Volume 42,2025 Issue 1

• ·High Temperature Resistance Fluid Loss Reducer Modified by β-Cyclodextrin

  MA Chao, LIU Yilin, TANG Jiajing, ZHOU Xu, LIU Chao

  2025,42(1):1-7, DOI: 10.19346/j.cnki.1000-4092.2025.01.001

  Abstract: (155) HTML (0) PDF (0.00 ByteKB)(0)

  Abstract:

  Oil and gas exploration and development in deep and ultra-deep well have put forward higher requirements on the temperature resistance of fluid loss reducer for drilling fluid. Taking advantage of β-cyclodextrin’s special rigid stabilizing structure in the shape of a conical ring table and special adsorption ability of inner hydrophobicity and outer hydrophilicity，β-cyclodextrin （β-CD） was grafted by maleic anhydride （MAH）. Meanwhile，3-（trimethoxymethylsilyl） propyl methacrylate （KH₅₇₀） with excellent high-temperature stability was introduced，and then copolymerized in an aqueous solution with p-styrenesulfonic acid sodium salt（SSS）and dimethyldiallylammonium chloride（DMDAAC）. As a result，a high-temperature resistance fluid loss reducer（LY-1）was synthesized. The optimum preparation conditions of LY-1 were determined by measuring the high-temperature and high-pressure filtration loss of sodium bentonite based slurry containing 3% LY-1. The structure of LY-1 was characterized by gel chromatography，infrared spectrometry and thermogravimetric analysis. The effects of LY-1 on the filtration loss and rheological properties of base slurry were evaluated. The performance of LY-1 was compared with that of three commonly used high temperature resistance fluid loss reducers. The results showed that the optimum synthesis conditions of LY-1 were obtained as follows：25% total mass fraction of the monomer，1% initiator mass fraction of the monomer mass，15∶3∶2∶15 mass ratio of the monomers（SSS，KH570，DMDAAC and MAH-β-CD），10 pH value，75 ℃ reaction temperature，and 4 h reaction time. The average relative molecular mass of LY-1 was 14 589. The total heat loss mass was about 35.98% at 284—453 ℃，which meant it had good temperature resistance at 300 ℃. LY-1 had a good performance of lowering the filtration loss at high temperatures. When 3% LY-1 was added to the base slurry，the filtration loss of base fluid was reduced from 143 mL to 12 mL after hot rolling at 200 ℃for 16 h，with a reduction rate of 91.6%. The effect of LY-1 on the rheological properties of base slurry was small. It’s filtration reduction performance and temperature resistance were better than those of three commonly used high temperature resistance fluid loss reducers.

• Development and Performance Evaluation of Anti-multivalent Cationic Filtrate Reducer

  CAO Jiajun, ZHANG Yongwei, QIN Yuqing, YU Jiashui, YU Ting, ZHU Limin, YANG Lili

  2025,42(1):8-13, DOI: 10.19346/j.cnki.1000-4092.2025.01.002

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

  Abstract:

  In oil and gas exploration and development operations，the geological conditions are complex，and the salinity of formation water in salt-gypsum layers is extremely high. A large number of metal cations have a serious negative impact on the viscosity and filtration reduction of water-based drilling fluids. In order to solve this problem，an anti-multivalent cation zwitterionic hyperbranched polymer filtrate reducer XZ-DJ2 was prepared by introducing a branching agent on the basis of zwitterionic polymer. The optimum reaction conditions were explored through experiments，and a series of characterization tests on its physical and chemical properties were carried out. The rheology，filtration loss reduction，salt resistance，particle size and Zeta potential of the drilling fluid base slurry after adding XZ-DJ2 were tested. The results showed that after adding 2% XZ-DJ2 into the base slurry，the Zeta potential changed from ?31.9 mV to ?42.4 mV，and the absolute value of Zeta potential increased，indicating that XZ-DJ2 could improve the stability of the system. The filtration loss before and after aging at the temperature of 150 ℃ for 16 h was 5.6 mL and 6 mL，respectively，which was significantly lower than that of the base slurry without XZ-DJ2，being of 26.6 mL and 31.8 mL，respectively，indicating that XZ-DJ2 had good filtration loss reduction performance. With the increase of XZ-DJ2 dosage，the viscosity of drilling fluid increased and the filtration loss decreased slightly. After contaminated by 30% NaCl、30% KCl、5% CaCl₂、5% MgCl₂ and 1% Al₂（SO₄）₃·18H₂O，the viscosity of the drilling fluid was significantly reduced，but the filtration loss change little，being of 6.3，6.2，5.2，6.8，7.0 mL，respectively，indicating that XZ-DJ2 had excellent temperature resistance and multivalent cation pollution resistance，and XZ-DJ2 achieved the fluid loss reduction effect by improving the compactness of the filter cake rather than improving the viscosity of the drilling fluid，which is conducive to drilling speed and further save drilling fluid operating costs.

• A Composite Plugging Materials for Drilling in High-temperature Deep Fractured Formations

  YANG Yuepeng, ZHANG Jianan, ZHANG Lihui, SHANG Youzhi, WANG Lei, ZHANG Hongtao

  2025,42(1):14-21, DOI: 10.19346/j.cnki.1000-4092.2025.01.003

  Abstract: (113) HTML (0) PDF (0.00 ByteKB)(0)

  Abstract:

  In order to solve effectively the leakage phenomenon during drilling in high-temperature deep fractured formations，a new type of high-temperature resistant rigid sealing agent HTD-2 was developed，and it was compounded with modified inorganic mineral fiber GXW-1 and elastic sealing material TDS-2 to form a composite sealing material. The performance of the plugging material was evaluated through temperature resistance performance experiments，crack sealing experiments，high-temperature and high-pressure sand bed sealing experiments and compatibility experiments with drilling fluid. The results showed that the temperature resistance performance of HTD-2，GXW-1，and TDS-2 was significantly better than that of walnut shell. Under high temperature and pressure conditions，a single sealing material could not achieve good sealing effects on cracks with different size， while composite sealing materials had better sealing effects. The composite sealing materials，composes of 8% HTD-2 + 1.5%GXW-1+6% TDS-2，could make the 30 min leakage of 0.5—2 mm cracks be reduced to below 100 mL，and the pressure bearing capacity of the sealing layer was greater than 10 MPa. The addition of composite plugging materials could make the drilling fluid have good sealing effect in different sizes of rock debris sand beds，with a 60 min invasion depth of only 9.3 cm for 0.85—2 mm sand beds. In addition，the composite sealing materials had good compatibility with drilling fluids. The in-site application results showed that when using drilling fluid with composite plugging materials for in-site construction，there was no significant leakage phenomenon during the drilling process of GX-1 well，and the drilling process was smooth，effectively improving drilling efficiency and quality. This composite sealing material is suitable for promotion and application in sealing construction operations in high-temperature and deep fractured formations.

• Strength Evolution and High Temperature Retrogression Mechanism of Setting Cement Temperature of 30—200 ℃

  SUN Lijun, ZHENG Guanyi, LI Chenglong, QIAN Qin, DAI Rongdong, HOU Yegui, PANG Xueyu, HAN Chao

  2025,42(1):22-29, DOI: 10.19346/j.cnki.1000-4092.2025.01.004

  Abstract: (119) HTML (0) PDF (0.00 ByteKB)(0)

  Abstract:

  To meet the requirements on well integrity of oil wells under large temperature difference environment，it is needed to clarify the evolution of mechanical properties of oil well setting cement under a wider range of temperature and pressure. Pure cement system and silica-cement system was selected as research targets，the influence of temperature，pressure and silica fume content on the evolution of cement strength under the temperature range of 30—200 ℃ was systematically studied and the driving mechanism of cement strength development and high temperature strength retrogression mechanism under each factor was investigated. The results showed that within 30—110 ℃，the compressive strength of pure cement system increased with the increase of temperature. As The temperature increased from 100 ℃ to 150 ℃，the strength retrogression of the pure cement system happened under high temperature. Within the temperature of 110—200 ℃，the ultrasonic intensity of silica-cement system changed not monotonically with the temperature；however，the ultrasonic intensity development could be accelerated by the increase of pressure. At the temperature of 200 ℃，the phenomena of strength retrogression and volume expansion of silica-cement system happened. By increasing the amount of silica sand，the early strength decline rate could alleviated to a certain extent. Phase composition analysis showed that the development of the early strength of cement was mainly related to the formation of C-S-H gel and Ca（OH）₂；at the temperature of 130 ℃，the main reason causing the high temperature strength retrogression of pure cement system was the formation of α-C₂SH；at the temperature of 200 ℃，the main reason causing the strength retrogression of silica-cement system was that the C-S-H gel was gradual transited from amorphous to other crystalline.

• Evolution Effect of Hydration Products on the Properties of Cement in High Temperature CO₂ Environment

  WEN Dayang, XIAO Wei, FENG Qinghao, CHEN Zhiming, YU Xinhu, YUAN Bin

  2025,42(1):30-37, DOI: 10.19346/j.cnki.1000-4092.2025.01.005

  Abstract: (117) HTML (0) PDF (0.00 ByteKB)(0)

  Abstract:

  Addition of quartz sand to Portland cement can prevent its mechanical properties from declining due to crystal transformation at high temperatures. However，the composition and morphology changes of hydration products of sand-coated cement under the combined action of 180 ℃ and supercritical CO₂ are more complex，so the effect of high temperature CO₂ on the mechanical properties of cement is still unclear. Therefore，the corrosion depth，pore size distribution，mechanical properties， phase composition，functional groups and microstructure of cement stone in supercritical CO₂ environment at 180 ℃ were analyzed by means of scanning electron microscopy，mercury injection，thermogravimetric analysis，X-ray diffraction test and infrared spectrum characterization. The results showed that with the increase of corrosion time，the corrosion depth of cement stone increased，the compressive strength decreased，and the porosity decreased first and then increased. The hydration products were composed of acicular xonotlite（C₆S₆H），columnar hillebrandite（C₂SH），sheet and rod-shaped calcium carbonate（CaCO₃）and loose porous amorphous SiO₂. Under the condition of supercritical CO₂ at 180 ℃，the influence mechanism of hydration product evolution of cement on its performance was obtained as follows. In the early stage of corrosion，a large amount of C₂SH and a small part of C₆S₆H were corroded to generate CaCO₃ and amorphous SiO₂. CaCO₃（mainly aragonite and vaterite）would fill part of the pores，while the polymerization degree of C-S-H gel increased，slowing down the carbonization corrosion rate. In the later stage of corrosion，the increase of calcite content could promote the development of strength to a certain extent. But with the progress of corrosion，the vaterite and aragonite dissolved，a large number of C₆S₆H were corroded and then the morphology changed toward flake and block，resulting in the increase of porosity of cement stone，the decrease of polymerization degree of C-S-H gel and compressive strength，and the acceleration of carbonization. Under supercritical CO₂ at 180 ℃，the evolution of C-S-H gel（C₆S₂H and C₆SH）and calcium carbonate（calcite，aragonite and vaterite）determined the change of mechanical properties of Portland cement.

