Abstract:In view of the problems of poor safety，leakage and large reservoir pollution in the process of workover of sour gas fields containing H₂S，CO₂，SO₂ and other acid gases in Sichuan and Chongqing area，a liquid gel plug system suitable for high-acid gas wells was obtained by optimizing vegetable gum thickener，adjusting pH value，adding antacid inhibitor. The rheological properties of the system，as well as the pressure bearing capacity，temperature stability，hydrogen sulfide resistance，and gel breaking performance after gel formation were investigated，and the field application in high-acid gas wells was carried out. The gelling time of the system，composed of 3% thickener，3% thickening dispersant，7% cross-linking agent，5% conditioner，1% acid inhibitor and regulator，was adjustable from 28 min to 200 min. The viscosity after gelling was greater than 30 Pa·s，indicating that the strength of the system was high. The gel did not break after aging for 24 h at the temperature of 150 ℃，and the gel did not break when soaked in the acid gas layer water containing 300 mg/L H₂S or 100 mg/L CO₂ for 72 h. The pressure bearing capacity was the best when the pH value of the system was 8. When adding the blockage relieving fluid，the liquid gel plug could be broken within 1—6 hours at the temperature of 50—80 ℃，and the viscosity of the broken fluid was lower than 3 mPa·s. The liquid gel plug system had been successfully applied in wells with H₂S content of 80 mg/L，which provided the technical support and guarantee for the well repair in Sichuan and Chongqing acid gas field.

Abstract:In order to solve the problem of poor salt tolerance of polymer emulsion thickening agent for fracturing and the poor stability of suspension thickener，based on the salt resistant associating polymer KFPY，the stabilizer，the particle size and proportion of the powder polymer thickener were optimized by determining the stability time and the bulk viscosity of suspension slurry thickener，the suspension emulsion thickening agent GAF-TE formula was formed as follows：48.5% white oil，1.5% emulsifying agent G10，5% organic modified bentonite and 45% salt resistant associating thickener KFPY. The performances of the GAF-TE including solubility，viscosity increasing，drag reducing and proppant transporting were evaluated in the formation water of Ma 18 well. The results showed that the dissolution time of 0.1% GAF-TE was 18 s，the viscosity was 2.19 mPa·s，and the drug reduction rate was 76.8% . The dynamic carrying capacity of the GAF-TE slickwater was better than that of the ordinary polyacrylamide emulsion. The surface tension of the GAF-TE slickwater was 26.8 mN/m，and the interfacial tension between the GAF-TE slickwater and the kerosene was 0.96 mN/m. The lower damage rate of the GAF-TE slickwater to core permeability was 6.97% . The GAF-TE had been applied in Xinjiang oilfield and showed good solubility，drug reduction and sand carrying performance.

Abstract:In order to improve the problem of high friction resistance at the front end and low viscosity at the tail end of fracturing fluid in shale reservoir fracture network volume fracturing，the steric hindrance of twin tail monomers with different carbon chain lengths，mean square terminal distance and mean square displacement of polymer materials were simulated based on molecular dynamics. The drag reducer LMA-DiC¹²AM-AM（LAD）was synthesized by micellar polymerization with lauryl methlacrylate （LMA），acrylamide（AM）and N，N-dodecyl acrylmaide（DiC¹²AM），then the structure was characterized. The rheological property，drag reduction and sand-carrying capacity of LAD solution were studied by rheometer and friction tester. The results showed that DiC¹²AM monomer had 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 had good shear stability（viscosity＞75 mPa·s），shear recovery performance and sand-carrying capacity. The temperature-resistance capacity was up to 60 ℃ ，meanwhile the drag reduction rate reached 67.4%. LAD had both drag reduction and sand-carrying properties，which was basically consistent with the simulation result.

Abstract:Aiming at the problem of high density and no water control effect of conventional ceramsite proppants，the surface of the ultra-low-density organic proppant（ULDOP）matrix was oxidized at a high temperature to generate active groups on the surface，and then the nuleophilic addition reaction of the activated ULDOP and perfluorocarboxylic acid was carried out to obtained an ultra-low-density water-controlling proppant（ULDWCP）. The wettability，water resistance and oil-water phase percolation properties of the ULDWCP were evaluated，and the field application tests were carried out. The results showed that the contact angle of water on the surface of the ULDWCP reached up to 158.6°，and the water blocking height was 25 cm. Compared with before modification，the seepage flow resistance of the formation water increased by 40% ，indicating obvious selective water controlling effect，and the erosion resistance of ULDWCP was excellent. The filling rate of the ULDWCP in field test had reached up to 100%，and the water cut and the rising rate of water cut after production were far lower than those of adjacent wells，and the oil production was significantly higher than that of adjacent wells，showing a good application prospect.

