher comprehensive oil displacement efficiency than the foam slug followed by water flooding. When the permeability was 0.96×10^-3 μm²，the imbibition efficiency reached up to 42.88%，demonstrating good adaptability to low-permeability reservoirs.

• Performance Evaluation of High-temperature High-salinity Resistant Foam-assisted Gas Flooding for Fractured-vuggy Reservoirs

  SONG Zhengcong, HAN Guoqing, ZHAO Yajie

  2026,43(1):106-114, DOI: 10.19346/j.cnki.1000-4092.2026.01.013

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  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. In this paper，the adaptability evaluation of high temperature and high salinity resistant foam-assisted gas flooding technology in this kind of reservoir was carried out through the optimization of foam system，the physical model oil displacement simulation experiment of weathering crust and the field pilot test. The results showed that the temperature-resistant and salt-resistant foam system TKQP-3，composed of 0.12 % anionic-nonionic surfactant SS-163 + 0.18% anionic surfactant AES + 0.2% foam stabilizer SAV-236，could stably adapt to the harsh reservoir environment with temperature of 120 ℃，salinity of 24×10⁴ mg/L and pressure of 30 MPa. The foaming volume was 4 times that of the base fluid，and the half-life of the foam was about 30 min. The foam retention rate after cutting adsorption was still as high as 97%. At 120 ℃，the resistance factor of the foam system was more than 40 when the gas-liquid ratio was 1.5∶1 in a simple fracture-cavity sand-filled tube model with a liquid phase permeability of about 1500 × 10^-3 μm². Indoor physical simulation experiments had confirmed that the system could effectively expand the swept volume and increase the recovery rate by an average of more than 10 percentage points through the mechanisms of regulating flow steering，improving the oil-gas mobility ratio，promoting foam-gas-water three-phase synergy and reducing interfacial tension. The field test further verified its application effect，and the cumulative oil increase of the A71 well group reached up to10 373 t. In summary，the foam-assisted gas flooding technology has shown good adaptability and development potential in Tahe fractured-vuggy reservoirs.

• Reservoir Adaptability and Oil Displacement Potential Evaluation of Microemulsion Systems in Low-permeability Reservoirs

  LI Jialu, LIU Yunlong, YAN Ning, WANG Teng, LYU Dongfang, ZHAO Wenjing, CHEN Jia, ZHAO Guang

  2026,43(1):115-124, DOI: 10.19346/j.cnki.1000-4092.2026.01.014

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  Abstract:

  Microemulsion exhibits significant application potential in low-permeability reservoirs owing to its superior capabilities in reducing oil-water interfacial tension，altering wettability，enhancing solubilization，and maintaining thermal stability. Taking the low permeability reservoir in Block Chang-3 of Changqing oilfield as an example，the reservoir adaptability of the field application of microemulsion system was systematically evaluated by means of microemulsion micromorphology measurement， particle size analysis，interfacial tension measurement，crude oil component solubilization and wettability test，and its oil displacement potential was explored by means of nuclear magnetic resonance online displacement system. The experimental results demonstrated that the microemulsion exhibited an oil-in-water（O/W）structure with an average particle size of approximately 13 nm，which could effectively match with the micro-nano pore throat of low permeability reservoir. Notably，this system achieved significant interfacial activity，reducing oil-water interfacial tension to 1.71 mN/m，while the interfacial modulus increased with rising oscillation frequency. After 20 days of aging at the reservoir temperature，the key parameters including particle size and interfacial tension kept stable，while the microemulsion demonstrated exceptional solubilization capacity with an oil solubilization parameter reaching 36 mL/g，particularly，the enhanced solubilization effects were observed for saturated and aromatic fractions. Furthermore，the system effectively altered reservoir wettability，as evidenced by the substantial decrease in underwater oil droplet contact angle from 164° to 55° ，indicating a successful transition from oil-wet to water-wet conditions. The nuclear magnetic resonance online flooding experiments further revealed that injection of 1.0 PV of the microemulsion enhances oil recovery by 10.86 percentage point while reduced displacement pressure by 24.87% ，demonstrating significant pressure reducing and injection enhancing effects. The experimental results revealed that the microemulsion system exhibited considerable potential for enhanced oil recovery，providing crucial technical support for its large-scale field application in low-permeability reservoirs of Changqing oilfield.

• Effect of Sodium Silicate on Salt Tolerance of Polymers in High Salinity Reservoirs

  LIU Zilong, LU Xiangguo, HE Xin, LIU Jinxiang, GAO Jianchong

  2026,43(1):125-130, DOI: 10.19346/j.cnki.1000-4092.2026.01.015

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

  Abstract:

  The Bohai high-salinity reservoir exhibits relatively high average permeability，while the salt tolerance of ordinary polymers is poor. In order to enhance the salt tolerance of conventional polymers and improve the oil-increasing and water-reducing effects of flooding agents，the effect of sodium silicate on salt tolerance of polymer in high salt reservoir and its mechanism were studied by viscosity and scanning electron microscope test combined with physical simulation evaluation method. The results indicated that the viscosity of the ordinary polymer solution with a mass concentration of 2000 mg/L was 12.4 mPa s lower than that of the salt-resistant polymer solution（32.5 mPa s）under the condition of salinity of 10 206.6 mg/L. Adding sodium silicate to the ordinary polymer solution could increase the viscosity of the system. As the concentration of sodium silicate increased，the viscosity of the 'ordinary polymer + sodium silicate' composite system gradually increased. In different dosing methods，the viscosity of the initial' polymer（2000 mg/L）+ sodium silicate（ 500 mg/L）' system（16.8 mPa·s ）was lower than that of the 'sodium silicate + polymer' composite system（19.6 mPa·s）. However，their viscosities show little difference after shearing. Polymer molecules formed a network structure，while the inorganic gels exhibited a flocculent structure. The "polymer + sodium silicate" system resulted in a denser network framework. With the increase of sodium silicate concentration，the resistance coefficient of the composite system increased，and the residual resistance coefficient increased first and then decreased. The plugging rate of the ordinary polymer system（2000 mg/L）to the core with a permeability of about 6000×10^-3 μm² was only 20%，while the plugging rate of the 'polymer（2000 mg/L）+ sodium silicate（300 mg/L）' composite system to the core with a permeability of about 6000× 10^-3 μm² was as high as 94.3%.