• CO₂ Suspended Proppant Technology and Evaluation of Suspended Sand Performance for Complex Fracture Network Fracturing

  HUANG Tao, ZHONG Ying, MOU Qiuhang, YAN Yaohui, LI Jianlin, ZHANG Hao

  2025,42(1):38-43, DOI: 10.19346/j.cnki.1000-4092.2025.01.006

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  Abstract:

  Due to its low viscosity and weak sand carrying capacity，the slickwater fracturing fluid is often unable to meet the efficient filling of proppant in complex fracture networks post-fracture. Based on the theory of bubble suspended sand，a CO₂ suspension proppant technology was proposed and the CO₂ suspension sand effect in slickwater fracturing fluid was evaluated under normal temperature and pressure，high temperature and high pressure，respectively. The results showed that the surface modified coating of suspended proppant could play a stable gas-solid bridging effect. For the surface modified suspended proppant，the adsorption of CO₂ and the bridging effect of proppant could effectively reduce the specific gravity of proppant，significantly slow down the settling speed of the proppant in slickwater with a reduction of 99%，being of 0.15 cm/min，thus achieving the effect of “low formation damage and high sand carrying capacity”. The performance of CO₂ suspended sand under the condition of normal temperature and pressure was mainly affected by the viscosity of slickwater. The degree of suspension and stable suspension duration increased with the increase of viscosity of slippery water fracturing fluid，but it is basically not affected by sand concentration. Under the condition of high temperature and pressure，carbon dioxide was in a supercritical state（SC-CO₂），but it could still adsorb on the surface of suspended quartz sand and play a certain suspension role，causing a large amount of suspended quartz sand to be suspended during the stirring process. CO₂ suspension proppant technology can significantly improve the sand carrying capacity of slickwater，and has important practical significance to reduce the risk of sand plugging in complex fracture networks and improve the efficiency of oil and gas well reconstruction by efficient proppant filling.

• Microemulsion Stimulation Agent for Fracturing of Low Permeability Tight Oil Reservoir

  LIU Qian, WEN Xiaoyong, WANG Wenxiong, LIU Yi, YIN Taiheng, MA Huan, DING Yong, JIA Jianpeng

  2025,42(1):44-51, DOI: 10.19346/j.cnki.1000-4092.2025.01.007

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  Abstract:

  In order to achieve imbibition stimulation of low permeability tight oil reservoirs，a microemulsion additive（ME）for increasing production by imbibition stimulation was developed， based on the integrated construction method of “compression-injection-recapture”and with the goal of improving the performance of fracturing fluids. The major raw ingredients were fatty alcohol alkoxylation sulfate anionic surfactant（SY-1）and methyl 9-octanoate（MS-9）. The phase behavior was explored by fitting a ternary phase diagram，and then the formula was optimized using orthogonal tests. Its performance was evaluated by laboratory experiment，and then the stimulation effect during fracturing was tested. The results showed that the optimum formula for preparing ME was obtained as follows：25% SY-1，12.5% triethylene glycol butyl ether，37.5% KCl aqueous solution（2%mass fraction） and 25% MS-9. The average particle size of the microemulsion was 70.5 nm. It could keep stable under the conditions of long standing（180 days）and high-speed centrifugation（8000 r/min）. It could also reduce the interfacial tension to the order of 10^-4～10^-3 mN/m. Compared with water，it could reduce the contact angle by approximately 35°. It could maintain high interfacial activity after 8 adsorptions with core powders，indicating strong anti-sorption ability. It had good compatibility with fracturing fluid. When the fracturing fluid without ME was used as blank control，ME could enhance the oil washing efficiency by 54.94 percentage points—61.82 percentage points during the simulated fracturing entry stage. During the simulated fracturing well stage，the imbibition displacement impact might be raised by 15.68 percentage points. Meanwhile，during the flowback stage，it could accelerate the speed and degree of crude oil recovery，and then the crude oil recovery rate could be increased by 32.56 percentage points. The microemulsion had the advantages of small particle size，strong stability，low interfacial tension between oil and water，good wetting improvement effect and strong adsorption resistance. It could increase oil recovery during the whole process of fracturing construction. The effect of increasing permeability and oil displacement was remarkable.

• A Self-healing，Quick-dissolving and Hydrochloric Acid-resistant Thickener Based on Strong Amphiphobic Interaction

  FANG Yuyan, SHI Wenjing, FANG Junwei, PAN Lijuan, JIAO Kebo, LI Liang, WANG Yanling, LIANG Shinan

  2025,42(1):52-58, DOI: 10.19346/j.cnki.1000-4092.2025.01.008

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  Abstract:

  Acidizing and acid fracturing reservoir reconstruction technology is an important means to increase production. Traditional dry powder acid thickener has a dissolution time of more than 2 h when used to prepare acid solution，which makes it impossible to continuously mix on site. As for the emulsion thickener with better solubility，acid resistance，salt resistance and shear resistance in special environment need to be improved. In this paper，using APS/TEMPO composite catalyst，acrylamide （AM），fluorine-containing，sulfonate-containing and ammonium chloride-containing monomers as raw materials，a self-healing， quick-dissolving and hydrochloric acid-resistant thickener PASD based on strong amphiphobic interaction was prepared by inverse emulsion polymerization. The chemical structure of PASD was characterized by infrared spectroscopy，and its relative molecular mass，stability，acid resistance，acid dissolution time，temperature resistance，salt resistance，shear resistance，amphiphobic inversion and displacement performance were tested. The thickener PASD had excellent chemical stability. When the concentration of inorganic salt ions was less than 50 mg/L，the viscosity could be maintained above 24 mPa·s. PASD could be dissolved in 20 % hydrochloric acid within 3 min，and the viscosity of tackifying acid could reach up to 38 mPa·s. When destroyed by strong shear，the viscosity self-healing rate of the tackifying acid was 65% within 30 min. The gel breaking liquid of PASD tackifying acid could result in wettability reversal of rock with strong-amphiphobic（super-hydrophobic and strong oleophobic），reduce capillary action and driving pressure，and communicate with the pore cracks of the formation to a greater extent. This study provides a material basis for the realization of on-line mixing of acid liquid and the integration of thickened acid fracturing and replacement.

• Development and Field Application of Chelating Acid System for Formation Damage Remove In 160 ℃ High-temperature Offshore Sandstone Gas Reservoirs

  CHENG Yuxiong, PENG Chengyong, WU Guang’ai, SHI Weiqi, CHEN Minggui, JIANG Hu, WU Bailie

  2025,42(1):59-67, DOI: 10.19346/j.cnki.1000-4092.2025.01.009

  Abstract: (89) HTML (0) PDF (0.00 ByteKB)(0)

  Abstract:

  During the acidification of 160 ℃ high temperature sandstone reservoirs in offshore WC oilfield，the clay minerals such as illite are hydrated and decomposed in hydrochloric acid，causing particle migration and reservoir damage，resulting in reduced productivity of oil and gas wells. To solve the problems of fast reaction at high temperatures，sensitivity of illite clay，and short penetration distance of conventional mud acid，experiments such as high-temperature acid dissolution，core flooding，and produced liquid ions analysis were carried out，and a high-temperature resistant chelating acid，composed of 5% GLDA+8% acetic acid+1%HF+1.5% clay stabilizer NW-1+1% corrosion inhibitor CT-1，was proposed. The chelating acid achieved a dissolution rate of 15.2% at the temperature of 160 ℃ for 16 hours，a corrosion rate of 3.7451 g/（m²·h），and an anti-swelling rate of 90.9% . After the chelating acid interacted with the rock core，Si⁴⁺，Ca²⁺，Mg²⁺，and Fe³⁺ content gradually increased，indicating that the chelating acid had a multivalent metal ion chelating effect，which could avoid secondary and tertiary damage to the rock core by the acid solution，achieving the effect of the acid dissolution on deep penetration of the formation. In response to the lack of mature professional software for chelating acid acidification design，a simplified acid rock reaction plane radial flow model was used， considering the material balance of hydrofluoric acid，a chelating acid acidification simulation design software was developed using MATLAB language. The optimal acid injection rate for Well A was calculated to be 2 m³/min，and the volume of acid used in each section did not exceed 70 m³. The chelating acid system was successfully used to remove blockages in 5 offshore water injection wells. After the measures，the average daily injection volume increased by more than 110 m³，and the injection pressure decreased significantly，with a maximum pressure drop of 12 MPa. The chelating acid system had a good effect on removing blockages and increasing injection in the 160 ℃high illite sandstone gas reservoir.

• Preparation and Performance Evaluation of Gel Profile Control System with Temperature and Salt Resistance

  DU Jie, YUAN Fenggang, CHEN Ruibing, XIE HUI, ZHANG Hanqing, YUAN Enlai

  2025,42(1):68-74, DOI: 10.19346/j.cnki.1000-4092.2025.01.010

  Abstract: (101) HTML (0) PDF (0.00 ByteKB)(0)

  Abstract:

  In order to solve the problems of inefficient，ineffective circulation of injected water and imbalanced injection and production in the later stage of oilfield development due to intensified contradictions in reservoir profile and development of dominant channel of water flow，a temperature and salt resistant gel profile control system was developed using hydrophobic associating ploymer as the main agent，organic aluminum zirconium crosslinking agent made from inorganic salt aluminum and zirconium oxychloride as the main crosslinking agent，and sodium lignosulfonate heat stabilizer as the auxiliary. Its gelling performance，anti-dilution performance，shear resistance，plugging performance and erosion resistance were studied. The optimal formula for the profile control system was as follows：0.4% hydrophobic associating polymer，0.3%—0.35% organic aluminum zirconium crosslinking agent and 0.2% heat stabilizer. The research results indicated that the viscosity of the base liquid was 88.3—95.8 mPa·s，and the low viscosity base fluid endowed with better pumping performance，which could ensure the construction safety. Under the condition of 200 ℃ and salinity of 27 123.5 mg/L，the gelation viscosity of the system within 90 d could be maintained above 6000 mPa·s，and the viscosity retention rate could reach above 80%. When diluted with 60% of the formation water，the gelation viscosity of the system could still reach over 4000 mPa·s，and the dilution after gelation had a smaller impact on the gelation strength of the system. The system has good migration ability in cores with permeability of 500×10^-3，1000×10^-3 and 2000×10^-3 μm²，respectively，and the pressure gradually stabilized at a distance greater than 50 cm from the injection end of the rock core，and plugging rate was over 80%. With the displacement of a large amount of injected water，the permeability of the injected profile control system remained basically unchanged，exhibiting good erosion resistance.

