Abstract:In order to improve the temperature resistance of emulsifier for oil-based drilling fluid，main emulsifier（PF-EMUL HT） and auxiliary emulsifier（PF-COAT HT）were prepared by using vegetable oleic acid，diethylenetriamine and maleic anhydride. The molecular structure and temperature resistance of two emulsifiers were characterized by infrared spectrometry and thermogravimetric analysis. The emulsifying ability and temperature resistance of two emulsifiers were analyzed by measuring the dynamic interfacial tension，emulsification efficiency and electrical stability of the emulsion. The possible emulsification mechanism was also proposed. At the same time，the influences of emulsifier dosage，oil-water ratio，temperature and density on the performance of drilling fluid were studied. The results showed that PF-EMUL HT had amidation group，while PF-COAT HT had multi-functional groups，such as amido group and carboxyl group. These two emulsifiers could effectively reduce the interfacial tension between oil and water. The demulsification voltage of the emulsion prepared by the two emulsifiers was more than 370 V. The emulsification efficiency was 96% after aged at 232 ℃. The oil-based drilling fluid had favorable stability after aged under the conditions of 150—232 ℃ and 60:40—90:10 oil-water ratio，which could satisfy the operation needs of high temperature and high pressure well and directional well.

Abstract:Graphene oxide（GO）can realize film-forming covering and plugging of nano-micro pores in shale. In order to improve its temperature resistance，carboxylated graphene oxide（GO-COOH）was prepared by an improved carboxylation reaction，its structure was characterized and its performance of reducing pore pressure transmission and its compatibility with the drilling fluid was evaluated. The carboxylated graphene oxide was applied in the mud shale interval of Funing Formation in Yancheng area， Jiangsu. Infrared and XRD results showed that the method used in this article had successfully introduced carboxyl groups onto the graphene oxide sheet；after keeping the sample at 180 ℃ for 16 hours，the pressure transmission time of GO-COOH was 2120 s， while that of GO was only 820 s，which indicated that GO-COOH had a strong plugging ability at the high temperature. After GO-COOH was added to the polyamine drilling fluid system，it had little influence on the rheological properties of the system，and could improve its inhibition and fluid loss performance，and reduced the depth of sand bed invasion. The pressure transmission of the polyamine system was reduced from 1 MPa to less than 0.1 MPa in 50 hours with GO-COOH added，indicating that GO-COOH had good compatibility and plugging performance. The average hole diameter enlargement rate of field test wells was only 8.33%， the average accident time was only 1.03 d，and the drilling duration was 48.33 d. Compared with the pre-construction，the hole diameter enlargement rate was greatly reduced，and the downhole accident complex time was greatly reduced，and the drilling duration significantly reduced. The addition of GO-COOH had effectively alleviated the problem of borehole wall instability of the Funing Formation and produced good economic benefits.

Abstract:Special geological conditions such as oil and gas wells with CO₂ and CO₂ geological storage wells require high corrosion resistance of cement paste. In order to improve the corrosion resistance of cement paste，a waterborne resin without curing agent was selected as the anti-corrosion material. The improvement mechanism of corrosion resistance of cement paste by waterborne resin was analyzed. The results showed that the resin could effectively improve the corrosion resistance of cement paste. After 28 days of corrosion，the corrosion depth of cement paste with 15% waterborne resin was 68.7% lower than that of blank cement paste，meanwhile the compressive strength after corrosion was 12.8% lower than that without corrosion. The mixture of resin and cement slurry not only reduced the permeability of cement paste，but also reduced the large pore volume，therefore increased the corrosion flow resistance of CO₂ aqueous solution. The corrosion product formation of cement paste was reduced after resin was added into cement slurry. The microstructure of cement paste mixed with resin was denser. The film substance in cement paste increased the inertia of corrosion reaction. The waterborne resin without curing agent could improve the corrosion resistance of cement paste by reducing the formation of alkaline hydration product，increasing the penetration resistance to acid fluid and enhancing the inertia of corrosion reaction.