Abstract:The casing damage of gas well in Changqing oilfield is serious，and there are some problems such as poor gas tightness and difficult injection during the cement sealing process. In order to improve the air tightness and strength of epoxy resin after curing for casing damage repair，the composite resin was prepared using nano-SiO₂ doped epoxy resin for repairing gas well damage. The properties of the composite system were evaluated by rheological properties before curing，mechanical strength and plugging ability after curing，and the curing mechanism of the composite system was studied by scanning electron microscope. The results showed that the nano-SiO₂/epoxy resin composite system had the characteristics of shear dilution and viscoelasticity，and the curing time of the composite system was more than 3 h at different temperatures，providing sufficient injection time. Compared with conventional resin，the compressive strength and tensile strength of the cured nano-SiO₂/epoxy resin could reach 106.8 MPa and 72.1 MPa，and the plugging strength of pore could reach up to 37.7 MPa，which could effectively prevent formation fluid from entering the wellbore. Nano-SiO₂ could repair the micro-cracks of the cured resin，and thus improve the mechanical strength. Changqing oilfield gas well construction showed that the composite system had strong sealing and bearing capacity，which provided support for casing damaged well repair and re-fracturing wellbore reconstruction.

Abstract:In order to make oleic acid evenly distributed in cement and prepare the hydrophilic cement material，the carrier quartz sand was modified by the hydrophobic material oleic acid，and OA-1 cement was obtained by introducing the modified quartz sand， and the overall wettability and compressive strength of cement test block was tested. At the same time，it was compared with OA-2 and OA-3 cement prepared by the direct addition of oleic acid and the dissolution of oleic acid with isopropanol，respectively. The microstructure and chemical composition of hydrophobic cement materials were characterized by SEM and XRD. The results showed that the average value of the contact angle of water on the OA-1 cement with oleic acid content of 5% could reach up to 145.18 °，indicating that the OA-1 cement had best hydrophobic effect. The compressive strength of the OA-I cement after curing for 3 days was greater than 21 MPa. Compared with that of blank cement，the water permeability of the OA-1 cement increased obviously，the average change rate was 77.87%，while the oil permeability of the OA-1 cement decreased obviously，the average change rate was 32.14%. OA-1 cement had selective water plugging effect and could achieve the purpose of oil stabilization and water control. Using quartz sand as a carrier，the oleic acid was wrapped in the surface of quartz sand without solvents，a uniform distribution of oleic acid could be achieved in the cement，thereby obtaining hydrophobic well cement.

Abstract:In order to solve the problems of complicated preparation processes of common profile-controlling and flooding agents and the addition of organic solvents，the micro/nano-polyacrylamide gel dispersions for profile-controlling and flooding were prepared based on reversible addition fragmentation chain transfer（RAFT）aqueous polymerization. First，water-soluble RAFT agent was synthesized using 2-mercaptopropionic acid，carbon disulfide and α-bromophenylacetic acid as raw materials. Then， the polyacrylamide gel dispersions were prepared in pure water by one-step method with RAFT agent，acrylamide，crosslinker N，N'-methylenebisacrylamide bis-acrylamide and initiator （NH₄）₂S₂O₈. The morphology and size of gel dispersions were characterized. The effects of reactant ratio，polymerization temperature，polymerization time and solid content on the properties of gel dispersions were investigated. The rheological and viscoelastic properties，temperature，salinity and pH responsiveness of gel dispersions were studied. The results showed that the gel dispersions had irregular globular structure and the molecular scale was micro/nano scale. The micron diameter of gel dispersions was 0.92—6.13 μm and the diameter of nanoparticles was 48—87 nm. The characteristic of polyacrylamide gel dispersions was close to the Newton fluid，and its viscoelasticity exhibited the characteristic of viscous fluid，which further confirmed that gel dispersions were formed by small gel unit particles dispersing in aqueous solution. The viscosity of gel dispersions decreased with the increase of temperature and pH value，but the degree of reduction was small， and their viscosity was almost not affected by mineralization. Compared with traditional preparation technology of profile-controlling and flooding agents，the method of preparing gel dispersions in pure water had the characteristics of short time， simplified preparation condition，without organic solvent and small molecular scale of product.