• Preparation and Performance Control of Temperature and Salinity Resistant Polymer Gel

  XUE Xinfang, XU Guorui, FAN Haiming, LI Lingyu, YANG Hang, WANG Yefei

  2025,42(1):75-81, DOI: 10.19346/j.cnki.1000-4092.2025.01.011

  Abstract: (102) HTML (0) PDF (0.00 ByteKB)(0)

  Abstract:

  The dominant seepage channel in the middle and later stages of oilfield development leads to the increase of water cut and the decrease of oil production in oil wells. In order to improve the stability of gel profile control agent in high temperature and high salt harsh reservoirs，based on the phenomenon that the basic crosslinking system composed of low concentration polymer and phenolic crosslinking agent is easy to degrade and dehydrate under the condition of high temperature and high salt，the gel strength and dehydration rate were taken as the main indexes，and the additives that could improve the stability was optimized through semi-quantitative analysis method. The gel strength，temperature resistance and salt tolerance of the obtained gel system were evaluated. The experimental results showed that the addition of antioxidant 1#（compounds containing nitrogen）and complexing agent 2#（organic phosphonate）to the polymer gel system could significantly enhance the stability of the system. Under the condition of salinity of 45 550 mg/L（calcium ion content of 3120 mg/L），the gel system，composed of 0.4% polymer + 0.4%crosslinking agent +1.8% complexing agent 2# + 0.5% antioxidant 1#，had a gel strength of H grade at the temperature of 125 ℃， which was stronger than that of the basic crosslinking system. The gel strength could still reach grade E at the temperature of 140 ℃and the gel dehydration rate was only 5.2% after aging for 180 days，exhibiting excellent temperature and salt resistance. The gel system had good injectivity and plugging performance，the plugging rate being greater than 98%，which was suitable for reservoirs with the temperature of 90—140 ℃，and provided technical support for oil stability and water control in complex and harsh reservoirs.

• Double Cross-linked Gel Plugging Agent Used in High-temperature and High-Salinity reservoirs

  YANG Zuguo, GUO Jixiang, MA Qingjie, GUO Jintang, GAO Qiuying

  2025,42(1):82-89, DOI: 10.19346/j.cnki.1000-4092.2025.01.012

  Abstract: (101) HTML (0) PDF (0.00 ByteKB)(0)

  Abstract:

  The existing gel has the problems of short gel time，poor dilution resistance and poor long-term stability under high temperature formation conditions. Based on a two-level cross-linked structure design，a temperature and salt-resistant double cross-linked gel profile control and plugging agent was synthesized using glycidyl methacrylate（GMA）and diethylene glycol dimethacrylate（EDMA）as copolymer monomers，tert-butyl hydroperoxide（TBHP）as the initiation system，polyethylene glycol （PEG）as organic solvent，and fumed silica（AEROSIL）as the reinforcing agent. The effects of each component dosage on the gelling time and storage modulus of the gel were studied. The performance of viscoelasticity，aging stability，dilution resistance to formation water and plugging property of the gel were investigated. The results showed that the optimal formula of gel system was 10% GMA+ 0.7% EDMA+ 0.066% TBHP+3% AEROSIL，and the rest was PEG solvent. The initial viscosity of the system was 315 mPa·s，the gelling time was 2—10 hours，the storage modulus was 5230 Pa，and the compressive strength was 0.221 MPa. After aging for 30 days at the temperature of 140 ℃ in the simulated formation water with a salinity of 2.2×10⁵ mg/L，there was no volume shrinkage，and the storage modulus could reach more than 4000 Pa. The gel had good dilution resistance to formation water. When adding formation water with volume fraction of 40%，the shear strength of the gel was reduced by about 18%，but the storage modulus could still reach more than 4000 Pa. The gel base fluid showed good injection stability，and the reverse breakthrough pressure gradient in the displacement experiment reached 5.5 MPa/m，the mechanical strength of the formed gel could meet the needs of plugging fracture channels. A potential plugging and regulating material for high-temperature and high-salinity reservoirs was provided.

• Rubber Powder Doped Thermoplastic Flexible Particle Plugging Agent

  YANG Zuguo, XI Linghui, GUO Jixiang, XUE Yan, LI Liang, LI Shenglin

  2025,42(1):90-97, DOI: 10.19346/j.cnki.1000-4092.2025.01.013

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  Abstract:

  Long-term water injection in oilfields leads to high water cut in oil wells，necessitating the development of environmentally friendly，low-cost，high-quality，and efficient chemical agents for profile adjustment and water shutoff. Using polyvinyl alcohol （PVA），rubber powder，glutaraldehyde，and a self-prepared hydrophobic modifier as raw materials，a thermoplastic flexible particle profile adjustment and water shutoff agent that could be formed in one step in aqueous phase was prepared. The particle size and microstructure of the profile modification and water shut-off agent were analyzed，and then its mechanical properties were evaluated using texture analysis method. The stability of the agent was examined under the conditions of high-salinity water and temperatures ranging from 120 ℃ to 200 ℃. A full-penetration fracture model was used to investigate the injection，transport and blockage effects of the agent in fractures. The results showed that when the mass ratio of rubber powder and PVA was between 0 and 1.75，flexible particles with an advantageous particle size of 10—20 mesh（2.00—0.85 mm）could be prepared，significantly reducing synthesis costs. Compared to particles without rubber powder，the rubber powder-doped flexible particles exhibited a loose and porous structure，higher thermal stability，and better mechanical properties. The weight loss temperature increased from 200 ℃ to 300 ℃，the hardness increased from 18.73 N to 37.31 N，the elasticity increased from 0.86 to 0.99，the resilience increased from 0.48 to 0.60，and then the chewiness increased from 15.39 N to 35.88 N. The flexible particles remained stable in high-temperature and high-salinity water，without impact on mechanical properties after aging 60 days at 120 ℃. The particles exhibited good thermoplasticity，beginning to adhere together after aging 3 days. Physical model experiments demonstrated that rubber powder-doped flexible particles could form stable pressure fluctuations，quickly adapt to fracture deformation and pressure changes，and effectively block fractures，with a blockage efficiency of 85.7%. The rubber powder-doped flexible particles possessed excellent deformability，thermal stability and injectivity，which were suitable for improving deep liquid flow redirection in high water cut oilfields and enhancing oil recovery.

• Water Control and Oil Increasing Effect of Organic-inorganic Nano-hybrid Gel in Deep Fractured Reservoirs

  QIAN Zhen, LI Jinghui, LYU Dongfang, ZHANG Wen, ZHEN Enlong, QU Bochao, LI Zongrui, ZHAO Guang

  2025,42(1):98-107, DOI: 10.19346/j.cnki.1000-4092.2025.01.014

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  Abstract:

  As the development of deep fractured reservoirs，water channeling has become increasingly prominent，leading to the wastage of formation energy and a decrease in oil recovery efficiency. The primary cause of water channeling in these complex fracture networks is extreme heterogeneity. Urgent measures are required to plug these water breakthrough channels，with plugging agents playing a central role in addressing this challenge. Deep fractured reservoirs are characterized by high temperatures（≥ 110 ℃）and high salinity（≥20×10⁴ mg/L）. Under these conditions，conventional gels struggle to maintain stability. To overcome these challenges，modified nano-silica was synthesized by introducing hydroxyl and phenolic hydroxyl groups into nano-silica through diazotization and oxidation reactions using 3-amino-4-hydroxybenzenesulfonic acid. This modified nano-silica was then reacted with nonionic polymer，hexamethylenetetramine（HMTA），and hydroquinone to produce a nano-hybrid gel. The formula of nano-hybrid gel was optimized based on gelation performance and dehydration rate. The stability，viscoelasticity and blocking capability of nano-hybrid gel were evaluated. A temperature and pressure-resistant visualized fracture network model was established according to the geological model of typical deep fractured reservoirs in Northwest oilfield. The residual oil distribution patterns were analyzed，and then the multi-round blocking effectiveness was determined. The results showed that the nano-hybrid gel with formula of 0.8% nonionic polymer，0.2% modified nano-silica，0.4% HMTA and 0.4% hydroquinone could remain stable for up to 60 days at temperatures ≤140 ℃ with a dehydration rate <10% . Modified nano-silica significantly enhanced the viscoelastic properties of nano-hybrid gel. The nano-hybrid gel exhibited excellent blocking effects on single fractures with various scales （1—10 mm）. Under the condition of 140 ℃，2 MPa backpressure and 22 × 10⁴ mg/L salinity，multi-round blocking experiments with nano-hybrid gel increased the recovery efficiency of fracture network model by 15.9 percentage points. The nano-hybrid gel demonstrated superior thermal and salt resistance，viscoelasticity and long-term stability，which made it well-suited for effective plugging and enhanced oil recovery in deep fractured reservoirs.