• Developed Limit and Oil Displacing Characteristics of Heterogeneous Combination Flooding after Surfactant-polymer Flooding

  PAN Binlin, SHI Jing, ZHAO Fangjian, JIANG Zuming

  2026,43(1):131-138, DOI: 10.19346/j.cnki.1000-4092.2026.01.016

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

  Abstract:

  The residual oil distribuion becomes complex after surfactant-polymer flooding （SP flooding）. Heterogeneous combination flooding（HC flooding）has the dual functions of profile control and oil displacement，therefore it can be used to employ the residual oil after SP flooding. In this paper，the developed limit of the residual oil at various pore throats was studied by NMR using different-permeability cores，and the CT scanning of the residual oil in the heterogeneous square cores with different permeability ratios through the heterogeneous composite flooding after SP binary composite flooding was carried out. The experimental results showed that the effective producing limitation for residual oil under HC flooding was 0.3—20 μm for the cores with permeability of 1 μm² and 0.2—800 μm for the cores with permeability of 6 μm². CT scanning of heterogeneous cubic cores with different permeabilities showed that the injectivity of viscoelastic particles（PPG）had significant influence on the enhanced oil recovery of the low-permeability zone. If the particle size was compatible with the pore-throat size of the low-permeability zone， the residual oil in the low-permeability zone could be effectively developed by HC flooding，resulting in the enhanced oil recovery by 18.3 percentage point. When the compatibility was poor，the residual oil only in the injection part could be displaced by HC flooding，the performance of profile control and oil displacement of HC flooding was limited and the enhanced recovery rate was only 9.5 percentage point.

• Evaluation on Foam Stabilization Performance of Novel Temperature- and Salt-resistant Terpolymer and Molecular Dynamics Simulation to Elucidate the Mechanism

  DAI Yuting, LI Mei, GAO Pengchao, LI Danchen, GAO Qi, XU Xingguang, ZHANG Lei

  2026,43(1):139-146, DOI: 10.19346/j.cnki.1000-4092.2026.01.017

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

  Abstract:

  To overcome the poor stability of CO₂ foam under high-temperature and high-salinity conditions，sodium α-olefin sulfonate（AOS，anionic）and octylphenol polyoxyethylene ether（OP-40，nonionic）were formulated as a mixed foaming agent， and a temperature- and salt-tolerant terpolymer（AMPA）was introduced as the foam stabilizer. The optimal composition（surfactant concentration and AOS/OP-40 mass ratio）was screened using the Waring-blender method. Foam performance was then evaluated at 80 ℃ and 100 000 mg/L salinity and benchmarked against a conventional HPAM-stabilized system. In parallel，molecular dynamics（MD）simulations were conducted by constructing a gas/liquid interfacial model to elucidate the interfacial synergy between the anionic-nonionic surfactant mixture and AMPA，and to rationalize the performance differences between AMPA and HPAM in modifying the interfacial properties. When the mass ratio of AOS to OP-40 being of 1∶1，total surfactant content being of 1.0%，and AMPA dosage being of 0.35%，the optimized AMPA-stabilized foam system achieved a foam volume of 420 mL and a drainage half-life of 35.6 min. Under the same harsh conditions，the drainage half-life of the AMPA system was 2.3 times that of the HPAM-stabilized foam. MD simulations revealed that AMPA exhibited stronger synergistic interactions with surfactants，resulting in thicker hydration and gas adsorption layers，reduced liquid film drainage rate and delayed gas diffusion. Additionally，AMPA significantly decreased interfacial tension and formation energy，leading to more stable interfaces and stronger foam stability. These findings provide a theoretical foundation for the molecular design of next-generation foam stabilizers.

• Permeability Enhancement Characteristics of Nanobubble-SiO₂ Composite Nanofluid System in Tight Reservoir

  QU Shiyuan, LI Huili, HUANG Bo, BAI Haoli, WANG Siqi, YE Zhilin

  2026,43(1):147-154, DOI: 10.19346/j.cnki.1000-4092.2026.01.018

  Abstract: (41) HTML (0) PDF (0.00 ByteKB)(0)

  Abstract:

  Imbibition is an important mechanism for enhancing oil recovery in tight reservoirs. Both nanoparticles and nanobubbles can penetrate nanoscale pores to modify oil-water properties. Furthermore，nanobubbles can additionally provide microscopic energy supplementation，making them ideal systems for permeability enhancement and recovery improvement in tight reservoirs. Taking core samples from the Chang-6 reservoir in Wuqi area as research subjects， this study investigated the permeability-enhancing characteristics of active nanofluid（nanobubbles + nano-SiO₂ particles）and simulated field application effects. The results showed that 0.1% active nanofluid enhanced core water wettability by 48.3% and reduced oil-water interfacial tension by 17.8%，which significantly decreased flow resistance and facilitated imbibition. Synergistic effects between nanoparticles and nanobubbles enhanced imbibition efficiency. The imbibition recovery of 0.1% active nanofluid was 5.47 percentage points higher than that of formation water and 2.37 percentage points superior to pure SiO₂ nanofluid. The effectiveness of the system containing nanobubbles increased by 1.76 times compared to pure nano-SiO₂ system. Differential pore mobilization mechanisms were observed between oil-wet and water-wet formations. Oil-wet reservoirs primarily mobilized crude oil from medium pores （27.8 nm＜r≤203.9 nm），while water-wet formations predominantly target large pores （r≥126.9 nm）. Simulation results indicated significant operational improvements within 3 years of active nanofluid injection，reducing water cut from 60% to 40%and achieving up to 150% daily production increase compared with non-enhanced recovery scenarios. Over a 6-year simulation period，the adjusted recovery factor surpassed conventional waterflooding by 15%. These findings provided valuable insights for imbibition recovery in tight and shale ultra-low permeability reservoirs.