Abstract:Deep fluid diversion technology is an urgent problem to be solved in Bohai oilfield. In this paper，the performance of three kinds of polymer microspheres was evaluated by biomicroscopy technology and core displacement experiment. Furthermore， the field test of microsphere was carried out in Bohai B oilfield. The results showed that under the environment of Bohai reservoir， such as 65 ℃ temperature and 8.9 g/L salinity，compared with SMG and COSL microsphere，the size of NWKY microsphere whose main component was crosslinked polymer with acrylamide-2-methylpropanesulfonic acid and hydrophobic monomer increased from 1.98 μm to 18.14 μm after expanding slowly for 7 days in simulated water. The expansion multiple was the largest， indicating good hydration expansion effect. The particle size and expansion multiple were close in high salinity water and low salinity water，showing good salt resistance. Under the condition of 95 ℃，NWKY microsphere still had good slow expansion effect，indicating good temperature resistance. The adaptive reservoir permeability of NWKY microsphere was 200×10^-3 —1500×10^-3 μm²，which could meet the needs of oilfield. The implementation of NWKY microsphere in Bohai B oilfield achieved good results. The incremental oil of expected was 7432 m³.

Abstract:Polymer flooding widely used in oilfields for a long time. As a result，there are serious plugging of oil wells and the liquid volume decreased，which seriously affects the further development of reservoirs after polymer flooding. For polymer flooding reservoirs in Shengli oilfield，X-ray diffractometer，scanning electron microscope and other technical means were used to analyze the composition of oil well plugging products. By simulating different plugging fluids and near-well reservoir conditions，the plugging degree and main controlling factors of oil well plugging were studied. The results showed that the plugs in the oil wells of polymer flooding reservoirs were mainly polymer aggregates（65.6%）that were cross-linked and embedded to adsorb formation mineral salts and clays，followed by formation sand particles and cements（17.8%），and crude oil（16.6%）. The plugging of porous media that caused by the formation of sand particles was the main controlling factor of plugging near the oil well. The polymer agglomerates that formed by polymer derivative cross-linking and adsorption agglomeration aggravated the degree of blockage of oil well. Based on the guidance of the research on plugging mechanism of polymer flooding reservoirs，the integrated prevention and control program of oil well plugging and sand control，which was composed of crude oil cleaning and oxidative degradation of polymer micelles in near well，and effective sand consolidation control in far well，had good application effects. The average single well extraction was 86.8%.

Abstract:During the production of Gaotan-1 well in Junggar Basin，a large amount of black solid-like sediments were formed on the inner wall of oil tubing，which seriously affected the production. Aiming at this problem，trichloroethylene was used to extract organic and inorganic substances from different parts of the sediment in wellbore. The composition of organic and inorganic substances was characterized. At the same time，the influence of inorganic substance on the adsorption and deposition of crude oil was analyzed，then the formation mechanism of sediment was further explored. The results showed that the content of organic and inorganic components was quite different. The inorganic content in the center of the sediment reached 71.51%，but that was only 16.55% in the darker part of the surface. However，the content of organic compounds in different parts was similar，with asphaltene accounting for 52.71%—58.37%. The asphalt molecular connected with large side chain length and a high degree of branching was more likely to be deposited. The inorganic substance in the sediment was mainly barium sulfate. Its lamellar structure with rough surface intensified the adsorption of asphaltene. The deposition mechanism of asphalt scale in Gaotan-1 well was that inorganic particle such as lamellar barium sulfate with 1—20 μm adsorbed the association of asphalt molecule with long side chain and high branching degree in crude oil，then the large particle accumulation with 20—100 μm was aggregated，which together formed deposit and adhered to the wellbore，resulting in the blockage of pipe string.

Abstract:Due to small pores，smaller throat，and lower mobility of crude oil in Jilin low permeability tight reservoir，water drive effect is poor. A nano fluid enhanced permeability and oil displacement（NFEPOD）system was adopted，and through the core oil displacement experiment the oil displacement efficiency of the NFEPOD system on the tight core was investigated，through the core nuclear magnetic resonance test and CT scanning，the influence of the pore structure of the tight reservoir on the oil displacement effect of nano fluid was focused on. The results showed that the NFEPOD system could reduce the injection pressure of tight core oil displacement experiment，with a maximum decrease of 46.2%. When the pore structure of tight reservoir was good，the oil displacement effect was obvious，with a maximum increase of 30.21%. The NFEPOD system could remarkably enhanced oil recovery when the crude oil was distributed in pore throat with an average pore radius greater than 1 μm. CT scanning of cores showed that the average pore throat radius，effective connected pore ratio and pore coordination number of tight cores would affect the injection pressure and oil displacement efficiency of the NFEPOD system，the average pore throat radius and the proportion of effectively connected pores had a greater impact.