• Growth Law of Indigenous Microorganisms Producing Dispersions in Low Permeability Reservoirs and Its Potential for Profile Control and Plugging

  GAO Yiwen, WEI Dengfeng, WANG Weibo, NI Jun, GUAN Yaqian, GUO Maolei, WANG Qianrong, CUI Kai

  2025,42(1):108-117, DOI: 10.19346/j.cnki.1000-4092.2025.01.015

  Abstract: (80) HTML (0) PDF (0.00 ByteKB)(0)

  Abstract:

  The tight-low permeability reservoirs in Yanchang oilfield of Ordos Basin are characterized by low matrix permeability，strong heterogeneity and widespread presence of naturally developed micro-scale fractures. These lead to the problem of fluid easily flowing along fracture channels and high-permeability pore throats during water flooding and CO₂ flooding. Traditional profile control and water shutoff technologies are only effective in the near-wellbore area，which can improve the water absorption profile of injection wells but fail to fundamentally solve the water channeling problem in the deep formation. To address these issues，a green and low-carbon microbial dispersion profile control and plugging agent was developed based on endogenous microorganisms and their metabolic products as growth nuclei，which were dispersed as small spheres in the water phase （i.e.，microbial dispersions）. The results showed that the optimum activation and growth conditions for the microbial dispersion-producing functional strain（Novosphingobium sp.，similarity 98%—99%）were obtained as follows：45 ℃ temperature，60 g/L salinity，7 pH value. The most suitable activation nutrient formula was obtained as follows：carbon source（1.5% molasses），mixed nitrogen source（0.50% sodium nitrate，0.30% ammonium sulfate），trace elements（0.06% industrial yeast powder，0.002% ferrous sulfate， 0.002% manganese sulfate）. Meanwhile，the mechanism of microbial dispersion profile control and plugging was preliminarily clarified. The microbial dispersion-producing functional bacteria formed a matching plugging with the reservoir fracture channels by utilizing their individual adaptive growth and deformation properties，and then continuously migrated and controlled the profile in the deep part of fractures and high-permeability porous media，thereby changing the flow direction of injected water/CO₂ gas and ultimately achieving full profile control. The microbial dispersion had good profile control and plugging capabilities in water flooding/CO₂ flooding environments，with plugging rates all above 80% . The research results provided a reference for the application of microbial dispersion profile control and plugging technology in controlling the fracture channeling zones and high-permeability porous media channeling zones in low-permeability tight oil reservoirs and enhancing oil recovery.

• Research and Application of Fine Layered Chemical Sand Control in Complicated Fault-block Reservoir

  LI Jianda, QIAN Qin, CAO Gongze, LI Peng, WANG Guoqiang, HAN Hong

  2025,42(1):118-123, DOI: 10.19346/j.cnki.1000-4092.2025.01.016

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

  Abstract:

  To solve the problem of the uneven injection of sand consolidating agents in strong heterogeneous reservoir，a water-soluble low-viscosity surfactant sand consolidation system was prepared，and the injection performance and the influencing factors of the sand consolidation performance of the system were investigated. A fine layered chemical sand control technology was carried out based on the intralayer low viscosity active agent sand consolidation and interlayer selective separate-layer sand control. Indoor tests showed that the low viscosity active sand consolidation system was characterized by the good injectability，low damage and high consolidation strength. The viscosity of the sand consolidation system with 10% modified epoxy resin and 1%ethylenediamine content was 4.5 mPa s，exhibiting good flowability. The sand consolidation system was suitable for the reservoir temperature of 50—90 ℃. The permeability of the cemented core formed by the sand consolidation system and quartz sand was higher than 1 μm²，and the compressive strength was higher than 5 MPa，and it had good dynamic erosion resistance. The selective seperate-layer chemical sand control string was complemented based on the injection parameter optimization，which could implement the selective injection of sand consolidation agents. The fine layered chemical sand control performed well in field tests. After a cumulative production of 2700 days，the liquid production of the test well was 52.4 m³/d，and the oil production was 5.3 t/d. The effective period had been significantly improved. It is of great significance to prolong the lifespan and increase the efficiency of sand control wells in complex fault-block reservoir.

• Mechanism of Oxygen-enriched Combustion of Heavy Oil and Kinetic Parameters under Different Oxygen Contents

  GUO Wen, WU Qingxin, TANG Junshi, GUAN Wenlong, YUAN Shibao

  2025,42(1):124-131, DOI: 10.19346/j.cnki.1000-4092.2025.01.017

  Abstract: (117) HTML (0) PDF (0.00 ByteKB)(0)

  Abstract:

  Heavy oil oxygen-enriched fire flooding is an enhanced in-situ combustion technology，which can effectively improve the combustion efficiency of heavy oil by injecting high concentration oxygen. However，there are few studies on the mechanism of heavy oil oxygen-enriched combustion and the kinetic parameters under different oxygen contents. In order to clarify the effect of oxygen enrichment on the oxidation characteristics of heavy oil in-situ combustion，Liaohe heavy oil was taken as an example. The simultaneous thermal analyzer was used to study the thermal weight loss and exothermic characteristics of heavy oil oxidation under different oxygen concentrations and heating rates. Based on the iso-conversional method，the activation energy under different conversion rates and different oxygen concentrations was calculated，and then the improvement effect of oxygen enrichment on in-situ combustion was studied by numerical simulation. The results showed that the oxidation of heavy oil under oxygen-rich environment could still be divided into four stages：pre-low temperature oxidation，low temperature oxidation，coke deposition and high temperature oxidation. With the increase of oxygen dosage from 20% to 100%，the oxidation reaction was more intense，the reaction rate was larger，the heat release increased，and then the corresponding coke deposition stage was advanced by 20 ℃. The change trend of activation energy under different oxygen concentrations was the same. In the low temperature oxidation stage，the oxygen concentration had little effect on the activation energy. While in the high temperature oxidation stage，the response was intense，and then the activation energy was reduced by 15—25 kJ/mol. At the same oxygen concentration，the increase of heating rate would lead to thermal hysteresis. The numerical simulation study verified that the oxygen-enriched condition could effectively improve the combustion effect of fire flooding. When the oxygen dosage increased from 30% to 50%，the cumulative oil production increased by 11 234 m³. When the oxygen dosage increased from 70% to 100%，the cumulative oil production increased by 3753 m³. It was recommended to use 50%—70% oxygen as the injection gas of oxygen-enriched fire flooding. With the increase of oxygen concentration，the leading edge temperature（350—450 ℃）increased，which improved the stability of combustion and the combustion effect of conventional fire flooding.

• Recovery of Heavy Oil Remaining after CO₂-EOR by Micellar Solubilization

  YANG Li’an, LI Jianshan, LYU Wei, QU Xiao, LI Moyi, FANG Yiwei, ZHAO Xuezhi, FENG Yujun

  2025,42(1):132-139, DOI: 10.19346/j.cnki.1000-4092.2025.01.018

  Abstract: (93) HTML (0) PDF (0.00 ByteKB)(0)

  Abstract:

  During CO₂-EOR，supercritical CO₂ will extract the light components in the crude oil，resulting in the heavy components residue，which not only makes it difficult to greatly enhance the oil recovery，but also causes blockage of the pore throat and irreversible damage to the reservoir. To solve this problem，a new idea of surfactant micelle solubilizing heavy components after CO₂ flooding was proposed in this work. Sodium dodecylbenzene sulfonate and aliphatic alcohol polyoxypropylene ether sulfate were selected to investigate their micellar solubilization behavior for heavy components. The changes of micelle size and morphology during solubilization were investigated by dynamic light scattering and transmission electron microscopy. The results showed that the surfactant micelles could solubilize effectively the heavy components after CO₂ flooding. The maximum solubilization capacity of 0.2% surfactant solution to heavy alkanes and heavy aromatics was 2.5 g/L and 3.2 g/L，respectively. Heavy alkanes were more soluble in micelle core while heavy aromatics in palisade layer.

• Preparation and Properties of High Carbon Wax Crude Oil Emulsion Wax Inhibitor

  REN Yongcang, HUANG Yu, XU Haixia, DAN BO, YAN Dongyin, YU Haiyang, MA Jinlong, ZHANG Yupeng, HAN Guoqiang, ZHENG Cunchuan

  2025,42(1):140-147, DOI: 10.19346/j.cnki.1000-4092.2025.01.019

  Abstract: (80) HTML (0) PDF (0.00 ByteKB)(0)

  Abstract:

  In view of the high carbon number of paraffin wax in Yingmai crude oil of Tarim Oilfield，the poor effect of conventional oil-soluble paraffin inhibitor and the difficulty of filling due to the high viscosity at low temperature，an ultra-long carbon chain ternary polymer DMS was prepared by free radical solution polymerization using docosyl acrylate，maleic anhydride and styrene as raw materials，which was suitable for preventing wax deposition in high carbon wax crude oil. The preparation conditions and anti-wax properties of emulsion anti-wax agent HDMS with DMS as dispersed phase and deionized water as continuous phase were emphatically discussed. The results showed that when the mass ratio of T-80 to S-80 was 7∶3 and the composite emulsifier dosage was 10%，the prepared HDMS had good fluidity at 10 ℃ and the viscosity was 24.65 mPa·s. HDMS had good dispersion stability after standing at room temperature for 28 d. The particle size of HDMS was about 2200 nm and the amount of dehydration was only 0.6 mL（the bulk volume was 80 mL）within 1—28 d. When the action temperature was 60 ℃，the action time was 80 min，and the HDMS dosage was 2000 mg/L，the wax prevention rate of HDMS for high-carbon waxy crude oil was up to 84% and had certain wax prevention universality.

• Efficiency of Microalgae-bacteria Treatment of Oilfield Produced Water and Domestic Sewage

  LI Ran, LI Tong, WANG Liangliang, ZHAO Jin, PAN Jie

  2025,42(1):148-153, DOI: 10.19346/j.cnki.1000-4092.2025.01.020

  Abstract: (82) HTML (0) PDF (0.00 ByteKB)(0)

  Abstract:

  Oilfield produced water has a high concentration of pollutants and lacks elements such as N and P needed for biological growth. Domestic sewage is rich in N and P，but the discharge fluctuates greatly，and the cost of separate treatment is high. In order to improve the biological treatment efficiency and reduce the treatment cost of oilfield sewage，the simulated oilfield produced water was mixed with the simulated domestic sewage for microalgae-bacteria symbiosis culture，and then the effects of different volume mixing ratios of produced water and domestic sewage（1∶3，1∶5，1∶15，1∶35）on the growth of organisms and the removal of nutrients were investigated. The microalgae was Chlorella vulgaris，while the strains were composed of Saccharomyces cerevisiae，Lactobacillus，Nitrobacter and Bacillus subtilis. The results showed that the biomass，algal density，bacterial density and chlorophyll of different ratios of produced water/domestic sewage mixtures basically presented an increasing trend with the increase of incubation time. Microalgae-bacteria grew best in the produced water/domestic sewage mixture with a mixing ratio of 1∶3. The total biomass was 0.55 g/L after 7 d of incubation，of which the algal density was 0.23 g/L and the bacterial density was 0.32 g/L. The high ratio of produced water/domestic sewage mixture was favorable for the growth of algae. The highest content of algal chlorophyll a was 649.27 μg/mg after 7 d of incubation in the produced water/domestic sewage mixing ratio of 1∶3，while the highest content of algal chlorophyll b was 821.23 μg/mg in the mixing ratio of 1∶5. In the aspect of nutrient removal，the sewage with a high mixing ratio was more favorable for the nutrient absorption by microalgae-bacteria. The highest removal rates of organic matter and ammonia-nitrogen were obtained when the mixing ratio of produced water and domestic sewage was 1∶3. Meanwhile， the removal rate of chemical oxygen demand（COD）was 65%，and that of ammonia-nitrogen was 37%. The water sample with a mixing ratio of produced water and domestic sewage of 1∶5 had the best removal of total phosphorus，with a removal rate of 70%. Mixing oilfield produced water and domestic sewage in appropriate volume ratio could promote the growth of algae-bacteria and improve the efficiency of biological treatment.