• Seepage and Oil Displacement Characteristics of Temperature-resistant and Salt-tolerant Binary Composite Flooding System in Ultra-long Cores

  XU Hui, SUN Xiuzhi, GONG Jincheng, HAN Baofeng

  2026,43(1):155-164, DOI: 10.19346/j.cnki.1000-4092.2026.01.019

  Abstract: (27) HTML (0) PDF (0.00 ByteKB)(0)

  Abstract:

  The traditional research on the seepage characteristics of polymer flooding systems mostly adopts static adsorption method and small model method. The chromatographic separation phenomenon is not obvious，which cannot reflect the real seepage law of the reservoir. In order to study the real migration law of the new temperature-resistant and salt-tolerant binary flooding system in the Class Ⅲ reservoir of Shengli oilfield，a 10 m ultra-long sand-packed model was used to investigate the dynamic performance changes and long-distance migration of the binary system under the conditions of reservoir temperature of 90 ℃ and salinity of 58 002 mg/L. Meanwhile，the oil displacement efficiency and residual oil distribution of conventional binary and temperature-resistant salt-tolerant binary systems were studied. The research results showed that，with the increase of migration distance，the viscosity of the system gradually decreased，and the viscosity loss was greater in the early stage of injection. After a certain distance of migration，the viscosity loss gradually leveled off. With the increase of injection volume，the viscosity of the system showed a gradient distribution，and the peak of the viscosity curve continued to shift to the right. The oil displacement test results of conventional binary and temperature-resistant salt-tolerant binary systems showed that the 0.6 PV conventional binary flooding system enhanced oil recovery degree by 16.65 percentage point，while the 0.6 PV temperature-resistant salt-tolerant binary flooding system enhanced oil recovery by 21.72 percentage point，which was 5.07 percentage points higher than the former，and 4.41 percentage points higher in the 0.6 PV stage of chemical flooding. The residual oil distribution test results showed that the startup effect of residual oil in the near-well zone（0—2 m）was good；in the middle（3.33—7.33 m）of the model，the residual oil saturation of temperature-resistant salt-tolerant binary flooding increased slightly；while in the deep part（7.33—10 m）of the model，due to the serious loss of system performance，the residual oil saturation was significantly higher. From the perspective of residual oil saturation after oil displacement by the two systems，the temperature-resistant salt-tolerant binary system had better overall propulsion performance and mobility control ability；the injection of flooding system with large slug in homogeneous reservoir was more conducive to enhancing oil recovery.

• Solution Properties and Oil Displacement of a Novel Microbial Polymer

  LI Caifeng, CAO Yanbin, LIU Tao, YAN Yitian, WANG Weidong, SONG Yongting, CHEN Qiongyao

  2026,43(1):165-172, DOI: 10.19346/j.cnki.1000-4092.2026.01.020

  Abstract: (35) HTML (0) PDF (0.00 ByteKB)(0)

  Abstract:

  Conventional synthetic polymer HPAM and xanthan gum exhibit poor temperature and salt tolerance，being prone to degradation and viscosity loss under high-temperature（≥80℃）and high-salinity（≥30 000 mg/L）conditions，and the residual monomer of HPAM is easy to pollute the environment，which is difficult to meet the development needs of high temperature and high salt reservoirs. To address the demands of harsh reservoir conditions，a new type of green and efficient microbial polymer FH had been developed. The effects of temperature，salinity，shear force and pH value on the rheological properties of FH polymer were investigated using a rheometer. The microstructure of FH polymer under different salinity was observed by scanning electron microscope，and the long-term thermal stability and oil displacement effect of FH polymer were evaluated. The experimental results showed that the viscosity of the FH solution，xanthan gum solution and polymer solution decreased sharply when they were sheared，and the higher the shear rate，the faster the viscosity decreased. When the shear force was eliminated，the viscosity of FH solution and xanthan gum solution became 109.3 mPa·s and 61.1 mPa·s，respectively，and the viscosity recovery rate was above 98%，indicating that the shear thinning phenomenon of the FH solution and xanthan gum solution was reversible and shear recovery was good. However，the viscosity of HPAM solution showed irreversible loss after shearing. Compared with xanthan gum，the FH polymer had a wide range of reservoir adaptability. The temperature resistance could be increased by more than 20 ℃，and the viscosity remained stable in both acidic and alkaline environments. Especially in the high salinity of formation water，the FH biopolymer could form a dense network structure，which enhanced its harsh environmental tolerance. In addition，under the treatment of high temperature and high salt for 40 days，the addition of sulfur-containing organic compound antioxidant could improve the thermal stability of FH biopolymer，and the viscosity retention reached 73.6% . In the physical simulation oil displacement experiment，the injection of the FH polymer system（50 g/L FH +0.2% antioxidant S）enhanced the oil recovery by 22 percentage points based on water flooding（oil recovery being about 44%），which demonstrated superior oil displacement performance and had broad application prospects under extreme reservoir conditions.

• Micro-oil Displacement Mechanism of Novel Microbial Polysaccharides Based on Microfluidics

  LIU Tao, HU Jing, SONG Yongting, YUE Shenghui, XIANG Yiwei, MA Mengqi, WANG Weidong, ZHANG Benhua, ZHU Guiping

  2026,43(1):173-180, DOI: 10.19346/j.cnki.1000-4092.2026.01.021

  Abstract: (31) HTML (0) PDF (0.00 ByteKB)(0)

  Abstract:

  This paper focused on a novel microbial polysaccharide as the research subject，using the high-temperature and high-salinity conditions in Shengli oilfield as the basis for experimental design. Based on the Micro-CT scanning results，the micro-channel pattern model was designed by QSGS technology，and the experimental microfluidic model was made by wet etching technology combined with surface modification method. The microbial polysaccharide micro-displacement experiments were conducted in high-temperature and high-salinity environments，and the overall images and microscopic phenomena at various displacement stages were captured，thereby the micro-oil displacement effectiveness of the polysaccharide system in high-temperature and high-salinity heavy oil reservoirs was evaluated. The study demonstrated that the novel microbial polysaccharide exhibited excellent temperature and salt resistance，maintaining high viscoelastic properties under reservoir conditions of 86 ℃ and salinity exceeding 45 939 mg/L，which was significantly improved compared with xanthan gum and met the requirements for injection agents in high-temperature and high-salinity reservoirs. Under the microscopic conditions，the novel polysaccharide could mobilize more clustered residual oil，which gradually transformed into porous residual oil and further into droplet-like residual oil during the displacement process，enhancing the displacement efficiency by 10.15 percentage point when injecting 0.5 PV of new microbial polysaccharide solution with viscosity of 95.6 mPa·s based on water flooding，which was 3.08 percentage point higher than that of xanthan gum. As a pure biological agent，the novel microbial polysaccharide shows promising temperature and salt resistance along with effective performance，indicating its potential application in high-temperature and high-salinity reservoirs and providing a viable technical approach for enhancing oil recovery in such environments.

• Research Progress on Metal-organic Framework Materials for Viscosity Reduction of Heavy Oil

  ZHAO Xiaoxiao, GE Minglan, WANG Jing, YANG Yuanliang, TAO Jianqiang

  2026,43(1):181-190, DOI: 10.19346/j.cnki.1000-4092.2026.01.022

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

  Abstract:

  Metal-organic Frameworks（MOFs）possess a high specific surface area，adjustable pore structures，and abundant active sites. These characteristics demonstrate their unique potential in the field of viscosity reduction of heavy oil. In The paper，the research progress of MOFs used in the field of heavy oil viscosity reduction was systematically reviewed. Firstly，the types and structural characteristics of MOFs，as well as the mechanism of heavy oil viscosity，were introduced; then，by analyzing the structural characteristics of MOFs and the structure-activity relationship between heavy oil components，the synergistic mechanism of MOFs in physical adsorption，catalytic cracking，and interface regulation was revealed. The mechanism of MOFs viscosity reduction was discussed in detail. Finally，prospects for the industrial application of MOFs were proposed，providing new ideas for the green development of oil fields under the“dual carbon”goal.

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

  ZHAO Kaiqiang

  Abstract: (612) HTML (0) PDF (0.00 ByteKB) (813)

  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: (609) HTML (0) PDF (0.00 ByteKB) (760)

  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: (658) HTML (0) PDF (0.00 ByteKB) (876)

  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: (563) HTML (0) PDF (0.00 ByteKB) (881)

  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: (934) HTML (0) PDF (0.00 ByteKB) (930)

  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: (826) HTML (0) PDF (0.00 ByteKB) (1435)

  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: (1215) HTML (0) PDF (0.00 ByteKB) (1484)

  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: (1170) HTML (0) PDF (0.00 ByteKB) (1327)

  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.

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

  LIU Jing, MA Cheng

  Abstract: (1084) HTML (0) PDF (0.00 ByteKB) (1657)

  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.

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

  MENG Wenyu, TANG Shanfa

  Abstract: (891) HTML (0) PDF (0.00 ByteKB) (1572)

  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

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

  WANG Wanfei, FU Hong

  Abstract: (913) HTML (0) PDF (0.00 ByteKB) (1593)

  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: (917) HTML (0) PDF (0.00 ByteKB) (1319)

  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.

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• Mechanical strength of polyacrylamide composite hydrogel reinforced by nanocrystalline cellulose

  MA Yanqi, LIN Meiqin

  Abstract: (1114) HTML (0) PDF (0.00 ByteKB) (1637)

  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: (1050) HTML (0) PDF (0.00 ByteKB) (1429)

  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.

  • 1
• Screening and evaluation of cheap nutrient system for sandstone reservoir in well block LQ, Xinjiang

  WANG Hongbo, MA Ting

  Abstract: (655) HTML (0) PDF (0.00 ByteKB) (1539)

  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.

  • 1
• Research progress of drag reducers for fracturing and its drag reduction mechanism

  SI Xiaodong, LI Mingzhong

  Abstract: (1916) HTML (0) PDF (0.00 ByteKB) (1904)

  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.

  • 1
• Effect of autogenous heat system on fracturing fluid gel breaking performance

  SHEN Xiulun

  Abstract: (1135) HTML (0) PDF (0.00 ByteKB) (2085)

  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: (859) HTML (0) PDF (0.00 ByteKB) (1606)

  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).

  • 1
• Optimization of synthesis conditions and evaluation of indoor oil displacement effect of a supercritical carbon dioxide thickener

  Fu Hong

  Abstract: (1085) HTML (0) PDF (0.00 ByteKB) (1272)

  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: (734) HTML (0) PDF (0.00 ByteKB) (1463)

  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.

  • 1
• PREPARATION OF HIGHLY POROUS NI-MO CATALYST BASED ON γ-AL₂O₃ AND ITS CATALYTIC EFFECT ON ULTRA-HEAVY OIL VISCOSITY REDUCTION

  Yuan Chengdong

  Abstract: (693) HTML (0) PDF (0.00 ByteKB) (1331)

  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.