Abstract:Amphoteric gelling agent has the advantages of low price and convenient synthesis. It can improve the viscosity of acid based on the supramolecular effect of gelling agents. In order to construct the gelling acid system which can be applied in deep acidification fracturing well for a long time， two amphoteric gelling agents were synthesized from acrylamide （AM）， 2-acrylamide-2-methylpropanesulfonic acid（AMPS），dimethyl diallyl ammonium chloride（DMDAAC）or methacryloyloxyethyl trimethyl ammonium chloride（DMC）by free radical aqueous solution polymerization. The preparation conditions of gelling agents were optimized，and then the acid dissolving time，viscosity and temperature and shear resistance of gelling agents in acid solution were investigated. The results showed that the acid dissolving time of two amphoteric gelling agents were less than 40 min. Meanwhile，the viscosity increasing performance was good. The viscosity of acid containing the compound of two amphoteric gelling agents mixed in mass ratio 7∶3 was 39 mPa·s at 25 ℃ and 170 s^-1，while that was 15 mPa·s at 160 ℃ and 170 s^-1 after continuous shearing for 90 min. Compared with a single gelling agent，the compound gelling agent had better viscosity increasing property，temperature resistance and shear resistance performance.

Abstract:In order to reduce the cost and environmental pollution risk of fracturing operation in tight sandstone reservoir，and improve the utilization efficiency of fracturing fluid，a new composite surfactant（GEMR-2）was prepared by using fatty acid， dimethylaminopropylamine，dichloroisopropanol，non-ionic surfactant，multi-component organic solvent，etc. It was compounded with organic acid salt regulator to obtain a low damage recoverable clean fracturing fluid system suitable for tight reservoir. The comprehensive properties of fracturing fluid，such as sand carrying property，gel breaking property，damage to core and recyclability，were evaluated in the laboratory. Finally，the fracturing fluid was successfully applied in the field. The results showed that the fracturing fluid system had good temperature resistance and shear resistance，and the viscosity could still reach more than 50 mPa·s after shearing for 120 min at 80 ℃ and 170 s^-1. The fracturing fluid had strong sand carrying capacity and could break the gel quickly. The residue content of the gel breaking fluid was less than 1.5 mg/L，and the interfacial tension was low. The damage rate of fracturing fluid to the permeability of natural core after gel breaking was less than 5% ，indicating low damage. The fracturing fluid repeatedly prepared with gel breaker still had strong temperature resistance and shear resistance，and had good recyclability. The construction process using low damage recyclable clean fracturing fluid system in ZM-12 well was successful. The fracturing stimulation effect was remarkable，the repeated liquid mixing performance of on-site flow-back fluid was good，and a great deal of water resource was saved.

Abstract:In order to study the properties of drag reducing agents of hydrophobically associating binary acrylamide copolymers with different hydrophobic structures，four kinds of allyldimethylalkyl quaternary ammonium salt monomers，named as AQAS1， AQAS2，AQAS3，AQAS4，were synthesized，and four kinds of hydrophobic associated polyacrylamide P（AM/AQAS1），P（AM/ AQAS2），P（AM/AQAS3），P（AM/AQAS4）were synthesized by aqueous solution polymerization using four kinds of modified monomers with acrylamide（AM）. The solubility，salt resistance，temperature resistance and shear resistance of four products were studied，the drag reducing ability of P（AM/AQAS1）and P（AM/NaAA）was compared. The result showed that，four kinds of hydrophobically associating polyacrylamide presented good salt resistance temperature resistance and shear resistance performance. When the flow rate was 45 L/min，the drag reduction rate of P（AM/AQAS1）in NaCl solution with the concentration of 10 g/L was 60%，while the drag reducing rate of P（AM/NaAA）was 51% at the same conditon，as a result，P（AM/AQAS1）exhibited more significant drag reducing ability.

Abstract:In order to delay the gelation time of polymer gel，a micro-nano sustained-release（MNSR）gel was prepared using partially hydrolyzed polyacrylamide，crosslinking agent J₁（chromic acetate）and J₂（phenolic resin），D-isoascorbic acid and hydrophobic fumed silica as raw materials. The crosslinking agent solution was encapsulated by the self-assembly of hydrophobic particles in aqueous solution，and then added into a polymer solution，as a result，the purpose of delaying the gelation time was achieved by slowly releasing the crosslinking agent. The influence of pH value on the encapsulation ability of hydrophobic particles and the concentration of hydrophobic particles on the thermal stability of capsules，gelation time and gel strength were studied. Experimental results showed that the pH value of the solution suitable for the sustained-release capsule was 2—10. When the particle concentration in the capsule was 10%，the water separation rate of the capsule was 3.33% at 30 ℃ and 26.67% at 120 ℃ after 240 h. When the capsules with a particle concentration of 10% were used，the gelation time of the gel was extended from 48 h to 486 h at the temperature of 30 ℃，and was extended from 1 h to 144 h at the temperature of 120 ℃. The gel storage modulus G' of the gel before adding the capsule was 43 Pa and yield stress was 102 Pa，while the G' of MNSR gel was 313 Pa and the yield stress was 202 Pa. The sustained-release capsules prepared by hydrophobic particles had better thermal stability，which not only delayed gelation time，but also increased the gel strength.