• Simultaneous Determination of Three Residual Monomers in Water-soluble Polymer by HPLC

  LIU Huasha, LI Jingjing, LIU Sijia, SUN Qiang

  2025,42(1):154-158, DOI: 10.19346/j.cnki.1000-4092.2025.01.021

  Abstract: (92) HTML (0) PDF (0.00 ByteKB)(0)

  Abstract:

  As for the problem that the detection method of residual monomer of water-soluble polymer was too targeted，a method for simultaneous determination of maleic acid，fumaric acid and itaconic acid in water-soluble polymer used in drilling fluid by HPLC was established. The experimental conditions were obtained as follows：the water-soluble polymer was extracted with acetonitrile for 30 min，and the mobile phase contained 0.1% phosphoric acid and acetonitrile at volume ratio 85∶15. Agilent Zorbax Eclipse XDB C18 column（250 × 4.6 mm，5 μm）was used，and the flow rate of column was 0.8 mL/min，the column temperature was 45 ℃，and the detection wavelength was 210 nm. Under the above experimental conditions，the detection results had good separation characteristics（the separation degree was greater than 3），good linear relationship（the R² value was greater than 0.999）and good stability（the RSD was less than 1%）. The minimum detection limit of maleic acid，fumaric acid and itaconic acid were 0.32，0.34 and 0.63 mg/kg. the quantitation of maleic acid，fumaric acid and itaconic acid were 1.21，1.26 and 2.02 mg/kg. The recoveries of the three residual monomers were 98%—101%. The mass fractions of the three residual monomers in a sample of the viscosifier were 2.261%，0.284% and 2.775%. The time of chromatographic detection was less than 10 min，and it could meet the quality control of the water-soluble polymer. The method could accurately control the synthesis process of water-soluble polymers and achieve accurate quality control.

• Research and Application Progress of pH Responsive Materials for Oil and Gas Drilling

  WANG Junping, CAO Qingtian

  2025,42(1):159-166, DOI: 10.19346/j.cnki.1000-4092.2025.01.022

  Abstract: (96) HTML (0) PDF (0.00 ByteKB)(0)

  Abstract:

  With the acceleration of domestic oil and gas field development，it is difficult for traditional oilfield chemical materials to adapt to the increasingly complicated underground working environment. However，pH-responsive materials can respond under the stimulation of underground acid-base environment，so as to change their own structure and surface properties，and then better adapt to underground environment to meet the needs of oil and gas drilling and production operations. This paper briefly analyzes the action mechanism of pH responsive materials，and reviews the response mechanism and research status of pH responsive materials based on surfactants and polymers in drilling fluids，chemical flooding and fracturing fluids.

• Research Progress of Polymer Gel Profile Control and Plugging Agent in High Temperature and High Salinity Reservoirs

  GUO Hongyu, ZHAO Chenkang, ZU Yu, JIANG Wei, LIU Yanfeng, WANG Dongjun, GUO Jintao, WANG Weizhong

  2025,42(1):167-173, DOI: 10.19346/j.cnki.1000-4092.2025.01.023

  Abstract: (119) HTML (0) PDF (0.00 ByteKB)(0)

  Abstract:

  Fine tapping of old oil fields is a key means of stabilizing the crude oil production. The main old oil fields are generally in the middle and late stages of "double high" development，with great difficulty in stabilizing production，especially in high temperature and high salinity formations. The existing plugging agent technology is difficult to solve problems such as high water content and formation heterogeneity. Based on the harsh conditions of high temperature and high salinity formation and the limitations of existing technologies，this paper introduces the research and application of modified polyacrylamide gel，silica polymer gel，slow cross-linking polymer gel and biological based profile control and plugging gel system at home and abroad，and focuses on the slow cross-linking polymer gel system，slow cross-linking technology and influencing factors. Among the above gels，PEI polymer gel has strong reliability and wider application range，however，with tightening of environmental protection policies，bio-based polymer gel plugging agent is the main development trend in the future.

• Research Progress of Foam System Stabilized by Nanoparticles for Oil Flooding

  LIANG Xiaotian, ZHANG Jingnan, LI Bin, LI Meng, SHI Yan, WU Chao

  2025,42(1):174-181, DOI: 10.19346/j.cnki.1000-4092.2025.01.024

  Abstract: (110) HTML (0) PDF (0.00 ByteKB)(0)

  Abstract:

  To address the issue of poor stability in conventional foam systems during oil flooding，nanoparticles are utilized to stabilize foams. For foam systems stabilized by nanoparticles used in oil flooding，based on the main components of the system formulas，they could be categorized into three types：nanoparticle foaming system，nanoparticle-surfactant foaming system，and nanoparticle-surfactant-polymer foaming system. The characteristics of different types of nanoparticles in stabilizing foams were analyzed. Based on this，it was pointed out that the development of nanoparticle-stabilized foam systems for oil flooding should move towards diversity，functionality，high performance，low cost，environmental friendliness and recyclability. Currently，the development of nanoparticle-stabilized oil flooding foam systems mainly relied on extensive experiments. Further research was needed on the microscopic mechanism of nanoparticle-stabilized foam. It should establish parameters that could quantitatively describe the factors affecting foam stability，and then realize the functional customization of new foam systems. Thus，the nanoparticle-stabilized foam systems could be applied to different reservoirs or various extraction fields.

• Study Progress on Mechanism and Influencing Factors of Asphaltene Precipitation Inhibition by Nanoparticles

  HAN Yuxiao, DENG Shuyuan, WANG Bo, WU Qijun, FU Jian, SHE Yuehui, ZHANG Fan

  2025,42(1):182-190, DOI: 10.19346/j.cnki.1000-4092.2025.01.025

  Abstract: (95) HTML (0) PDF (0.00 ByteKB)(0)

  Abstract:

  Asphaltene precipitation is a common challenge in the petroleum industry，occurring across nearly every stage of oil production，processing and transportation，often leading to serious operational problem. Nanoparticles（NPs），as a novel class of materials，possess exceptionally high surface energy due to their unique properties，including small size，surface effect，and quantum size effect，making them highly effective in adsorption and catalysis applications. This paper explored the mechanisms by which NPs inhibit asphaltene precipitation，including adsorption stabilization and steric hindrance. The potential action modes of each mechanism were also elaborated. Furthermore，the factors influencing the effectiveness of NPs in inhibiting asphaltene precipitation were reviewed，including nanoparticle factors，asphaltene properties and medium characteristics. The underlying mechanisms of these factors were analyzed，along with the synergistic or antagonistic interactions among them.

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

  ZHAO Kaiqiang

  Abstract: (85) HTML (0) PDF (0.00 ByteKB) (100)

  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: (125) HTML (0) PDF (0.00 ByteKB) (77)

  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: (172) HTML (0) PDF (0.00 ByteKB) (93)

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

  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: (492) HTML (0) PDF (0.00 ByteKB) (169)

  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: (395) HTML (0) PDF (0.00 ByteKB) (685)

  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: (569) HTML (0) PDF (0.00 ByteKB) (711)

  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: (626) HTML (0) PDF (0.00 ByteKB) (850)

  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: (623) HTML (0) PDF (0.00 ByteKB) (891)

  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: (424) HTML (0) PDF (0.00 ByteKB) (801)

  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: (489) HTML (0) PDF (0.00 ByteKB) (862)

  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: (423) HTML (0) PDF (0.00 ByteKB) (802)

  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: (609) HTML (0) PDF (0.00 ByteKB) (1000)

  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: (588) HTML (0) PDF (0.00 ByteKB) (846)

  Abstract:

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

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

  WANG Hongbo, MA Ting

  Abstract: (337) HTML (0) PDF (0.00 ByteKB) (1057)

  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: (1312) HTML (0) PDF (0.00 ByteKB) (1241)

  Abstract:

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

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

  SHEN Xiulun

  Abstract: (742) HTML (0) PDF (0.00 ByteKB) (1537)

  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: (432) HTML (0) PDF (0.00 ByteKB) (1111)

  Abstract:

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

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

  Fu Hong

  Abstract: (511) HTML (0) PDF (0.00 ByteKB) (835)

  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: (329) HTML (0) PDF (0.00 ByteKB) (806)

  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: (309) HTML (0) PDF (0.00 ByteKB) (778)

  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: (441) HTML (0) PDF (0.00 ByteKB) (790)

  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: (331) HTML (0) PDF (0.00 ByteKB) (840)

  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: (343) HTML (0) PDF (0.00 ByteKB) (862)

  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: (384) HTML (0) PDF (0.00 ByteKB) (978)

  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: (455) HTML (0) PDF (0.00 ByteKB) (871)

  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: (447) HTML (0) PDF (0.00 ByteKB) (837)

  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: (455) HTML (0) PDF (0.00 ByteKB) (858)

  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: (444) HTML (0) PDF (0.00 ByteKB) (924)

  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: (397) HTML (0) PDF (0.00 ByteKB) (891)

  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.

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

  Chen Liang, You Fu-chang.

  Abstract: (272) HTML (0) PDF (0.00 ByteKB) (966)

  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: (449) HTML (0) PDF (0.00 ByteKB) (1036)

  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.