  • 1
• Evaluation of inhibition effect of ionic liquid on asphaltene precipitation in crude oil under high temperature and pressure

  CAO Pengfu

  Abstract: (841) HTML (0) PDF (0.00 ByteKB) (1346)

  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: (730) HTML (0) PDF (0.00 ByteKB) (1337)

  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: (725) HTML (0) PDF (0.00 ByteKB) (1329)

  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: (819) HTML (0) PDF (0.00 ByteKB) (1490)

  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: (1010) HTML (0) PDF (0.00 ByteKB) (1456)

  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: (1003) HTML (0) PDF (0.00 ByteKB) (1360)

  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: (927) HTML (0) PDF (0.00 ByteKB) (1517)

  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: (895) HTML (0) PDF (0.00 ByteKB) (1468)

  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: (732) HTML (0) PDF (0.00 ByteKB) (1783)

  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: (675) HTML (0) PDF (0.00 ByteKB) (1470)

  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: (953) HTML (0) PDF (0.00 ByteKB) (1688)

  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: (650) HTML (0) PDF (0.00 ByteKB) (2211)

  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: (1073) HTML (0) PDF (0.00 ByteKB) (1441)

  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: (804) HTML (0) PDF (0.00 ByteKB) (1424)

  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: (750) HTML (0) PDF (0.00 ByteKB) (1389)

  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: (616) HTML (0) PDF (0.00 ByteKB) (1475)

  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: (1154) HTML (0) PDF (0.00 ByteKB) (1463)

  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: (770) HTML (0) PDF (0.00 ByteKB) (1369)

  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: (852) HTML (0) PDF (0.00 ByteKB) (1389)

  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: (747) HTML (0) PDF (0.00 ByteKB) (1427)

  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: (904) HTML (0) PDF (0.00 ByteKB) (2176)

  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: (927) HTML (0) PDF (0.00 ByteKB) (1595)

  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: (774) HTML (0) PDF (0.00 ByteKB) (1549)

  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: (675) HTML (0) PDF (0.00 ByteKB) (1784)

  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: (970) HTML (0) PDF (0.00 ByteKB) (1702)

  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: (786) HTML (0) PDF (0.00 ByteKB) (1475)

  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: (1560) HTML (0) PDF (0.00 ByteKB) (1588)

  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: (629) HTML (0) PDF (0.00 ByteKB) (1427)

  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".

  • 1
• Cationic Surfactant Pretreats Formation to Enhance Squeeze Life of Scale Inhibitor

  SONG Haojun, REN Shaoran

  Abstract: (617) HTML (0) PDF (0.00 ByteKB) (1474)

  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: (1013) HTML (0) PDF (0.00 ByteKB) (1465)

  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: (781) HTML (0) PDF (0.00 ByteKB) (1526)

  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: (725) HTML (0) PDF (0.00 ByteKB) (1534)

  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: (729) HTML (0) PDF (0.00 ByteKB) (1526)

  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: (1250) HTML (0) PDF (0.00 ByteKB) (1658)

  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.

  • 1
• Development and performance evaluation of high temperature-resistant core-shell nano plugging agent used for oil-based drilling fluid

  Du Zhenghong, Peng Wu

  Abstract: (1135) HTML (0) PDF (0.00 ByteKB) (1532)

  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: (898) HTML (0) PDF (0.00 ByteKB) (1591)

  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: (946) HTML (0) PDF (0.00 ByteKB) (1715)

  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.

  • 1
• Preparation and properties of gel dispersion for profile-controlling and flooding by aqueous RAFT polymerization

  YANG Ziteng, ZHANG Peng

  Abstract: (835) HTML (0) PDF (0.00 ByteKB) (1594)

  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: (943) HTML (0) PDF (0.00 ByteKB) (1798)

  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: (965) HTML (0) PDF (0.00 ByteKB) (1906)

  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: (831) HTML (0) PDF (0.00 ByteKB) (1572)

  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: (727) HTML (0) PDF (0.00 ByteKB) (1427)

  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: (1328) HTML (0) PDF (0.00 ByteKB) (1556)

  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: (719) HTML (0) PDF (0.00 ByteKB) (1462)

  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: (832) HTML (0) PDF (0.00 ByteKB) (1574)

  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: (1154) HTML (0) PDF (0.00 ByteKB) (1631)

  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.

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

  Li Yikun

  Abstract: (929) HTML (0) PDF (0.00 ByteKB) (1571)

  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: (1120) HTML (0) PDF (0.00 ByteKB) (1574)

  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.

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

  ZHANG Ying, YU Weichu

  Abstract: (1100) HTML (0) PDF (0.00 ByteKB) (1550)

  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: (970) HTML (0) PDF (0.00 ByteKB) (1535)

  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.

  • 1
• Research on Mechanism of Pickering Microemulsion Control Swelling of Clay in Heavy Oil Reservoir

  Guo MIngzhe

  Abstract: (932) HTML (0) PDF (0.00 ByteKB) (1486)

  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.

  • 1
• water-soluble resin-based cementing fluid system

  HE Yingzhuang, YAN Siming

  Abstract: (749) HTML (0) PDF (0.00 ByteKB) (1674)

  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: (797) HTML (0) PDF (0.00 ByteKB) (1644)

  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.

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

  SHEN Huibing, WU Pingping

  Abstract: (1013) HTML (0) PDF (0.00 ByteKB) (1623)

  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: (1039) HTML (0) PDF (0.00 ByteKB) (1670)

  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.

  • 1
• Efficient preparation of nano starch particles and its effect on the performance of drilling fluid

  Ma Peng, Zhang Lei

  Abstract: (1032) HTML (0) PDF (0.00 ByteKB) (1840)

  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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• Study and Application of Nanofluid Emulsion Flooding System for Enhanced Oil Recovery and Injection Capacity in Tight Oil Reservoirs

  LV Haifeng

  Abstract: (61) HTML (0) PDF (0.00 ByteKB) (0)

  Abstract:

  Tight oil reservoirs are characterized by fine pore throats and poor seepage capacity, where spontaneous imbibition serves as the core mechanism for enhancing oil recovery. However, conventional surfactant flooding systems suffer from issues such as high adsorption loss on rock surfaces and insufficient adaptability of interfacial properties, failing to meet the injection enhancement requirements of unconventional reservoirs and effectively strengthen spontaneous imbibition. In this study, a uniform and stable nano-emulsion system was prepared via a four-step process: "organic phase predispersion - aqueous phase activation - crosslinking coating - precise particle size control." The action mechanism of the system was revealed through particle size analysis, interfacial tension measurement, and wettability reversal experiments, while its application effect was verified by core spontaneous imbibition tests and injection enhancement evaluation experiments. The results indicate that the nano-emulsion has a median particle size of approximately 12 nm, which can reduce the oil-water interfacial tension to 0.00165 mN/m, significantly decreasing the flow resistance of crude oil. It can reverse the contact angle of oil-wet quartz plates from 130.9° to 11.9°, realizing the transformation of rock wettability to strong water wettability while reducing surfactant adsorption loss. Core experiments show that the spontaneous imbibition oil recovery is improved by 28.1%, the nano-emulsion system reduces the injection pressure of tight cores by approximately 20%, and the dynamic seepage oil recovery of cores is enhanced by 22.6%, demonstrating both excellent injection enhancement performance and oil displacement efficiency. Field applications confirm that the nano-emulsion system is adaptable to the harsh conditions of tight oil reservoirs, providing a new technical approach and practical support for the efficient development of tight oil reservoirs.