Abstract:In order to solve the problem of high water cut in Fractured-vuggy carbonate reservoirs of Tahe oilfield with high temperature and high salinity，a novel self-recovery pre-crosslinked gel（SPG）with excellent resistance to high temperature（140 ℃） and ultra-high salinity（240 g/L）had been developed through dissolving HPAM，methenamine and hydroquinone thiourea in high salinity brine，and inorganic CCH was added to improve stability. Rheological properties and microstructure of SPG had been characterized，while plugging performance of gel was measured using cubic fractured core. Results showed that 3D network structure of bulk gel system was fuller and tightness，the period of dehydration was extended. The initial viscosity of SPG was 77.1 mPa·s，and the strength of bulk gel system could be stabilized at the H—I level，the dehydration rate of bulk gel system was only 5% within 30 days. The plugging rate of cubic fracture core was above 90%. The SPG had good injection，shear resistance and erosion resistance，exhibiting application potential in fracture-vuggy carbonate reservoirs with fully-developed fractures.

Abstract:In order to effectively deal with the leakage or escape that may occur after CO₂ storage，a CO₂ responsive gel with excellent injectability and good sealing effect was prepared. The sol-gel state transition occurs under acidic conditions，which was suitable for CCUS geological storage conditions and could improve wellbore integrity. The rheological properties，microstructure and sealing performance of CO₂ responsive gel with different amounts of branched polyethyleneimine （1.5% —3.5%） and κ-carrageenan（0.4%—0.5%）were studied. The study showed that the viscosity of the system before the response decreased with the increase of the shear rate，and the system was a pseudoplastic fluid. When the shear rate was 100—1000 s^-1，the viscosity was 2—100 mPa·s，indicating that the system had good injectability. The polymer system undergoed a sol-gel state transition when it encountered CO₂. The modulus of the pre-response system was in the range of 10-5 —100 Pa when the shear frequency was 0.01—10 Hz；while the modulus of the CO₂ responsive gel was in the range of 80—4000 Pa when the shear frequency was 0.01—10 Hz. The modulus of the system after the introduction of CO₂ was greatly improved. After the response，the system had a three-dimensional network skeleton structure with smooth surface and uniform pore size，so that the system had high strength. The results of the core flooding experiment showed that the plugging rate of the F system（the amount of κ-carrageenan was 0.5%，the amount of branched polyethyleneimine was 3.5%）for CO₂ gas was 79.7% and the plugging rate for the water phase was 99.8%，exhibiting good anti-gas channeling performance. This paper provided a new technical route and theoretical basis for the application of CO₂ responsive gel channeling agent in the field of CCUS geological storage in the future.

Abstract:In order to avoid a large amount of fluid leaking into the reservoir during well cleaning and causing damage to oil and gas reservoir，the clean shielding temporary plugging agent（CSTPA）was prepared using natural resin and polyol as the main raw materials. Then a CSTPA system was prepared by mixing CSTPA，sodium dodecyl benzene sulfonate，dispersing mutual solvent and other additives. The solubility，compatibility，optimum dosage and parallel plugging and de-plugging performance of the system were studied. The results showed that the temporary plugging agent could be completely dissolved in oil solvent. It had good compatibility with formation water and water source water. The optimum dosage of plugging agent was 50%. The plugging rate to core could reach 96.24% and the plugging rate was 93.59%. Furthermore，the scouring resistance was strong. The field effect of the clean shielding temporary plugging system was good. The daily average oil production was increased from 2.4 m³ to 3.6 m³，the water cut，meanwhile，was reduced to a certain extent，which indicated that the system could achieve the purpose of oil and gas reservoir protection.