Abstract:In order to reveal the mechanism that carbon dioxide dissolved in heavy oil in the presence of solubilizer，the solubility of carbon dioxide in heavy oil was experimentally determined as a function of temperature，pressure and the content of solubilizer 1，2-dimethoxyethane. The solubility parameters of carbon dioxide under different conditions were calculated by molecular dynamics simulations. The radical distribution functions of carbon dioxide and solubilizer were calculated. It was found that lower temperature，higher pressure and greater content of solubilizer are favorite to the dissolution of carbon dioxide，in accordance with that found in experiments. It is the strong attraction between carbon dioxide and 1，2-dimethoxyethane molecules that led to the solubilization of carbon dioxide in heavy oil. The results provide a theoretical direction to development of solubilizers of carbon dioxide in heavy oil. Those small organic molecules rich in ether groups are potential solubilizers of carbon dioxide.

Abstract:Montmorillonite is an important clay mineral in sedimentary rocks. In order to explore the impact of CO₂ injection on montmorillonite and clarify the chemical behavior of montmorillonite in CO₂ aqueous solution，the state of montmorillonite reacting with CO₂ for 7 days and 30 days at 10 MPa and 60 ℃ was systematically evaluated by means of XRD，XRF and ICP，The changes of solid elements，crystal structure and ion concentration in reaction solution before and after montmorillonite powder reaction were compared. Combined with the structural characteristics of the original montmorillonite，the change mechanism of montmorillonite in acid was clarified. The results showed that the concentrations of Ca²⁺，Mg²⁺and Al³⁺ in the liquid phase first increased and then decreased after the reaction of montmorillonite with CO₂. The concentration of Si⁴⁺ increased first and then tended to be stable. The crystal surface corresponding to d（001）in the solid phase was destroyed after the dissolution reaction. Compared with Al³⁺ and Si⁴⁺， the variation range of Mg²⁺，Ca²⁺ and Na+ in the reaction process was relatively large. On the one hand，due to the large cation exchange capacity of montmorillonite，the active cations with large radius such as interlayer Na⁺ ，Mg²⁺ ，Ca²⁺ were easy to be replaced by H+ with small radius；on the other hand，the interlayer intermolecular force of montmorillonite was van der Waals force，which was weak relative to electrostatic force，and the structure was easy to be damaged. Under acidic conditions，the stability of silica tetrahedron was slightly stronger than that of alumina octahedron，but amorphous Si in montmorillonite was easy to dissolve，which made the change range of Si greater than that of Al.

Abstract:There are some problems in water drive development of low permeability reservoirs，such as insufficient formation energy and difficult water injection. On the one hand，the water injection pressure is high and the under injection is serious. On the other hand，the formation pressure drop is large，the production capacity decreases rapidly. The oil production rate and recovery degree are low. There are still various forms of residual oil such as film or oil drop after water flooding. Aiming at such problems， the asymmetric Gemini surfactant was prepared from epichlorohydrin，dodecyl dimethyl amine and metronidazole. It was compounded with dehydrogenated rosin surfactant，cetyl alcohol and ethanol to obtain a functional injection increasing oil displacement agent. The emulsifying ability，wettability，anti-swelling，depressurization，injection increase and oil displacement effect of the agent were studied. Then it was applied on Bonan oilfield. The results showed that the functional injection increasing displacement agent could not only adsorb on the oil-water interface and reduce the oil-water interfacial tension，but also emulsify crude oil and remove the oil film. The cationic component took water as the transfer medium to form a molecular film on rock surface，which could stabilize clay，improve the wettability of rock surface，reduce injection pressure and improve water injection recovery. The functional injection increasing displacement agent had good anti swelling effect，depressurization，injection increasing and oil displacement effect when its concentration was low. In the field test of pressure flooding，the injection capacity of water injection wells and the oil production capacity of corresponding oil wells were significantly improved.