  • 1
• High-efficiency modification of heavy oil through aquathermolysis regulated by free radical initiators

  ZHANG Yu, LI Jinwei, MA Yiming, MEI Shuaishuai, YAN Jinlun, 张龙力

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

  Abstract:

  The high viscosity of heavy oil presents a major challenge to its efficient extraction. Aquathermolysis has emerged as a promising technique for in-situ upgrading, offering advantages such as effective viscosity reduction and high recovery rates. However, its practical application is limited by the high activation energy required for the chain initiation step, which necessitates elevated reaction temperatures and results in substantial energy consumption. To address this limitation, this study investigates the use of radical initiators to lower the energy of the initiation stage. Four initiators—di?tert?butyl peroxide (DTBP), azobisisobutyronitrile (AIBN), potassium persulfate (K?S?O?), and iodine (I?)—were systematically evaluated for their enhancing effects on the aquathermolysis of Shengli heavy oil under mild conditions. The results demonstrate that all initiators improve the viscosity?reduction performance, following the order of effectiveness: DTBP > AIBN > K?S?O? > I?. DTBP exhibited the most pronounced effect, achieving a viscosity reduction rate of 75.59 %, which represents a 27.48 % increase over the control experiment. Additionally, the contents of heavy components (asphaltenes and resins) further decreased, and the flow activation energy was significantly reduced. These macroscopic findings confirm that initiators enhance oil fluidity and quality by intensifying the cracking reactions. At the molecular level, 13C NMR analysis revealed that the initiators promote hydrogenation, ring?opening, and chain?scission reactions. Electron paramagnetic resonance (EPR) spectroscopy further provided direct evidence from the radical perspective, showing that the initiators raise the stable free?radical concentration from 4.38 to 6.42 μmol/g?oil, thereby boosting the cracking activity. This multiscale investigation elucidates the effect and mechanism by which radical initiators strengthen aquathermolysis, offering valuable insights for the development of energy?efficient and effective heavy?oil upgrading processes.

  • 1
• Technical Review of Chelation-Based Descaling Theory in Oil and Gas Extraction

  YANG Xiaojiang, SU Hetian, ZHANG Baoyue, FY Bo, HU Yongqiang, JIANG Yinyifan, WU Yucong, MAO Jincheng

  Abstract: (83) HTML (0) PDF (0.00 ByteKB) (0)

  Abstract:

  This paper focuses on scaling issues in oil and gas extraction processes and their chemical control strategies. It provides a systematic review of the mechanisms of action and performance characteristics of different types of chelating agents, with a particular emphasis on the synergistic mechanisms of blended composite descaling agents. The paper provides a detailed introduction to the structural characteristics, mechanisms of action and application limitations of common chelating agents, including inorganic phosphates, organic phosphonates, aminocarboxylic acids, hydroxycarboxylic acids, polymers, green chelating agents and macrocyclic polyethers, and illustrates the differences in their descaling efficacy through practical examples. The paper further analyses the key roles of formulation additives—such as solubisers, surfactants, dispersants and conversion agents—in enhancing the efficiency of chelation-based descaling; it summarises multiple synergistic mechanisms including pH regulation, dispersion stabilisation and precipitation conversion. It outlines future development directions for descaling technology, emphasising the need to focus on developing new, environmentally friendly and highly targeted chelating agents. Through multi-component formulation and process optimisation, the aim is to achieve a balance between descaling performance and ecological safety. The applicability of these approaches can be extended to various industrial sectors, including chemical processing, food processing, water treatment and seawater hydrogen production, thereby providing theoretical support and technical guidance for the management of scaling in industrial systems.

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• Quality Surveillance of Drilling Fluid Materials: Current Status, Challenges and Strategies

  LIU Changyue, CHEN Ziyu

  Abstract: (85) HTML (0) PDF (0.00 ByteKB) (0)

  Abstract:

  The exploration and development of global oil and gas resources are expanding into complex areas such as deep, ultra-deep, and unconventional formations. Drilling engineering has increasingly high quality requirements for drilling fluid materials. However, the currently uneven quality of drilling fluid materials poses significant risks to drilling operations, wellbore quality, and environmental protection. This study aims to identify the predicaments faced by China's oil and gas exploration enterprises in drilling fluid material quality management, pinpoint the critical factors affecting quality performance, and propose effective countermeasures to enhance the efficiency of oil and gas exploration in China. A systematic analysis of the quality control mode and application effects of drilling fluid materials by large oil exploration and development enterprises such as CNPC, combined with statistical results of enterprises and products certificated by CNPC in the past 10 years, reveals prominent issues in the quality supervision of drilling fluid materials in China's oil exploration and development process. These issues include an imperfect standard system and inadequate implementation, complex additive components with insufficient effective components, uneven product quality in the market, limitations in quality inspection and evaluation methods, insufficient attention to environmental protection and waste disposal, etc. It is found that the current surveillance mode targeting the functional performance of drilling fluid materials is the fundamental cause of the current quality issues of drilling fluid materials. It is proposed to improve the standard system and establish a quality control mode centered on chemical composition analysis throughout the entire quality surveillance lifecycle, providing technical support for China's oil and gas enterprises in carrying out quality control of drilling fluid materials.