Abstract:In order to explore the cause of serious emulsification of the Jimsar crude oil，the crude oil was separated into three components，including colloid，asphaltene，and remaining components，using precipitation and chromatographic separation methods.The elemental analysis of the crude oil and colloid was determined by elemental analyzer. The molecular composition of the heavy oil and the colloid was identified by electrospray technology（ESI）combined with high-resolution Fourier transform ion cyclotron resonance mass spectrometer（FT-ICR MS）. The results showed that the colloid content of the crude oil was 43.19%，the asphaltene content was 0.31% and the residual content was 56.5%. The elemental analysis results showed that the nitrogen content in the colloid was about 2.3 times as high as that of the crude oil，the content of O and S in colloid was 1.82 and 1.29 times as high as that of crude oil，indicating that the main emulsifying active components of Jimsar crude oil came from colloid. In the -ESI mode，the relative molecular weight of non-alkaline compounds was within 200—600 Da and the mass center of crude oil and colloid is at m/z= 350. The molecular structure type and relative abundance of various compounds in the mass spectrum were then analyzed. The content relation of each component in the mass spectrum was，N₁>N₁O₁>N₁O₂>O₂>O₁. It is speculated that the higher content of carbazole（N₁）compounds leaded to the increase of the emulsification and water-binding capacity of the crude oil；in addition，N₁O₁ and N₁O₂，the oxidation products of N₁，increased the hydrophilicity，polarity and emulsification of the crude oil. The structure of O₂ （acid）and O₁（phenol）was also analyzed. Their existence further enhanced the emulsification ability of the crude oil. In the +ESI mode. The molecular weight of the alkaline compounds of Jimusar crude oil and its colloid was within 200—600 Da. The mass center of crude oil was at m/z=350，while the mass center of colloid was at m/z=340. In the +ESI mode，there were two types of nitrogen-containing heteroatoms，N₁ and N₂，of which N₁ domained the absolute predominance，which may be compound of octahydroacridines，octahydrophenanthridines，quinolines or isoquinolines. Such substances enhanced the emulsifying ability of crude oil under acidic，neutral or high temperature conditions. It was inferred that the main cause of the serious emulsification of Jimusar shale oil was the polar components in the colloid，which had high interfacial activity and were easily adsorbed on the interface to promote the reduction of interfacial tension and the increase of interfacial membrane strength，hence was conducive to the stable existence of the emulsion.

Abstract:Rock wettability has an important effect on delaying the rise of water cone after the water cone is pressed in bottom water reservoir，but the degree of influence is not clear. Therefore，four kinds of wetting agents with different wetting abilities were preferred with the contact angle as an index. The wetting agents were dissolved in oil-soluble viscosity reducer，then the effects of the viscosity reducing system on viscosity reduction of heavy oil and inhibition of water cone rise again were evaluated. The internal relationship between wettability and production physical condition was quantitatively described. The action mechanism of the wetting agent was analyzed. The results showed that the four wetting agents had no effect on the viscosity reducing performance of viscosity reducer. The reservoir under the action of lipophilic wetting agent had the best effect of restraining the rise again of bottom water. The equilibrium pressure ratio reached 3.75，meanwhile the net recovery degree was increased by 15.17%. However，the equilibrium pressure ratio of the reservoir under the action of a strong hydrophilic wetting agent was only 0.54，meanwhile the net recovery degree was increased by 6.51% . There was obvious regularity between wettability and recovered physical property. Adjusting the wettability of reservoir could effectively restrain the rise again of water cone，and therefore improve the oil recovery.

Abstract:In order to meet the needs of enhanced oil recovery in low-permeability reservoir，a new type of nanoemulsion was developed as an oil-displacing agent. Its interfacial property，wettability，temperature and salt resistance were evaluated. The oil displacement efficiency of the nanoemulsion oil-displacing agent was investigated by magnetic resonance，relative permeability experiment and spontaneous imbibition experiment. At the same time，the performance of oil-displacing agent was compared with that of conventional sulfonate surfactant. The results showed that the average particle size of the nanoemulsion oil-displacing agent was 60 nm. When the mass fraction of the nanoemulsion oil-displacing agent increased，the surface tension of solution and oil-water interfacial tension gradually decreased. When the dosage of oil-displacing agent was 0.2%，the oil-water interfacial tension could reach 2.94×10^-3 mN/m，showing good interfacial activity. At the same time，it could change the core surface from lipophilicity to hydrophilicity，realizing wetting reversal. When the dosage of nanoemulsion oil-displacing agent was 0.2%，the emulsification efficiency to crude oil could reach 98% . The nanoemulsion oil-displacing agent had excellent temperature resistance and salt resistance. The static imbibition could increase oil recovery by more than 30 percentage points. The application of fracturing flooding in Xinjiang oilfield and water injection huff and puff in old wells showed that the nano imbibition flooding technology had better stimulation effect than conventional flooding technology. When the liquid production was not much different，the flowback rate was lower，while the oil production was higher. The oil displacement replacement effect was better.