Abstract:The emulsifying ability of surfactant has a great impact on improving the oil displacement effect after water flooding development of low-permeability reservoir. In order to enhance the emulsifying performance of surfactant oil displacement system and improve oil displacement efficiency，anion non Gemini surfactant GEY-2 with good interfacial activity and non-ionic surfactant 6501 with strong emulsifying ability were combined，a strong emulsion composite surfactant flooding system suitable for low permeability reservoir was developed，and its comprehensive performance was evaluated. The results showed that the strong emulsifying composite surfactant oil displacement system had good temperature resistance and salt resistance. Under the conditions of high temperature and high salinity，the oil displacement system composed of 2000 mg/L GEY-2 and 3000 mg/L 6501 could still maintain urtralow oil-water interfacial tension，being of 10^-3 mN/m. The emulsified water rate of the elusions，which was formed through combing the composite surfactant oil displacement system with the crude oil in volume ratio of 7∶3，was 90.2% and 61.2% after placed at the temperature of75 ℃ for 10 min and 100 min，respectively，which indicating the system had strong emulsifying property. The system had good anti-adsorption performance，which could reduce the waste of oil displacement agent and effectively ensure the oil displacement effect. The composite surfactant flooding system had a good oil displacement effect on low-permeability cores. When the core permeability was 11.38×10^-3 μm²，the oil recovery could be enhenced by more than 20% by injecting 0.5 PV strong emulsion composite surfactant flooding system after water flooding. The field application results showed that after the implementation of strong emulsion composite surfactant displacement measures in the low permeability block of H oilfield，the injection well pressure increased，the daily oil production of corresponding oil wells increased from 2.20 t to 5.41 t，and the average water cut decreased from 89.2% to 71.5%，which achieved a good oil increase effect.

Abstract:In view of the poor development of high-pour-point oil by cold water injection，a high-efficiency surfactant that can form microemulsion with crude oil was used，and the adaptability of the surfactant for enhancing high-pour-point oil recovery was determined through analyzing the surfactant-oil interaction and high-pour-point oil displacements effect by single surfactant，the corresponding combination and foam systems. The results showed that the surfactant IMS with mass fraction of 0.1% could effectively reduce the oil-water interfacial tension to 0.6×10^-3 mN/m. The obtained microemulsion could dissolve preferentially the light component of oil，which could not significantly reduce the wax-evolution point and freezing point of the high-pour-point oil. The oil recovery by surfactant huff-n-puff and displacing injection with concentrations of 0.1%—2.0% and utilizations of 0.25—0.5 PV was 1.7%—12.3%，and additional soaking operation could not further improve such oil recovery. The presence of polymer or foam in surfactant solutions could obviously enhance the oil displacement，and the oil recovery by the corresponding binary combination flooding system of 1.0% surfactant+0.2% polymer with the injection volume of 0.5 PV was 18.4%，while those of the surfactant foams with different surfactant concentrations of 1.0% and 0.3% when gas liquid ratio was 2∶1 and the surfactant solution volume was 0.5 PV，were 17.3% and 16.8%，respectively. However，the binary combination flooding behaved a high injection pressure and had underlying injection problem in the low permeability reservoirs，while the foam system performed a relatively low injection pressure and could enhance oil recovery effectively.

Abstract:In order to improve the temperature resistance and salt resistance of polyacrylamide oil displacement agent，the molecular structure design idea was adopted to design the polymer structure from the primary and secondary structures of the polymer，and the advanced structure and molecular chain aggregation state of the polymer were analyzed and integrated. Taking AM and AMPS as the main monomers，a random micro-branched/micro-crosslinking associating polymer was synthesized by introducing self-made hydrophobic monomer and branched monomer. The effects of AM/AMPS ratio，branched monomer dosage， hydrophobic monomer dosage，pH value and initiation temperature on the viscosity of the polymer were studied by orthogonal test， and the temperature resistance and salt resistance of the polymer were studied. The results showed that the order of the influence of various factors on polymer viscosity was as follows：branched monomer dosage ＞ hydrophobic monomer dosage ＞ AM/AMPS molar ratio ＞ pH value ＞ initiation temperature. When the molar ratio of AM to AMPS was 5∶1，the amount of branched monomer was 0.5‰，the amount of hydrophobic monomer was 1‰，pH value of the system was 7，and the initiation temperature was 2 ℃，the obtained polymer had the highest viscosity. The synthesized random micro-branched/micro-crosslinking associative polymer had high intrinsic viscosity of 2 868 mL/g，lower insoluble content of 0.12%，higher polymer viscosity and better thermal stability. The viscosity of the polymer solution with the concentration of 1 500 mg/L was 12.8 mPa·s after aging for 180 d at high temperature of 95 ℃ and at salinity of 40 000 mg/L，and the viscosity retention rate could reach more than 85%. After aging，the random micro-branched/micro-crosslinked association polymer solution could still meet the viscosity requirements of oil displacement agents，and the polymer solution had excellent long-term stability in the formation.