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• Preparation and Application of Selective WSO/Sand Stabilization Integrated Particles for High Water-Cut and Sand-Producing Reservoirs

  ZHU Liguo, CHEN Weiyu, ZHANG Yanhui, WEI Ziyang, WANG Jinlin, JI Wen

  Abstract: (123) HTML (0) PDF (0.00 ByteKB) (0)

  Abstract:

  Aiming at the dual technical challenges of WSO and sand control in high water-cut and sand-producing reservoirs, a kind of selective WSO/sand stabilization integrated particle was developed by using oil-soluble resin particles, sodium-based bentonite, lignosulfonate dispersant, and cationic polyacrylamide as main raw materials.Performance tests including sand stabilization and selective WSO show that:The median particle size of this particles is 8.51 μm and the water-phase dissolution rate is 9.83% with a core plugging rate of 84.5%, while the oil-phase dissolution rate is 82.61% with a core plugging rate of 15.8%. It can bond sand grains in the core into clusters, increasing the median sand grain size by more than 8.8 times and the critical sand-producing velocity by more than 20 times.indicating an obvious selective plugging and sand stabilization effect.

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• Evaluation and Mechanism of Crude Oil Composition on Enhanced Oil Recovery by Low-Salinity Water Flooding

  LI Ye, TAO Jin, REN Jingbao

  Abstract: (106) HTML (0) PDF (0.00 ByteKB) (0)

  Abstract:

  The oil displacement efficiency of low-mineralization brine is mainly influenced by the interaction among crude oil, brine and rock. Clarifying the relationship among the three is crucial to understanding the dominant mechanism of enhanced oil recovery (EOR) by low-mineralization brine. High-temperature and high-pressure core flooding experiments were conducted on various crude oil samples with different emulsion formation capabilities, including spontaneous imbibition of high-mineralization brine and displacement by low-mineralization brine. The injection process of low-mineralization brine in the tertiary oil recovery mode was simulated to investigate the impact of crude oil microemulsion formation capability and rock wettability changes on the recovery rate of low-mineralization brine flooding. The results show that the cumulative recovery rates of high-mineralization brine spontaneous imbibition and water flooding for the eight oil samples range from 37.6% to 55.9%. When low-mineralization brine is continuously injected in the tertiary oil recovery mode, the recovery rate can be further increased by 0.5% to 10.8%. The stronger the microemulsion formation capability of the oil sample, the higher the recovery rate of low-mineralization brine flooding, but the upper limit of the recovery rate increase by low-mineralization brine flooding is 11%. When the crude oil particle dispersion ratio is greater than 7, the recovery rate of low-mineralization brine flooding for this oil sample can reach more than 5%. Low-salinity brine enhances oil recovery through two mechanisms. On one hand, it forms emulsions with crude oil, promoting the stripping of oil from rock surfaces and the rearrangement of active components, enhancing water-rock reactions and shifting wettability to water-wet. On the other hand, emulsification induces the Jamin effect to increase seepage resistance, raising injection pressure and displacement differential pressure under constant-rate injection, and expanding sweep efficiency. The findings provide a reference for the application of low-salinity brine flooding and the precise screening of suitable reservoirs.

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• Factors Influencing the Oil Displacement Efficiency of Alkali-Free Binary System Assisted by Nano-SiO2 in Low-Permeability Reservoirs

  WU Jingchun, FU Zulong, SHI Fang, Li Ziqiang, Zhang Chunlong

  Abstract: (253) HTML (0) PDF (0.00 ByteKB) (0)

  Abstract:

  An alkali-free composite system, denoted as CHS-x (where x represents the nano-SiO? concentration), was constructed comprising anionic heavy alkyl benzene sulfonate (HABS), zwitterionic cocamidopropyl hydroxysulfobetaine (CAPH), and nano-SiO?, tailored for the low-permeability reservoir characteristics of a specific block in the Changqing Oilfield. The CHS-x systems were characterized via FTIR, particle size analysis, and SEM, followed by evaluations of interfacial tension (IFT), wettability alteration, emulsification performance, and adsorption behavior on reservoir rocks. Experimental results demonstrated that the CHS-0.15% formulation maintained an IFT in the order of 10?3 mN/m after 60 days of static aging at 45°C and a formation water salinity of 11,000 mg/L, exhibited a water separation rate of only 26% after 30 days, and effectively altered oil-wet core slices to weakly water-wet conditions (reducing the contact angle from 105.2° to 61.2°), with nano-SiO? significantly enhancing resistance to adsorption losses. Core flooding simulations indicated that injecting 0.7 PV of the CHS-0.15% system (composed of 0.15 wt% nano-SiO? and 0.3 wt% surfactants with an HABS:CAPH mass ratio of 7:3) increased oil recovery by 28.63% compared to water flooding, showing enhanced recovery across permeability contrasts of 2 and 5; these findings provide targeted technical insights for addressing development challenges in low-temperature, low-permeability reservoirs analogous to those in the Changqing Oilfield.

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• Research Progress on Reservoir Damage Mechanisms and Prevention Strategies During CO2 Enhanced Oil Recovery and Storage

  CHEN Jun, ZHANG Dingxue

  Abstract: (177) HTML (0) PDF (0.00 ByteKB) (0)

  Abstract:

  With the development of unconventional oil and gas resources, the reservoir damage caused by CO2 during oil displacement and storage, and the corresponding prevention and control strategies, are becoming increasingly prominent. Clarifying the reservoir damage mechanisms during CO2 displacement is crucial for improving the development and storage effectiveness of unconventional reservoirs. This article reviews the reservoir damage mechanisms and influencing factors, including asphaltene precipitation and wettability changes, mineral dissolution and particle migration, inorganic mineral precipitation, and salting out. It also introduces the application effects and advantages and disadvantages of different prevention and control strategies. Future trends in reservoir protection during CO2 displacement and storage are proposed. Whether it"s the development of asphaltene inhibitors and inorganic salt unblocking agents, or the optimization of injection processes, both require consideration of the complex characteristics of the reservoir in the field, posing significant economic challenges. Therefore, a prevention-oriented approach, combining process control with prevention and control, is needed to promote a shift in reservoir protection from passive management to proactive prevention, thereby enhancing the potential for CO2 displacement and storage.