Abstract:In view of the practical problems of low permeability and high salinity reservoirs in Yanchang oilfield，such as poor salt tolerance of conventional foam injection and bad oil displacement efficiency，a viscoelastic carbon dioxide foam flooding system was studied in this paper. Based on the self-assembly characteristics of surfactants，the main foaming agent，auxiliary foaming agent，stabilizer and complexing agents were screened out in formation water without alkali and polymer. The formulation of 0.20% UCAB + 0.20% SDS + 0.09% triethanolamine + 0.08% EDTA was determined by single factor method. Under the optimized condition，the viscosity of the foam flooding system was 15.2 mPa?s，the foaming volume was 560 mL，the half-life was 58 min， and the improved foam composite index（IFCV）was 370272 mL?min?mPa? s. Metallographic microscope showed that the bubbles were irregular polygons such as pentagonal or hexagonal，indicating that the viscoelastic carbon dioxide foam had the general bubble characteristics. The viscoelasticity test showed that the small molecules formed wormlike micelles by self-assembling，and wormlike micelles entangled and associated with each other，macroscopically reflecting the viscoelasticity of polymer. Therefore， the foam flooding system not only met the injectivity，but also displayed the viscous and elastic oil displacement characteristics of polymer，which could enhance oil recovery effectively.

Abstract:In order to construct the highly stable foam for foam flooding，the influence mechanism of gas/liquid properties on foam stability was clarified from the perspective of liquid film permeability. The foam film permeability，foaming capability，elution half-life and foam half-life of seven foaming systems were evaluated using N₂ and CO₂ as gas medium by the bubble reduction method. The results showed that for the same gas，the more the number of hydrophobic carbon chains contained in the surfactant molecules，the stronger the interactions existed between surfactant molecules on the liquid film，and the smaller the foam liquid membrane permeability became. The liquid films permeability of CO₂ foam was 1—3 times as high as that of N₂ foams，so the stability of CO₂ foam was lower than that of N2 foam. There was a good correlation between the foam permeability and the foam half-life. As the liquid membrane permeability increased，the CO₂ foam half-life decreased rapidly.

Abstract:In order to clarify the law of oxygen consumption during air or oxygen-reduced air flooding，the static oxidation experiment was used to emulate the oxygen consumption process in single-factor and multi-factors oxidation reactions of crude oil under actual reservoir conditions，then quantitative characterization of the static oxygen consumption was obtained. What’s more， slimline air flooding experiment was performed to analyze the law of dynamic oxygen consumption on-way. The results showed that the oxygen consumption due to the low-temperature oxidation（LTO）reaction of crude oil would decrease the total pressure of the system. The oxygenation and bond-breaking reactions of hydrocarbon occurred to produce CO₂ and CH₄. As per the calculation from the process of oxygen consumption in actual reservoir stratum，oxygen of LTO consumption occupied 87.84% of the total consumption，dissolve in water occupied 6.3%，while oxygen consumption of the reducing substances in formation water and core was 5.86%. Moreover，consumption of on-way oxygen occurred，meanwhile the propelling in front of oxidation was observed. Relatively high temperature and pressure as well as the saturation of oil would intensify the degree of LTO，thus increasing oxygen consumption. The conclusion provided a reference and guidance to the safe and efficient application of air/oxygen-reduced air flooding in the reservoir.

Abstract:Tai 18-38 well area in Daqing has the characteristics of low reservoir permeability and strong heterogeneity，as a result， the development effect of water flooding is greatly affected，and thus further technical measures to enhance oil recovery are urgently needed. Aiming at the problems in Taibei Development Zone of Daqing，the experiment research and mechanism analysis of the seepage characteristic and transmission capacity of common polymer and salt-resistant polymer solution were carried out. The results showed that compared with ordinary polymer，salt-resistant polymer had larger molecular aggregate. The retention level in the core pores，especially in the area near the injection end，was high. As a result，the increase of seepage resistance，pressure difference and differential pressure ratio in this area were relatively large. The transmission and migration capacity was poor. Unlike ordinary polymer，salt-resistant polymer had a small amount of flaky structures on its molecular chains. So the entanglement between polymer chains was enhanced，the size of molecular aggregate was increased，then the transmission and migration capacity of polymer was poor. When the permeability of target reservoir was 238×10^-3，246×10^-3 and 255×10^-3 μm²，the corresponding polymer was medium，medium and high score polymer，and high score polymer，respectively. When the reservoir permeability was 500×10^-3 μm²，the suitable polymer was super high score and salt-resistant polymer.