Abstract:According to the nutrient requirement of the main oil recovery functional bacteria in the sandstone reservoir of Lu 9 well block，by-products of fermentation and agricultural wastes were selected as the main component of the nutrient medium，which also contained some auxiliary microbial growth factors. The optimum carbon source，nitrogen source and phosphorus source were selected through single factor experiment. 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，then the concentration of each component was determined. Finally，response surface test was used to further improve the concentration of each component. Moreover，oil displacement experiment was performed under simulated reservoir condition. The results showed that the nutrient system was efficient and cheap. The nutrient medium contained 0.15% by-products of fermentation and agriculture， 0.6% mineral salt with nitrogen content of 16.47%，and 0.25% mineral salt with nitrogen content of 26.16%. The oil emulsifying effect of the system was good. The copy number of hydrocarbon oxidation gene，which could activate the main oil recovery function gene，reached 10⁷ copies/mL. In the physical simulation oil displacement experiment，the recovery factor could increase 11.65 percentage points after injecting 0.4 PV nutrient system and air at a gas-liquid volume ratio of 8∶1. Compared with the formula used in the field，the optimum formula could reduce the cost by 20.25%. The screening and evaluation process of activation system could provide reference for the screening and evaluation of nutritional system.

Abstract:There are some problems of high temperature，high viscosity，high water cut and low water flooding efficiency in Luo 9 Shi 1 block. In order to improve the output of high water-cut oil well，the composite system of microbial polysaccharide and microbial fermentation broth was developed. Its temperature resistance，plugging performance，emulsion viscosity reduction and oil displacement efficiency were studied. Finally，the composite system was applied on this block. The results showed that the viscosity of new microbial polysaccharide remained in the range of 120—125 mPa·s all the time from 55 ℃ to 95 ℃，indicating strong temperature resistance. When the new microbial polysaccharide was injected into the core，the pressure increased while the permeability decreased by 53.3%. It could effectively seal the core. The microbial fermentation broth was composed of fermentation broth I mainly contained rhamnolipid biosurfactant and fermentation broth II mainly contained sugar-protein-lipid biological emulsifier. When the volume ratio of Ⅰ to Ⅱ was 1∶2，the emulsification ability at high temperature of microbial fermentation broth was the strongest. The rate of emulsification viscosity reduction to oil was 81.4%. The physical simulation of oil displacement experiment showed that the composite system of microbial polysaccharide and microbial fermentation broth had improved oil recovery by 13.9 percentage points，which was better than that of single system. The application results of single well huff-and-puff showed that four oil wells had the significant effect of increasing oil and dewatering with the cumulative oil increase of 2730 t. It effectively improved the low efficiency of oil well in Luo 9 Shi 1 block.

Abstract:In order to develop a new type of slick water reducer，the long-chain end-group hydrophobic associating polymer HPAM-L was prepared from acrylamide（AM），hydrophobic monomer dodecyldimethylallylammonium chloride（C₁₂DMAAC）， sodium acrylate （NaAA） and homemade long-chain hydrophobic initiator 2，2'-azobis（isobutyl）dodecamidine hydrochloride （AIBL）. The structure and properties of HPAM-L were characterized by infrared spectroscopy，nuclear magnetic resonance spectroscopy， Ubbelohde viscometer， fluorescence spectrophotometer and rotational rheometer. The resistance reduction performance of HPAM-L solutions with different concentrations was measured by using fracturing fluid friction tester. The results showed that the relative molecular weight of HPAM-L was 7.43 × 10⁶，and the critical association concentration was 1—1.5 g/L. HPAM-L had good temperature resistance and shear stability. The aqueous solution of HPAM-L had a wide linear viscoelastic region. The higher the concentration，the more obvious the elastic characteristic was. The maximum drag reduction rates at the solution mass fractions of 0.075%，0.086%，0.1% and 0.15% could reach 71.6%，73.1%，73.3% and 74.1%，respectively， showing good drag reduction performance.