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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: (1643) HTML (0) PDF (1.44 MKB)(6927)

  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: (2043) HTML (0) PDF (1.23 MKB)(4525)

  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.

• 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: (1226) HTML (0) PDF (1.18 MKB)(4502)

  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.

• 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: (2050) HTML (0) PDF (2.35 MKB)(4465)

  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: (2679) HTML (0) PDF (1.15 MKB)(4231)

  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.

• Research and field Application of High Content of Condensate Oil Resistance foam Unloading Agent

  WU Junwen1，ZHANG Rusheng1，WANG Haibo1，CEN Xueqi1，JIA Wenfeng2，Xiao Zaixin3

  2019,36(3):508-512, DOI: 10.19346/j.cnki.1000-4092.2019.03.023

  Abstract: (1353) HTML (0) PDF (1.71 MKB)(4043)

  Abstract:

  Longfengshan gas field water well is characteristic of deep well depth，high gas temperature（104—149℃）and super high content of condensate oil for some blocks. A kind of organic ammonium salt type cationic fluorocarbon surfactant was synthesized，and it was mixed with the existing foaming agent as a ratio of 1∶15，which was composed of zwitterionic surfactant cocoamidopropylbetaine and sodium alpha-olefin sulfonate at ratio of 10∶1，thus the foam unloading agent PQ-Y was developed. Its foaming ability，foam stabilizing ability and liquid carrying ability were tested and field test was also carried. Laboratory tests showed that the initial foaming height Ho and foam height after 5 min H5 of the foam unloading agent were 194 mm and 186 mm，respectively，after aging at 160℃ for 14 h，and Ho and H5 were 189 mm and 180 mm when the salinity was as high as 250000 mg/L，and Ho and H5 were 171 mm and 168 mm，respectively，when the volume fracion of petroleum ether was 50%，its liquid carrying rate was as high as 8 mL/min，which indicated that the foam unloading agent PQ-Y was resistant to the condensate oil. The field test of the foam unloading agent in Longfengshan north 201-XY well showed that，the average gas production increased from 7256 m3/day to 11329 m3/day，increasing by 56%，the average differential pressure between tubing and casing dropped from 2.66 MPa to 2.38 MPa，felling by 10.5%，both liquid yield and gas production were obvious，which proved that the foam unloading agent PQ-Y could meet the demand of drainage gas recovery for high content condensate oil gas field

• 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: (1579) HTML (0) PDF (1.32 MKB)(3982)

  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: (1774) HTML (0) PDF (1.20 MKB)(3923)

  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: (2219) HTML (0) PDF (2.17 MKB)(3804)

  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.

• 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: (1474) HTML (0) PDF (1.02 MKB)(3417)

  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: (2445) HTML (0) PDF (2.12 MKB)(3393)

  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.

• 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: (774) HTML (0) PDF (1.25 MKB)(3378)

  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 Progress of Imbibition Oil Production in Low-permeability Reservoirs

  LIU Kai1，2，GAO Zhendong3，WANG Chengjun1，2，GAO Yiwen1，2，MENG Xuangang3

  2021,38(4):747-753, DOI: 10.19346/j.cnki.1000-4092.2021.04.029

  Abstract: (885) HTML (0) PDF (1.36 MKB)(3310)

  Abstract:

  Through literature research，the relative concept of imbibition oil production was introduced，research results and the newest research progress of imbibition oil production method in low-permeability reservoirs were reviewed，and the development prospect of imbibition oil production in low-permeability reservoirs in lab experiments and field application was put forward.

• 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: (1772) HTML (0) PDF (2.10 MKB)(3103)

  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: (1451) HTML (0) PDF (1.28 MKB)(3054)

  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: (1596) HTML (0) PDF (1.38 MKB)(3007)

  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.

• 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: (1272) HTML (0) PDF (1.33 MKB)(2994)

  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.

• 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: (1775) HTML (0) PDF (1.22 MKB)(2972)

  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: (1857) HTML (0) PDF (1.78 MKB)(2938)

  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.

• Performance Evaluation of Thickener for Seawater-based Fracturing Fluid with High Temperature

  CHEN Lei，BAO Wenhui，GUO Bumin，WANG Xinzun，LI Meng，SUN Houtai

  2020,37(1):17-21, DOI: 10.19346/j.cnki.1000-4092.2020.01.004

  Abstract: (866) HTML (0) PDF (1.44 MKB)(2864)

  Abstract:

  In order to meet the demands for seawater-based fracturing fluid under the temperature of 180℃，a thickener SWF-T180 of associated polymer was synthesized with acrylamide， acrylic acid， 2-acrylamido-2-methyl-propanesulfon-icacid， N-vinylpyrrolidone， dodecanol maleic anhydride sodium and N-hexadecylacrylamide as raw material， and ammonium persulfate-sodium sulfite as initiator. The increasing viscosity，salt-tolerance，swelling，temperature-resistance of SWF-T180 and the performance of seawater-based fracturing fluid prepared by SWF-T180 were evaluated. The results showed that SWF-T180 had an obvious viscosity enhancement effect. When the dosage of SWF-T180 was greater than 0.6%，the viscosity of the fluid increased rapidly. SWF-T180 had good resistance to salt，calcium and magnesium with large dissolving capacity. The viscosity of SWF-T180 after dissolving in seawater for 8 minutes reached 84.3% of its ultimate viscosity. The temperature resistance of SWF-T180 was up to 180℃. The viscosity of seawater-based fracturing fluid composed of 1% SWF-T180 and 0.6% crosslinking agent was 60—70 mPa·s under the condition of 180℃ and 90 minutes shearing time. SWF-T180 had a good shear recovery feature，which met the requirement of offshore reservoir fracturing operation at 180℃.