Abstract:Aiming at the problems of unsatisfactory injection production ratio in actual oil production and development process of Hua182 well group in Yanchang Oilfield，low production and low energy of development wells，the failure of conventional surfactant causing by high salinity，high calcium and magnesium ions in formation water，a system of surfactant flooding with salt resistance was prepared. Without chelating agent and stabilizer，the system of surfactant flooding consisted of ampholytic gemini surfactant（PPM-12），sodium lauryl polyoxyethylene ether sulfate（AES-12）and dodecyl dimethylamine oxide（OB-2）. The ratio of the compound surfactant was optimized，and then its performance was evaluated. The results showed that the suitable mass ratio of PPM-12，AES-12 and OB-2 was 4∶1∶1—1∶1∶4 when the optimum total dosage of surfactant was 0.3%. Under these condition，the oil-water interfacial tension could reach 10-3 mN/m. It could reach the lowest value（1.2×10^-3 mN/m）when the optimum mass ratio of the three surfactants was 2∶1∶3. The adsorption，emulsification，salt resistance and oil displacing efficiency of the compound surfactant was good. The oil-water interfacial tension was still in the order of 10^-3 mN/mafter six adsorption on the surface of core. It could reach the order of 10^-3 mN/m in the concentration range of calcium and magnesium ions in oilfield. Magnesium ion had the greatest influence on the interfacial tension of the system，followed by calcium ion and sodium ion. When the dosage of oil displacement system was less than or equal to 0.25%，the emulsification water separation time was less than or equal to 2894 s. Meanwhile，the oil-water interface was clear. The average recovery increment of compound surfactant flooding system in high salt and low permeability reservoir was 10.3%. The compound surfactant flooding system had good application prospect in similar reservoirs.

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

Abstract:In order to study the influence of clay mineral content on the oil displacement efficiency of ternary composite flooding in three types of reservoirs in Daqing，using natural cores with similar porosity and permeability but different content of clay，oil displacement experiment was developed. The core before and after the experiment was analyzed by X-ray diffraction and nuclear magnetic resonance. The emulsified particle size of the produced fluid was also tested. The results showed that with the increase of clay mineral content，the range of oil recovery improved by alkali-surfactant-polymer（ASP）flooding increased first and then decreased. When the clay mineral content was 9.5%，the recovery of ASP flooding had the largest growth rate（15.7%）. There was obvious emulsification in the produced solution. When the clay mineral content increased from 2.3% to 9.6%，the emulsion changed from water-in-oil type to oil-in-water type. The particle size kept decreasing. The higher the clay mineral content，the easier migration of kaolinite in mineral was. It made the pore throat of the core larger. A specific seepage channel formed，leading to the poor water flooding effect and the reduction of ultimate recovery factor. The content of clay mineral had a great influence on the oil displacement efficiency of ASP flooding in Daqing oilfield. The oil recovery degree of water flooding and ASP flooding was affected mainly through changing the type of emulsion in produced liquid，particle size and the size of core pore throat after mineral migration. As a result，the final recovery factor was changed.

Abstract:In order to improve the demulsification effect of the crude oil emulsion from Bohai Sea S oil field，styrene-maleic anhydride copolymer（SMA） was synthesized from styrene and maleic anhydride radical polymerization，the polybranched water-soluble demulsifier TS-Z806 was synthesized by graft copolymerization of SMA and 1.0 G PAMAM，the main chain being of polystyrene-maleic anhydride copolymer，and the side chain being of 1.0 G PAMAM. The demulsification effect of the demulsifier on crude oil emulsion at different temperatures of 50—90 ℃ was investigated，and compared with that of polyether demulsifier JM-01，the demulsifier was used for the first time in Bohai Sea S oil field. The results of laboratory and field tests showed that the demulsification effect of polyether demulsifier JM-01 on crude oil emulsion was worse when the temperature was higher than 70 ℃ However，TS-Z806，a non-polyether demulsifier，still had good demulsification effect on crude oil emulsion at the higher temperature. The demulsifier TS-Z806 had shown excellent demulsification performance in treating the produced fluid containing polymer at the confluence of the crude oil comprehensive pipelines in Bohai Sea S oilfield. The demulsifier could obviously improve the water quality of the demulsified water，and the emulsified layer of the upper oil was lower after demulsification，the emulsified layer after dehydration decreased by about 69% . The demulsifier could realize the high-efficient treatment of the polymer-containing produced liquid，and had a good field application prospect.