Abstract:In order to meet the demand for demulsification and cost of oilfield chemicals in Xinjiang oilfields and reduce the environmental pollution，this article based on the environmental safety and the complex situation of shale oil fracturing produced fluids in Madong block of Xinjiang. Ten kinds of biodemulsifiers synthesized by microbial fermentation were screened and the evaluated by the bottle test method. The demulsification of the fermentation broth and the purified extract was compared. Meantime，the compound demulsification effect of biological demulsifier and conventional chemical demulsifier was studied，and then the process of demulsification was optimized. The results showed that the biodemulsifier XJ-4-2 synthesized by XJ-4 bacteria had good compatibility with the extracted fluid from Madong block. The dehydration rate was more than 80%. Under the condition of 60 ℃ and 120 min demulsification time，the dehydration rate of the compound system containing biological demulsifier XJ-4-2 and chemical polyether demulsifier reached near 95%. Under the condition of 50 ℃，200 mg/L dosage and 2 h thermochemical sedimentation，the water content of remaining crude oil and oil content of sewage were decreased. The biological demulsifier had high dehydration rate and low oil content in sewage at low temperature，which improved the problem of rapid low-temperature dehydration of shale oil fracturing produced fluids in Madong block.

Abstract:Tight oil has high cost of demulsification due to its strong emulsifying stability. Taking Jimusar tight oil as the research object，the effects of different resin content and oxidation degree on the interface stability of produced liquid were explored by analyzing the composition of tight oil. The results showed that the content of resin in Jimusar tight oil was 16.83%，while that of asphaltene was only 0.3% . The high content of resin might be one main reason for the stability of tight oil emulsion. After the oxidation of resin，the oxygen content in resin increased for the production of partial carboxyl substances，which increased the interface activity of the resin and thus was not conducive to demulsification. When the oxidation of resin was regulated by 0.4%H₂ O₂ solution，the aromaticity increased while the polarity decreased. As a result，the contact angle between tight oil and water decreased，while the interfacial tension increased. Furthermore，the storage modulus and loss modulus of tight oil emulsion and the interfacial membrane strength decreased，which was beneficial to the demulsification. At the temperature of 80 ℃ ，the demulsification rate of tight oil emulsion was increased from 65.0% to 82.2% by using demulsifier after the oxidation pretreatment 30 min with 0.4% H₂ O₂ solution，which provided theoretical support for the efficient demulsification of produced liquid in tight oil on site.

Abstract:Deep silicon removal of super-heavy oil produced water was developed through electrocoagulation by using aluminum plates as cathode and anode. The influence factor of electrocoagulation was optimized. Then the optimum pH value，current density，polyaluminum chloride（PAC）and anionic polyacrylamide（PAM）dosage were obtained. The results showed that single electrocoagulation could not achieve deep silicon removal. Electrocoagulation together with PAC and PAM had a synergistic effect on the removal of silicon from super-heavy oil produced water. Under the condition of 200 mg/L PAC，8.0 pH value，10 mA/cm² current density and 50 mg/L PAM，the removal rate of SiO₂ increased with increasing electrocoagulation time，but the increment decreased. When the electrocoagulation time was 13 min，the SiO₂ content in electrocoagulation effluent was 20 mg/L，meanwhile the SiO₂ removal rate was 92%，which achieved deep silicon removal.

Abstract:The amide groups in the polymer （partially hydrolyzed Polyacrylamide and its derivatives） used in chemical combination flooding are liable to be hydrolyzed and their properties changed，resulting in reducing the effect of chemical flooding. A rapid high-performance liquid chromatography method for the determination of the degree of hydrolysis of polymers in trace samples of chemical flooding systems was described. It was used to study the variations of polymer hydrolysis degree in chemical flooding system under different conditions. Experimental results showed that methods could be applied for determination of hydrolysis of polymers in trace sample of chemical flooding，hydrolysis of polymers in the environment of reservoir was affected by connate water，alkali type of chemical combination flooding system，temperature and other factors. The degree of hydrolysis of the polymer prepared with distilled water at 34 ℃ could be obviously detected，oilfield water of NaHCO₃ water-type could promote the hydrolysis of polymers. The rate of hydrolysis reaction in chemical flooding system was in turn：strong base（NaOH）systems ＞weak base（Na₂CO₃）systems ＞ base free systems. The degree of hydrolysis of polymers in various systems increased continuously during the 90 days of experiment when the temperature was above 60 ℃，the degree of hydrolysis of polymers in strong base system was close to 60% after aged for 90 days.