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

  JIANG Huixin, WANG Chuangye

  Abstract: (305) HTML (0) PDF (0.00 ByteKB) (1297)

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

  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: (370) HTML (0) PDF (0.00 ByteKB) (931)

  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: (385) HTML (0) PDF (0.00 ByteKB) (897)

  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: (267) HTML (0) PDF (0.00 ByteKB) (973)

  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: (469) HTML (0) PDF (0.00 ByteKB) (1009)

  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: (385) HTML (0) PDF (0.00 ByteKB) (939)

  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: (436) HTML (0) PDF (0.00 ByteKB) (933)

  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: (374) HTML (0) PDF (0.00 ByteKB) (967)

  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: (479) HTML (0) PDF (0.00 ByteKB) (1281)

  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: (471) HTML (0) PDF (0.00 ByteKB) (1052)

  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: (347) HTML (0) PDF (0.00 ByteKB) (1015)

  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: (300) HTML (0) PDF (0.00 ByteKB) (1023)

  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: (567) HTML (0) PDF (0.00 ByteKB) (1011)

  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: (366) HTML (0) PDF (0.00 ByteKB) (1037)

  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: (1080) HTML (0) PDF (0.00 ByteKB) (1020)

  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: (243) HTML (0) PDF (0.00 ByteKB) (939)

  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: (264) HTML (0) PDF (0.00 ByteKB) (976)

  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: (526) HTML (0) PDF (0.00 ByteKB) (1058)

  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: (343) HTML (0) PDF (0.00 ByteKB) (962)

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

  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: (353) HTML (0) PDF (0.00 ByteKB) (1020)

  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: (795) HTML (0) PDF (0.00 ByteKB) (1078)

  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: (658) HTML (0) PDF (0.00 ByteKB) (1045)

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

  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: (526) HTML (0) PDF (0.00 ByteKB) (1059)

  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: (394) HTML (0) PDF (0.00 ByteKB) (1097)

  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: (492) HTML (0) PDF (0.00 ByteKB) (1307)

  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: (463) HTML (0) PDF (0.00 ByteKB) (1027)

  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: (455) HTML (0) PDF (0.00 ByteKB) (988)

  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.

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

  Liang Yukai, Yu Xiaocong

  Abstract: (305) HTML (0) PDF (0.00 ByteKB) (918)

  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: (822) HTML (0) PDF (0.00 ByteKB) (1038)

  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: (346) HTML (0) PDF (0.00 ByteKB) (1021)

  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: (358) HTML (0) PDF (0.00 ByteKB) (1014)

  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: (715) HTML (0) PDF (0.00 ByteKB) (1052)

  Abstract:

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

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

  Li Yikun

  Abstract: (541) HTML (0) PDF (0.00 ByteKB) (1063)

  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.

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

  Ma Tengfei, Zhou Yu

  Abstract: (652) HTML (0) PDF (0.00 ByteKB) (1061)

  Abstract:

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

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

  ZHANG Ying, YU Weichu

  Abstract: (634) HTML (0) PDF (0.00 ByteKB) (995)

  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: (559) HTML (0) PDF (0.00 ByteKB) (1007)

  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: (568) HTML (0) PDF (0.00 ByteKB) (1115)

  Abstract:

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

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• water-soluble resin-based cementing fluid system

  HE Yingzhuang, YAN Siming

  Abstract: (354) HTML (0) PDF (0.00 ByteKB) (1222)

  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: (406) HTML (0) PDF (0.00 ByteKB) (1053)

  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: (576) HTML (0) PDF (0.00 ByteKB) (1083)

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

  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: (594) HTML (0) PDF (0.00 ByteKB) (1331)

  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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• Application of Microfluidic Technology in Nano-Oil Displacement

  YAN Shi, Hou Changbing, FU Jian, WANG Zekun, SHE Yuehui, SUN Shanshan, ZHANG Fan

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

  Abstract:

  Since the introduction of microfluidic technology, its application has spanned many disciplines and fields. Among them, the micro-displacement technology using visual micro-model to simulate real reservoir rock pores has shown extraordinary application value and development potential in recent years. Compared with the traditional macroscopic core flooding experiment, this method shows many advantages. In particular, it realizes the visualization of multiphase flow in pores so that researchers can study the microscopic mechanism of oil displacement. Nano-oil displacement method has been widely concerned and applied in tertiary oil recovery in recent years. The unique physical and chemical properties brought by the small size of nanoparticles make them play a role in various mechanisms in rock pores. By combing the microscopic nano-oil displacement experiments carried out by many scholars using microfluidic equipment in recent years, the microscopic mechanism of nano-oil displacement mainly includes : wettability change, reduction of interfacial tension (IFT), improvement of mobility ratio, and stabilization of asphaltene. At the same time, the main control parameters affecting the effect of nano-oil displacement are summarized. With the development and improvement of related technologies, the application of microfluidic methods provides a more advantageous platform for the exploration of the microscopic mechanism of nano-oil displacement and the optimization of control parameters.

  • 1
• Experimental study on the influence of Ca2+ on the ultra-low interfacial tension of petroleum sulfonate solution

  王雨, Lin Lili, Wu Yonghua, Wang Xinghua

  Abstract: (16) HTML (0) PDF (0.00 ByteKB) (0)

  Abstract:

  In the binary composite flooding technology, studying the micro-mechanism of the influence of Ca2+ on ultra-low interfacial tension can provide reference for surfactant formulation optimization. By measuring the interfacial characteristic parameters of petroleum sulfonate KPS, such as the solubility product constant Ksp, surface tension, interfacial tension, and partition coefficient, the main conditions for KPS to form ultra-low interfacial tension were clarified. The results show that the influence of Ca2+ on the surface tension of the KPS solution is related to the decrease in the polarity of the micellar microenvironment. For the KPS system prepared with de-calcium water, exhibited two-order-of-magnitude higher IFT compared to calcium-containing solutions, with IFT restoration observed upon reintroducing 40 mg/L Ca2+. Partition coefficient analysis in 0.3% KPS/kerosene systems demonstrates that 40 mg/L Ca2+ induces optimal surfactant distribution (K=0.101) with molecular minimum occupied area (Amin) reaching 0.58 nm2. At this time, the sum of the concentrations of KPS in the two phases is less than the total concentration, and the “excess” KPS molecules are concentrated in the interfacial layer. A novel "interfacial complexation" model is proposed, suggesting that Ca2+ bridges two sulfonate groups (-SO3-) near the oil-water interface, which is further validated through disodium phthalate solution experiments. These findings provide molecular-level insights into cation-mediated interfacial activity modulation in enhanced oil recovery systems.

  • 1
• Determination method of polymer concentration and viscosity relationships in numerical simulation of polymer flooding

  Li Le-zhong, Tang En-gao, Jin Yi, Xia An-long, Sun Xiao-fei

  Abstract: (20) HTML (0) PDF (0.00 ByteKB) (0)

  Abstract:

  Due to factors such as shear in porous media of oil reservoirs, the viscosity concentration relationship of polymers obtained by experimental methods is difficult to directly apply to numerical simulations. At present, the commonly used empirical or analogical methods have large errors, and there is still a lack of effective numerical simulation methods for determining the viscosity concentration relationship in polymer flooding. Therefore, this article designs to conduct experiments on the influence law of polymer flooding, establish a numerical simulation model of polymer flooding core to fit the experimental results, determine the viscosity concentration relationship of polymer flooding numerical simulation under different temperature, mineralization and permeability conditions, establish a prediction model for adjusting the viscosity concentration relationship of polymer flooding, and thus form a method for determining the viscosity concentration relationship of polymer flooding numerical simulation. Research has shown that using the proposed method to determine polymer viscosity concentration relationship data, the fitting error of polymer flooding water content is 1.81%, which is 7.42% lower than existing empirical methods, improving the accuracy of polymer flooding numerical simulation and providing reliable parameters and references for polymer flooding numerical simulation.

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• Research progress and application of salt crystallization inhibitors

  SUN Dongzheng, GENG Tie, WANG Chaoqun, ZHANG Yufei, REN Jintian, GUO Jiabao, ZHANG Conghan, YANG Fan

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

  Abstract:

  With the rapid development of high density brine drilling and completion fluid technology, it has become a hot spot of technology development and application in the field of deep oil and gas well development. The preparation of high-density brine requires the use of various expensive weighted salts, which greatly increases the cost of high-density brine drilling and completion fluids. The use of salt crystallization inhibitors can effectively overcome this problem. By regulating the balance between salt solution dissolution and crystallization, it can effectively suppress wellwall scaling and improve the density of saline drilling and completion fluids. The related mechanism and current development status of salt crystallization inhibitors are discussed to provide theoretical basis for the development of new salt solubilizers with high performance and low cost. Based on the preliminary search of Chinese and English databases, the action mechanisms of salt crystallization inhibitors are divided into complex solubilization mechanism, micellar solubilization mechanism, dispersion mechanism and lattice distortion mechanism. Salt crystallization inhibitors can be classified into copolymers, surfactants, natural organic molecules and their derivatives. Further search for literatures with strong correlation, introduce the development process of various salt crystallization inhibitors respectively, and construct a research and development material library for the development of new salt solubilizing solvent for the preparation of high-density salt water from solubilizing salt. At present, there are only 6 reports on salt crystallization inhibitors used for solubilizing salt to prepare high-density saline drilling fluids, and the main ones are surfactant salt crystallization inhibitors and copolymer salt crystallization inhibitors. In the field of scale inhibition, new high-performance salt crystallization inhibitors, including tree copolymers, green copolymers, natural organic molecules and derivatives, have been developed successively, which provides development experience and methods for the development of new salt crystallization inhibitors for solubilization.

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• Preparation and Performance Evaluation of Temperature- and Salt-Tolerant Quantum Dot-Based Oil Displacing Agents for Low Permeability Oil Reservoirs

  LU Xiaobin, YAN Ruoqing, YANG Lian, LIU Yulong, WAN Qifeng

  Abstract: (37) HTML (0) PDF (0.00 ByteKB) (0)

  Abstract:

  In response to the problem of the development of micro-nano pore throats in low-permeability reservoirs, the difficulty in the stripping and activation of crude oil, and the difficulty in utilization, a quantum dot oil displacement agent was synthesized and characterized, and its performance was evaluated. Carbon-silicon quantum dot materials were synthesized by solvent evaporation and thermal decomposition, and then purified, dried and ultrasonically dispersed in pure water to form the product. The material was characterized. TEM showed that the quantum dots were spherical with a particle size of about 4 nm and good dispersion. XRD identified the (002) crystal plane of carbon and the (111) crystal plane of silicon, which were in an amorphous state. FT-IR indicated that the surface of the quantum dots contained hydroxyl, carboxyl and amino groups, which could form hydrogen bonds with water molecules, improving the stability of the fluid. The performance of the quantum dot oil displacement agent was evaluated. Under the conditions of 135℃ and 300,000 salinity, the fluorescence spectrum did not change significantly. At a concentration of 0.3%, the interfacial tension could be reduced to 0.92 mN/m, and the rock surface wettability could be changed to water-wet. The ability to enhance oil recovery was evaluated by low-permeability core experiments. The experiments showed that the imbibition efficiency of the quantum dot oil displacement agent was as high as 47.4%, more than twice that of the simulated formation water. NMR T2 spectra identified that the quantum dots could reach the micro-pores (1-10 ms), and the core displacement recovery rate increased by 22%. The carbon-silicon quantum dot oil displacement agent developed in this research has a significant effect on enhancing oil recovery in low-permeability reservoirs, with broad research prospects, providing a good reference for the efficient development of oil fields.