Abstract:Aiming at the problems of expensiveness and pollution of physical and chemical demulsifiers in the process of oilfield sewage demulsification，it is advisable to study and synthesize green and environmental friendly demulsifiers. Glycolipid biosurfactant-producing T strain microorganism was cultured aerobically in the medium for 6 d， then the fermentation centrifugation supernatant was mixed with water to prepare centrifugation supernatants with different volume ratios. The supernatant was used as a solvent. A biosurfactant（BS）-stabilized nano iron sol was prepared by a combination of sol-gel and solvothermal methods. The nano iron sol stabilized by BS was characterized by scanning electron microscopy，X-ray diffraction，infrared spectroscopy，laser particle size analyzer and Zeta potentiometer. The factors affecting its morphology，size，phase，functional group，sol stability and particle size distribution were studied. The demulsification performance of the nano iron sol on the oily sewage emulsion prepared by the oil-water mixture on Weizhou Island was investigated. The results showed that when the volume fraction of supernatant was 80% and 100%，the iron particles with a particle size of about 200 nm and 40—200 nm could be synthesized，respectively. The Zeta potential electronegativity of the iron sol prepared with 20% supernatant was the strongest. The colloidal stability was the highest. When the volume fraction of supernatant was 60%，the nano iron sol product had the best demulsification effect. It could produce a good demulsification effect on the oil-in-water emulsion formed by sodium dodecyl sulfate at low temperature. After standing for 24 h，the dehydration rate reached 78%. The demulsification effect on the sewage at the Nanhai terminal site was obvious. It was recommended to combine biological metabolite with chemical agent and prepare environmental friendly composite nano demulsifier，meanwhile，study their reuse and other issues in the future.

Abstract:The incompatibility between injected water and formation water often leads to serious sulfate scaling in offshore oilfield. In order to effectively prolong the squeeze life of scale inhibitor，the adsorption enhancer was added in the pre-liquid to improve the adsorption amount of scale inhibitor in the formation and reduce the desorption rate of scale inhibitor. The quaternary ammonium salt surfactant dodecyl trimethyl ammonium chloride（DTAC）and cationic Gemini surfactant amide Gemini quaternary ammonium salt（GS-A6）were selected as the adsorption enhancers，and sodium polyacrylate（PAAS）as the scale inhibitor. The compatibility between adsorption enhancer and scale inhibitor，the static adsorption experiment and dynamic adsorption-desorption experiment were carried out. The results showed that at 120 ℃，the compatibility between the two adsorption enhancers and scale inhibitor was good，and the adsorption capacity of scale inhibitor in the formation could be increased to more than 3 times. When the oil saturation increased from 0 to 80%，the squeeze life of PAAS decreased from 1500 PV to about 1300 PV after DTAC pretreatment. Under different concentrations and oil saturations，GS-A6 had a squeeze life of more than 1500 PV，which was suitable for the scale prevention of oil wells in different development stages. Compared with DTAC，GS-A6 had the advantages of low critical micelle concentration and high surface activity，which prolonged the squeeze life of scale inhibitor and improved the oil displacement effect.

Abstract:In order to develop safe and efficient extractant and meet the requirement of safety production in oilfield，the feasibility of extracting oil-based drill cuttings by using hydrophobic deep eutectic solvent（DES）was investigated. Firstly，the hydrogen bond donor and hydrogen bond acceptor of DES were studied by stirring extraction. Then，taking the oil content of extracted drilling cuttings as the indicator，the processes of stirring extraction，ultrasonic extraction and microwave extraction were optimized. The experiment results showed that the best DES was the combination of lauric acid and thymol with the molar ratio of 0.8∶1. Among the three extraction processes，the ultrasonic extraction process was relatively mild. The oil content of the extracted cuttings could be reduced to less than 1%. The specific process was recommended as follows：6∶1 the mass ratio of DES and oil-based drill cuttings，30 min ultrasonic extraction time，and 40 ℃ extraction temperature. Under this condition，the oil content of cuttings could be reduced to 0.88%.

Abstract:Relative permeability is an important basic measurement parameter in heavy oil development experiment. Due to the high viscosity of heavy oil，oil-water emulsification is easy to occur during water flooding，which makes it difficult to obtain the heavy oil-water relative permeability curve accurately. The traditional measurement method of relative permeability curve has the disadvantages of low measurement accuracy and less information. In order to accurately measure the heavy oil-water relative permeability curve，the artificial sandstone long core was selected，the heavy oil and formation water of Bohai B reservoir were calibrated at the same time based on low field nuclear magnetic resonance measurement technology. The unsteady state method was used to measure the heavy oil-water relative permeability curve. The results showed that the pore volume（147.18 cm³），bound water saturation（25.9%），residual oil saturation（43.83%）and oil and water content at the outlet of core were accurately obtained by T₂ spectrum test of the produced liquid in the core and at the outlet，meanwhile the heavy oil-water relative permeability curve was obtained more accurately. Through the D/T₂ two-dimensional spectrum test of the produced liquid with oil-water emulsification， it could be more accurate to judge whether the oil-water emulsification occurred. The research results could provide some theoretical guidance for the heavy oil development by water flooding，which was beneficial to the exploitation mechanism study of heavy oil by water flooding.