Abstract:In order to study the stability of emulsions with different water cut，the self-emulsification of crude oil and produced water with different water cut was analyzed，and combined with nuclear magnetic resonance（NMR），the stability characteristics of emulsions with different water cut in Bohai Sea A reservoir was identified. The results show that under the conditions of 65 ℃（formation temperature）and 3000 r/min rotation speed，the crude oil and water are completely emulsified at water cut of 40% and 50%，and water-in-oil emulsion（W/O）was formed，the average particle size of the emulsion was 1.905 μm and 1.487 μm，and the interfacial tension was 23.93 mN/m and 18.89 mN/m，respectively. The relaxation time and self-diffusion coefficient of the emulsion with 40% and 50% water content were the smallest，the relaxation time and self-diffusion coefficient of the emulsion with 60% water content was the second，while the relaxation time and self-diffusion coefficient of emulsion with 70% water content were the largest. When the moisture content was 40%—50%，the emulsion was the most stable. Combined with NMR technology， the smaller the average particle size of the emulsion，the higher the emulsion viscosity，the lower the interfacial tension，the smaller the relaxation time and self-diffusion coefficient，the better the emulsification effect.

Abstract:The detection method of scale inhibitor concentration in the produced fluid of ASP flooding oil well is still blank. In the paper，the determination method of inductively coupled plasma emission （ICP） was studied，and the effects of polymer， surfactant，alkali and silicon ions in ASP produced fluid on the determination of scale inhibitor concentration were analyzed. The results showed that polymer had the greatest influence on the concentration detection of scale inhibitor，surfactant，alkali and silicon ions had little influence on the concentration detection of scale inhibitor，and the highest average accuracy deviation was only 2.6%. In order to eliminate the influence of polymer，oxidative degradation pretreatment was used，as a result，the average accuracy deviation was reduced from 38.9% to 0.2%.The field test of scale inhibitor concentration detection was carried out in 30 oil wells in a ASP flooding test block of Daqing oilfield by ICP method. The coincidence rate of reagent scheme was increased from 80% before detection to 96%，and the pump-testing period was increased from 210 days to 270 days.

Abstract:With the continuous development of oil/gas drilling to the deep，the temperature of deep and ultra-deep formations drilled are getting higher and higher，which puts forward more requirements for drilling technology，especially technology of drilling fluid. In combination with the actual requirements of ultra-high temperature drilling，the technical barriers of water-based drilling fluid under ultra-high temperature and the effect of ultra-high temperature on water-based drilling fluid performance were analyzed. Research progress of key additives for water-based drilling fluid under ultra-high temperature and water-based drilling fluid system they constructed was described，and the future development direction of water-based drilling fluid under ultra-high temperature was discussed.

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.

Abstract:Low salinity water flooding means injecting water with salinity of 1—5 g/L into the formation to enhance oil recovery. The mechanism of low salinity water flooding to enhance oil recovery is still controversial. By sorting out the development history of low salinity water flooding technology，the main mechanism of enhanced oil recovery by low salinity water flooding in sandstone reservoir could be roughly divided into two aspects，such as particle migration and wettability change. The mechanism of enhanced oil recovery by low salinity water flooding in carbonate reservoir was briefly described，including the change of double electric layer and ion reaction caused by mineral dissolution. The reservoir condition suitable for low salinity water flooding technology was analyzed. Then the new technology combining low salinity water flooding with other oil flooding technology was summarized. The application of molecular simulation technology in low salinity water flooding was introduced. Finally，some suggestions for future development were put forward.

Abstract:Scaling has a serious impact on oil production. Adding scale inhibitor is one of the most effective methods to inhibit scaling at present. The problems faced by the application of traditional scale inhibitors in oil fields，such as environmental pollution and poor high temperature resistance，was introduced. The research status of green scale inhibitors was summarized，focusing on green scale inhibitors such as polyepoxysuccinic acid and polyaspartic acid. the methods and scale inhibition mechanism of enhancing the performance of scale inhibitors were expounded from the direction of introducing modified groups such as carboxyl， amino and amide groups. Finally，the development direction of green scale inhibitor was prospected，which had reference value for the future development of this field.