  • 1
• The Sealing Property and Adaptability of Temperature and Salt Resistant Resin Gel in Fractured-Vuggy Cells

  ZHAO Yuheng, QU Ming, SUN Haitong, WANG Jun, WU Waipeng, YANG Min, LIANG Tuo, HOU Jirui, ZHAO Yu

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

  Abstract:

  To investigate the effectiveness of temperature and salt resistant resin gel in enhancing remaining oil recovery during the late-stage waterflooding development of typical fractured-vuggy carbonate reservoirs in the Tahe Oilfield, a macro-visualization physical model meeting similarity criteria was designed and constructed. Based on this model, a comparative study was conducted to evaluate the plugging performance of the resin gel and its impact on remaining oil recovery in three types of fractured-vuggy reservoirs. The results showed that the temperature and salt resistant resin gel exhibits good injectivity under conditions of 150℃ and 252,903 mg/L salinity. In sandy-silt models, the gel mainly distributes along the walls in an aggregated pattern, while in collapsed-filling and loosely-packed models, it shows continuous and uniform distribution. The gel can induce flexible fluid diversion in the reservoir and provide effective cementation and plugging of internal media and fracture channels. Furthermore, the temperature-resistant and salt-tolerant resin gel demonstrates significant post-waterflood enhancement, increasing recovery factors by 18.61, 18.13, and 13.64 percentage points in sediment filling, collapse fracture cavity, and loose filling models respectively, while maintaining plugging efficiencies exceeding 98% in all scenarios. The research shows that the temperature-resistant and salt-tolerant resin gel exhibits excellent plugging performance and enhanced oil recovery effectiveness across various fractured-vuggy structures, showing robust adaptability that provides reliable technical support for field applications.

  • 1
• Synthesis and performance evaluation of Gemini Maleic anhydride octylphenol polyethylene ethyl ether diesters

  CAO Zhezhe, WANG Qiuxia, WANG Hongyu, MIAO Jialin, YAN Jinlun, ZHANG Longli

  Abstract: (20) HTML (0) PDF (0.00 ByteKB) (0)

  Abstract:

  Gemini surfactant is known as "a new generation of surfactants" and has great commercial value. In this paper, Gemini type octylphenol polyoxyethylene ether surfactant was synthesized by one step reaction, and the reaction conditions were optimized. The surface tension, interfacial tension, wettability, emulsification and viscosity reduction properties of a series of Gemini surfactants synthesized under the optimal reaction condition of 200℃, 6h and molar ratio of 2:1 were evaluated. Gemini surfactant has lower critical micelle concentration (CMC), better oil washing and viscosity reduction effects than ordinary surfactant. The CMC value of Gemini octylphenol polyoxyethylene ether surfactant (MOP-10) was 0.052mmol/L and the interface tension was 8.04 ×10_-2 ^mN/m, both of which were an order of magnitude lower than that of ordinary surfactant OP-10. Gemini type octylphenol polyoxyethylene ether with the increase of ethoxy group, CMC value gradually decreased, surface tension, interfacial tension gradually increased, oil washing viscosity reduction effect became worse. The synthetic route is simple, the raw material source is wide and the price is low. It can be used as an intermediate product to synthesize a variety of surfactants or polymers, providing a new raw material for the development of surfactants and the modification of polymers.

  • 1
• Development and Evaluation of Pressure Sensitive Self-healing Plugging Agent for Drilling Fluid

  CHU Qi, JIN Bingyao, LIU Haijun, ZHANG Maowen, TIAN Yachuan, WANG Lifeng

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

  Abstract:

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

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• Preparation and performance evaluation of self-healing hydrogel based on CMC@Fe₃O₄ dual network

  ZHOU Xianggang, HE Long, HUANG Xueli, WANG Nan, WU Gang

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

  Abstract:

  Conventional oilfield plugging agent in the deep water plugging of oil wells is prone to degradation and failure, and the volume expansion of the plugging agent is very easy to be damaged after the absorption of liquid to lose the plugging effect, it is difficult to meet the needs of deep water plugging, and it is necessary to design a self-repairing performance of deep blocking agent. Based on the physical crosslinking network of CMC@Fe3O4, the physicochemical dual network self-repairing hydrogel P(AM/AMPS/NVP)/CMC@Fe3O4 was constructed by using the three monomers of AM, AMPS and NVP as the copolymer, KSP as the initiator, and hydroquinone (HQ) and hexamethylenetetramine (HMTA) as the crosslinking agent, and the self-repairing performance and temperature and salt resistance were characterised. The optimum formulation of this self-healing gel system was 92 wt% CMC@Fe3O4 dispersion, 5.6 wt% AM, 2.4 wt% AMPS, 0.4 wt% NVP, pH= 9, the initiator KSP was 0.8 wt% by mass of the monomer, and the cross-linkers were 0.6 wt% HQ and 0.6 wt% HMTA. The modulus of elasticity G" was 230.6 Pa. The 30-day aging dehydration rate was 6.2137% at a high temperature of 130℃and a high mineralisation of 2.2×10⁵ mg/L stratum. The gel was aged in an oven at 130℃ for 1 h to achieve self-repair, with a gel fracture elongation of 375% and a repair efficiency of 100%.

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• Discussion on the mechanism of nano-modification and its effect on the efficiency of seepage and suction oil drive

  Zhang Xinyue, Tang Shanfa, Hu Hao, Wang Zhe, Dong Yuanwu, Chen Zequn

  Abstract: (30) HTML (0) PDF (0.00 ByteKB) (0)

  Abstract:

  In order to solve the problems of low porosity, low permeability, strong heterogeneity, complex geological conditions and high exploitation difficulty in tight reservoirs, Janus nano-SiO2 with amphiphilic properties (sulfonic acid group on one side and n-octyl group on one side) was prepared, and its properties before and after modification were compared and analyzed by infrared spectroscopy, scanning electron microscopy, zeta potential and particle size determination. At the same time, the interfacial tension and wettability performance tests were used to simulate the oil sorption and flooding effects of Janus nano-SiO2 particles under different conditions. The results showed that the final recovery degree of Janus nano-SiO2 particles was 8.6% higher than that of unmodified nano-SiO2 particles. At a concentration of 0.05wt%, the final recovery degree reached 25.71%. It can be seen that the amphiphilic Janus nano-SiO2 not only significantly improves the performance of nanomaterials in the process of imbibition and flooding, but also effectively improves the recovery degree of crude oil, and provides a new cost-effective strategy for improving oil recovery in oilfields, which has important practical guiding significance.

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• Development and evaluation of a novel sustained self-heating energy-enhancing oil-displacement fracturing fluid system

  FAN Jiacheng, SHU Qinglin, ZHAI Liang, LIU Haicheng, JIA Yanping, LIU Xiaoying, TAO Shiyu, SUN Chenglong

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

  Abstract:

  Hydraulic fracturing has become a crucial technology for developing shallow ultra-low permeability conventional heavy oil reservoirs in Shengli Oilfield. To address the challenges of low reservoir temperature and high oil viscosity, self-heating fracturing fluids were proposed, which utilize exothermic reactions to enhance fluid mobility, remove organic blockages, and reduce oil viscosity. However, conventional self-heating systems initiate reactions during surface mixing, causing heat and gas loss during injection. Additionally, the high surface tension of fracturing fluids results in poor sweep efficiency in low-permeability reservoirs. To overcome these limitations, we developed an innovative sustained self-heating energized oil-displacement fracturing fluid system based on the exothermic reaction between urea and sodium nitrite in hydrochloric acid solution. By incorporating both free-state and water-in-oil emulsified HCl, the system achieves dual-stage heat generation during and 40 minutes after injection, reaching temperatures above 80°C, thereby effectively heating the fluid, near-wellbore zones, and distal fractures. Furthermore, through the addition of a synthesized low-molecular-weight polymeric surfactant, we reduced the fluid's surface tension to 25 mN/m and achieved ultra-low interfacial tension of 0.0008 mN/m with crude oil, significantly improving sweep efficiency and oil recovery to meet the development requirements of shengli oil field's low-permeability reservoirs.

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

  Xu Lin, Zhao Nan, Xu Changfeng, Su Huaiyu, Wang Jianjun, Yang Siqi, Li Zhiyuan, Han Xu, Gao Yang

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

  Abstract:

  Hyperbranched polymers, with their unique three-dimensional topological structures and abundant active terminal groups, have shown significant potential in enhancing the lubricating properties of water-based drilling fluids. However, the structure-activity relationship between their molecular configurations and lubricating performance remains unclear, which hinders the development of new high-performance additives based on spatial configuration design. This study, based on the boundary lubrication model of hyperbranched polymers, focuses on polyamidoamine (PAMAM) as the research subject. Using quantum chemical and molecular dynamics methods, the structural characteristics of multi-generation (G1-G5) PAMAM molecules and their adsorption behavior on iron (Fe) surfaces were systematically investigated at the molecular scale. Additionally, the structural changes of PAMAM molecules on Fe surfaces during shear processes were analyzed. The results indicate that: (1) PAMAM hyperbranched macromolecules possess hierarchically distributed N and O active atoms, with the central N atom exhibiting the strongest electron-donating ability, followed by the terminal N atoms; (2) as the generation increases up to G5, the three-dimensional structural stability of PAMAM molecules improves, with enhanced entanglement of molecular chains at the core and "claw-like" distribution of outer branches, which enhances multi-point adsorption capabilities; (3) during the adsorption of PAMAM molecules on Fe surfaces, atomic distribution extends along the interface and its normal direction, while shear promotes the aggregation of PAMAM molecules at the Fe interface, forming a transfer film that contributes to the formation of a robust lubricating layer. Finally, a lubrication enhancement model for hyperbranched polymers is proposed, which should provide theoretical support for the design of high-performance hyperbranched polymer additives.