Abstract:In view of the shortcomings of poor anti-interference ability in the detection of compound surfactants by UV spectroscopy，using hydroxypropyl-β-cyclodextrin（HP-β-CD）as the masking agent，a modified UV spectroscopy method was established to accurately detect the content of NP-40 in the compound system of alkylphenol polyoxyethylene ether（NP-40）and sodium dodecyl sulfate（SDS）. The results showed that SDS could not only enhance the absorbance of NP-40，but also reduce the critical micelle concentration c_cmc of NP-40/SDS complex system. After adding SDS，the absorbance of 0.25 mmol/L NP-40 increased from 0.345 to 0.378，an increase of 9.6%. When the concentration of SDS were 0.20 mmol/L and 0.50 mmol/L，the c_cmc of NP-40/SDS decreased from 0.237 mmol/L to 0.227 mmol/L and 0.224 mmol/L，respectively. The results also showed that HP-β-CD had remarkable anti-interference effect on the detection of NP-40 in NP-40/SDS complex system by UV spectroscopy. After HP-β-CD was added at the molar ratio of 1∶1，the absorbances of 0.25 mmol/L NP-40 and its absorbance in 0.50 mmol/L SDS solution were 0.379 and 0.381，respectively，with a variation of only 0.8%. After adding HP-β-CD，the content of NP-40 in the complex system could be accurately detected by UV spectroscopy，and the recovery rate was 99.09%—100.00%. NP-40 entered the cavity of HP-β-CD molecule and formed a 1∶1 inclusion complex，which was the main reason why HP-β-CD could eliminate the interference of SDS on NP-40 in the complex system.

Abstract:Temporary plugging operation plays a crucial role in preventing leakoff during oil/gas exploitation. In comparison with mechanical shielding procedures such as temporary blocking ball，packer and coiled tubing，chemical temporary plugging have been more thoroughly explored and more commonly applied due to their the intrinsic merits such as easy operation，low cost and direct function in the reservoir crack. Chemical tempoary plugging agents are usually categorized into particulate，fiber-pattern， gel-pattern，surfactant and even multi-complex temporary plugging systems，based on their distinct shapes，patterns and composition. This paper reviewed the progress，mechanisms，characteristics and applications of conventional chemical temporary plugging agents. Simultaneously，the demerits needed to be solved urgently and future prospects of plugging systems were also analyzed.

Abstract:In-situ crude oil emulsification often occurs in chemical flooding. Emulsification plays a positive role in enhancing oil recovery. Due to the complexity of pore-throat structure and remaining oil distribution，in-situ crude oil emulsification has its own characteristic. Based on the research results of crude oil in-situ emulsification in chemical flooding in recent years，the status and development trend were investigated from the in-situ emulsification mechanism of chemical flooding，rheology and stability of emulsion，emulsion seepage characteristic and improving oil recovery mechanism. The in-situ emulsification mechanism of crude oil and exploiting experience were analyzed from the field test of chemical flooding. The numerical simulation considering emulsification formation mechanism，emulsification degree and rheological property of emulsified crude oil，and the optimization design of chemical flooding injection scheme based on emulsification mobility control were the key research direction of chemical flooding in the future. It could provide theoretical guidance for the optimization of chemical agent and injection parameter of chemical flooding.

Abstract:In order to explore the reasons for the difficulty in the dehydration of acidified crude oil，through reviewing the experiments on the influence factors of acidified crude oil dehydration in recent years and the existing acidified crude oil dehydration technology，demulsification mechanism of crude oil affected by pH value，temperature and solid particles was summarized，the adaptability of the dehydration technology was concluded. The thermal chemical settlement method is suitable for treating crude oil with viscosity and low moisture content. The significant practical application effect of ultrasonic demulsification dehydration of thick oil shows that it can be used as an auxiliary of thermal chemical settlement process for demulsification. The water washing can remove some solid particles and acidified slag and is suitable for pre-treatment before gravity settlement. The high frequency pulse electrodesiccation is efficient in dehydration of acidified oil and aging oil，which is suitable for fine dehydration treatment. The microwave demulsification is still under research，thus the demulsification mechanism would be further studied and the industrial practical effect need to be verified. Suggestions for future research on demulsification and dehydration processes of crude oil are also provided.