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• Study on Adjusting Integrated Measures by Combining Secondary and Tertiary Recovery Methods in the Songfangtun Peripheral Oilfield

  ZHOU Zhijun, Zhangqi

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

  Abstract:

  The Fang-2 Block is located in the peripheral oilfield of Songfangtun and has currently entered a high water-cut development stage. The main challenges faced by this block include poor water flooding control efficiency, a high proportion of low-production wells, and a significant number of long-term shut-in wells. The traditional inverted nine-spot well pattern is no longer suitable for meeting the requirements of efficient extraction. To address these issues and enhance the recovery rate of the block, this study proposes a new development strategy through a combination of laboratory experiments and reservoir numerical simulation. The proposed strategy involves optimizing the existing well pattern into a five-spot configuration and adjusting the well spacing to 195.1 meters. Additionally, considering the geological characteristics of the low-permeability reservoir in the Fang-2 Block, the middle-phase microemulsion flooding technology is introduced to further improve development efficiency. Experimental results indicate that the optimal system performance is achieved when SB-12 and SJ-1 are mixed at a mass ratio of 1:3 as the core surfactants for the middle-phase microemulsion, with a mass fraction of 0.5%. The optimal mass fraction of n-butanol as a co-surfactant, determined through alcohol scanning, is 9.4%, and the optimal salinity is 4.3% NaCl. In sand-packed model flooding experiments, the injection of middle-phase microemulsion increased the oil displacement efficiency by 24.65%. Furthermore, predictions based on CMG numerical simulation software suggest that when the water cut reaches 86%, the injection of middle-phase microemulsion can enhance the recovery factor by 20.42%, with an estimated cumulative incremental oil production of 319,300 tons. The findings of this study not only provide an effective technical approach for the development of the Fang-2 Block in the Songfangtun peripheral oilfield but also offer significant theoretical and practical references for the development of other continental low-permeability reservoirs.

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• WANG Y F. The exploration and development of unconventional oil and gas resources in China has broad prospects[J]. Petroleum Knowledge, 2021, (6): 14-15.[2] Zhang W. Technology of water injection development in ultra-low permeability reservoir[C].//IOP Conference Series: Earth and Environmental Science. IOP Publishing, 2020, 558(2): 1315-1755.

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

  Abstract: (49) HTML (0) PDF (0.00 ByteKB) (0)

  Abstract:

  In order to clarify the basic properties of the novel C-Si quantum dots and their applicability in low-ultra-low permeability reservoirs, this paper first conducts a test and analysis of the interfacial properties and compatibility of the novel C-Si quantum dot oil-displacement agent. Subsequently, core imbibition and displacement experiments are carried out to explore the macroscopic imbibition oil-displacement characteristics of the quantum dots. Finally, nuclear magnetic resonance analysis and microscopic model experiments are used to reveal the oil-displacement characteristics of the quantum dots at the microscopic level. The results show that the quantum dot oil-displacement agent has the ability to change the core surface to hydrophilicity. Meanwhile, it exhibits strong negative charge, as well as good temperature and salt resistance. When the concentration of the quantum dot oil-displacement agent is 0.5%, the imbibition oil-displacement effect is the best, with the imbibition efficiency reaching as high as 48.5%. It also shows a continuous effect during the core displacement process. The quantum dots have a small particle size, more intense Brownian motion, and can easily enter tiny pores. The imbibition efficiency in the tiny pores (1-10 ms) of the core can reach 30%. The quantum dots expand the sweep range of the water phase by weakening the hydrogen-bond association of water molecules, and can 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-ultra-low permeability reservoirs using the quantum dot oil-displacement agent.

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• A new method for monitoring the photocatalytic degradation of polyacrylamide gel used in oil fields

  XU Hui, SUN Xiuzhi, GONG Jincheng, SONG Min, LIANG Xiaojing

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

  Abstract:

  Polyacrylamide polymers are extensively employed in tertiary oil recovery and have demonstrated significant improvements in oil recovery efficiency. However, this process generates substantial quantities of oil recovery wastewater containing high concentrations of polyacrylamide, which pose environmental risks if discharged untreated. Photocatalytic degradation offers a promising solution for treating this wastewater. Yet, current monitoring methods for assessing polymer degradation exhibit notable shortcomings in terms of sensitivity, accuracy, and reproducibility. To address the aforementioned challenges, this paper introduces a swift, precise, and comprehensive method for monitoring polymer photocatalytic degradation. This is achieved through the integration of liquid chromatography and mass spectrometry to evaluate the degradation process of two distinct polyacrylamide gels utilized in oil fields. Liquid chromatography allows for the observation of transition products with high molecular weights during th

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• Preparation of amino acid derivative corrosion inhibitor and its corrosion inhibition performance in HCl environment

  XU Yingbiao, WANG Yefei, JIN Kai, WANG Tingyi, ZHANG Lingyu, TANG Longhao

  Abstract: (59) HTML (0) PDF (0.00 ByteKB) (0)

  Abstract:

  A polar group substituted imidazole zwitterionic liquid was synthesized by glycine. The results of IR and NMR showed that imidazole ring structure was present in the synthesized corrosion inhibitor. An investigation into the corrosion inhibition of N80 steel in 1 M Hydrochloric acid solution at 25℃ was conducted using both weight loss and electrochemical techniques. The findings indicate that the adsorption behavior of the amphoteric corrosion inhibitor conforms to the Langmuir adsorption isotherm, with a combination of both physical and chemical adsorption occurring on the steel surface. As the quantity of the inhibitor increases, its corrosion inhibition efficiency rises accordingly. Specifically, at a concentration of 50 mg/L, the efficiency is 91.29%, and it further increases to 93.92% at 200 mg/L. Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) results reveal that the inhibitor smooths the steel surface and diminishes corrosion pits. Additionally, X-ray Photoelectron Spectroscopy (XPS) analysis confirms the formation of Fe-N bonds on the N80 steel surface after immersion in the inhibitor solution, suggesting the presence of an adsorbed protective film on the metal. The amino acid corrosion inhibitor synthesized in this paper provides an effective strategy for corrosion protection of steel under high acid environment.

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• The effect of reservoir heterogeneity on oil recovery and distribution by CO₂ continuous and huff-n-puff injection

  ZHANG Jianning, LI Lifeng

  Abstract: (60) HTML (0) PDF (0.00 ByteKB) (0)

  Abstract:

  Due to a good injectivity and high oil-flooding capacity, CO₂ flooding has become a very potential method to improve oil recovery in low permeability / tight oil reservoir, but influenced by reservoir heterogeneity and fractures, gas channeling easily happens during the injection affecting the development of reservoirs. The joint CO₂ flooding and huff-n-puff experiments were designed and conducted in core with different permeability contrast, and oil recovery and oil distribution (scanned by CT) was measured as the index to investigate the effect of heterogeneity on CO₂ flooding. The results show that, during the continuous injection of CO₂, as the permeability contrast increases from 1.0 to 2.2, the oil recovery is significantly reduced from 88.5% to 58.3%; when this contrast further increase from 2.2 to 154.0, the decreasing trend of oil recovery slows down from 58.3% to 44.8%. The distribution of residual oil shows that the injected CO₂ mainly flows in

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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: (1076) HTML (0) PDF (1.44 MKB)(4132)

  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.

• 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: (1870) HTML (0) PDF (1.15 MKB)(3389)

  Abstract:

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

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

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

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

  Abstract: (1037) HTML (0) PDF (1.32 MKB)(3259)

  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: (1311) HTML (0) PDF (1.20 MKB)(3197)

  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

• 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: (1505) HTML (0) PDF (1.23 MKB)(3054)

  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.

• 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: (1240) HTML (0) PDF (2.17 MKB)(2952)

  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.

• 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: (1402) HTML (0) PDF (2.35 MKB)(2870)

  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.

• 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: (612) HTML (0) PDF (1.18 MKB)(2658)

  Abstract:

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

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

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

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

  Abstract: (345) HTML (0) PDF (1.25 MKB)(2645)

  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 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: (1728) HTML (0) PDF (2.12 MKB)(2553)

  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.

• 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: (995) HTML (0) PDF (1.02 MKB)(2520)

  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.

• 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: (1267) HTML (0) PDF (2.10 MKB)(2282)

  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.

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

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

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

  Abstract: (1213) HTML (0) PDF (1.65 MKB)(2162)

  Abstract:

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

• 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: (1105) HTML (0) PDF (1.38 MKB)(2158)

  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.

• Advance of Fractured Formation Lost Circulation Mechanism and Lost Circulation Materials in Oil and Gas wells

  ZHAO Hongbo1，2，3，SHAN Wenjun2，3，ZHU Disi2，3，YUE Weimin2，3，HE Yuanxin1，2，3

  2021,38(4):740-746, DOI: 10.19346/j.cnki.1000-4092.2021.04.028

  Abstract: (565) HTML (0) PDF (1.19 MKB)(2121)

  Abstract:

  The latest achievements in the aspects of lost circulation mechanism，types of lost circulation materials，drilling fluid formulation and technology was reviewed. In addition，the engineering methods of well prevention，such as well strengthening， and the advantages and disadvantages of the methods for determining the leakage layer was also introduced. Finally，some suggestions was given，which can be used for reference in the future.

• 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: (1087) HTML (0) PDF (1.22 MKB)(2105)

  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.

• 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: (975) HTML (0) PDF (1.28 MKB)(2086)

  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.

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

  HU Ting

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

  Abstract: (871) HTML (0) PDF (1.22 MKB)(2080)

  Abstract:

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

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

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

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

  Abstract: (916) HTML (0) PDF (1.33 MKB)(2059)

  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.

• Development and Application of an Environment-friendly and Non-fluorescent Biomass Lubricant

  ZHANG Xiaogang，SHAN Haixia，LI Bin，ZHANG Yi，ZHOU Yaxian，WANG Zhonghua

  2019,36(2):196-200, DOI: 10.19346/j.cnki.1000-4092.2019.02.002

  Abstract: (1367) HTML (0) PDF (1.29 MKB)(2052)

  Abstract:

  A new fluorescent-free biomass lubricant ZYRH was developed to overcome the disadvantages of high fluorescence level and poor thermal stability of commonly used lubricants. The fluorescence grade，emulsifying stability，lubricity，temperature resistance and salt resistance of ZYRH were studied. The effects of ZYRH on the rheology and wall building properties of drilling fluid were investigated. The results showed that the ZYRH level was less than 3，the stability of emulsification was good，the tolerance to temperature was up to 200℃，and the salt resistance was saturated. After adding 1% ZYRH lubricant to the base pulp， the decrease rate of the extreme pressure lubrication coefficient was 91.5%—93%，the biological toxicity EC50>1×10⁶ mg/L. ZYRH was compatible with polymer drilling fluid，polysulfonate drilling fluid and microbubble drilling fluid. ZYRH was applied in 25 wells，such as Wei 455 well and Wen 23 gas storage，and achieved good results，and the product had no pollution to the environment.