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 core-shell nano plugging agent（CLG-NM）with high temperature resistance was prepared by using inorganic nano silica as the core and poly（styrene-butyl acrylate-acrylic acid）as the shell in mass ratio 10∶2∶1 through emulsion polymerization method. 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 transferring experiment. The results showed that the particle size distribution of CLG-NM was 40—300 nm，and the median particle size was 89.4 nm. CLG-NM maintained good thermal stability below 372 ℃. Furthermore，CLG-NM had good compatibility with oil-based drilling fluid. 3% CLG-NM had little effect on the fluidity of oil-based drilling fluid. The high temperature and high pressure filtration decreased from 3.1 mL to 2.8 mL after aging at 180 ℃ for 16 h，and the demulsification voltage kept higher than 700 mV. CLG-NM could enter the nano pores and fractures in the shale for plugging. The upstream pressure of oil-based drilling fluid contained CLG-NM could penetrate the core for 19.5 h. Compared with similar products at home and abroad，CLG-NM had better plugging effect on nano pores and fractures in shale.

Abstract:To overcome the inadequacies of drilling fluid in low temperature environment in the southern margin of Junggar basin，a drilling fluid system was formulated using -35^# diesel oil，freezing point being of -38 ℃，as a continuous phase. Through regulating the dosage of emulsifier，viscosifier，wetting agent，and organophilic clay，a high-density oil-based drilling fluid suitable for low temperature environments was prepared，and the fluid performance was evaluated at both low temperature（-10— -2 oC）and high temperature（180 oC）with respect to rheology，resistance to contaminants，and plugging performance. The results revealed that the fluid could not only meet the requirements of the preparation at the temperature as low as -10 ℃，but also meet satisfactorily rheological requirements under complex underground conditions that the temperature was 180℃ and density was 2.5 g/cm³ . The drilling fluid possessed stable emulsifying properties，demulsification breaking voltage being above 1000 V，and strong tolerance to contaminants. Moreover，the drilling fluid had good plugging performance，the plugging pressure was 7.0 MPa when the slit width was 0.5 mm. The drilling fluid can be successfully prepared at low temperature environmental condition in the southern margin of Junggar basin and can meet the performance requirements of the underground conditions.

Abstract:Aiming at the failure of existing fluid loss agent in the environment of high temperature and high salinity，a polymer microsphere was synthesized through inverse emulsion polymerization by water-soluble monomers，such as sodium p-styrene sulfonate with benzene ring structure and sulfonic acid group，2-acrylamide-2-methylpropanesulfonic acid and acrylamide，and oil phases，such as sorbitan fatty acid ester（Span 80），polyoxyethylene sorbitan monostearate（Tween 60）and liquid paraffin. Infrared spectroscopy，thermogravimetric analysis，scanning electron microscope and laser particle size analyzer were used to characterize the product. Then the swelling performance，salt resistance，aging performance，temperature resistance and plugging performance in the core were studied. The results showed that the microspheres displayed a spherical morphology with a particle size of 2.82—10.26 μm，and began to decompose at 270 ℃. It was found that the final expansion ratio of microspheres in deionized water was nearly 5 times the size of the previous one after reaching the swelling equilibrium. Microspheres exhibited a good fluid loss reduction performance in high salinity and high temperature conditions，and had good anti-aging property. A good plugging performance was observed in core plugging experiments. The polymer microspheres aggregated in macropores，where effective plugging was achieved.

Abstract:The surface of rubber particle has poor hydrophilicity and poor cementation with cement，which will reduce the compressive strength of cement stone during cementing. In order to improve the shortcomings of existing technology，a heterogeneous granular material was prepared by diphenylmethane diisocyanate，polyepoxypropane glycol，silicate aqueous solution and heavy calcium carbonate. Its structure was characterized. The cement slurry or cement stone was prepared by adding multiphase particles into the cement. The rheology and stability of the cement slurry and the mechanical property of the cement stone were evaluated. The results showed that there were two main structures in multiphase particles. The first phase was a porous continuous phase，and the second phase was spherical. In the multiphase particles，the second phase embedded in the pores of the first phase，and the spherical second phase contained 19.6% Si. Compared with the cement stone，the cement stone containing multiphase particles had low elastic modulus and basically maintained its strength. Multiphase particles had little effect on the thickening time and rheology of cement slurry. The spherical structure at the interface of multiphase particles contained a large number of silicon hydroxyl groups，which participated or partially participated in the hydration of cement，and was closely connected with cement at the interface by chemical bonds，so as to ensure the continuity of cement hydration structure and made up for the defect of insufficient interfacial adhesion between rubber elastic particle and cement stone.

Abstract:In view of the current low efficiency of reuse of water-based fracturing flowback fluid，A reusable water-based fracturing fluid RFrac-H was prepared used a hydrophobic associative polymer BT1218 as a thickener，and dodecylbenzenesulfonate and triethanolamine as a viscosity accelerator FJ-1，Na₂CO₃ as pH regulator，KCl as clay anti-swelling agent，sulfamic acid and persulfate as composite breaker，and RFrac-H gel breaker was also used to prepare new fracturing fluid，and the temperature resistance，shear resistance and gel breaking performance of the fracturing fluid were evaluated. Experiments results showed that when the temperature rose from 30 ℃ to 120 ℃，the viscosity of RFrac-H fracturing fluid，composed of 0.4% BT1218+0.1% Na₂CO₃+0.5%KCl+0.30% FJ-1，was greater than 50 mPa·s at the shear rate of 170 s^-1；the viscosity of the above fracturing fluid was greater than 40 mPa·s after continuous shearing for 60 min at the temperature of 100℃ and at the shear rate of 170 s^-1，and its static settlement velocity of suspended sand was 0.0214 cm/s. After breaking，the viscosity of the breaker fluid was 2.51 mPa·s，the surface tension was 24.4 mN/m，the interfacial tension was 0.282 mN/m，and the clay anti-swelling rate was greater than 80%. The performance of the fracturing fluid prepared by RFrac-H breaker fully met the requirements of fracturing fluid performance indicators，and the breaker fluid could be reused several times，which could reduce the cost of liquid preparation notably. Compared with RFrac-H，the fracturing fluid prepared by using breaker fluid had a reduction of more than 70% in the amount of thickener and viscosity accelerator.

Abstract:The Baikouquan formation in the Mahu 1# well area is a typical tight oil reservoir with low porosity and permeability. Large-scale hydraulic fracturing in this well area faces three major problems，such as poor drag reduction effect of fracturing fluid， great damage to reservoir，scarce water resource and difficult treatment of oilfield sewage. Furthermore，the remaining oil distributes between fractures，and the recovery rate needs to be improved. In response to these problems，the drag reducer（JHFR） was prepared by dispersion polymerization using hydroxymethyl styrene，vinyl acetate，acrylamide，polyvinyl benzyl trimethyl ammonium chloride，etc. Then JHFR was compounded with the multifunctional additive（JHFD）to obtain a slick water fracturing fluid. The effects of fracturing water source and the clay mineral content of reservoir rock in target block on the hydration and swelling performance of clay in slick water were studied. And the damage of slick water to the Mahu tight oil reservoir was evaluated. The results showed that the dissolution time（15 s）of drag reducer JHFR was short，and direct mixing could be realized without mixing. The slick water composed of 0.1% JHFR and 0.2% JHFD had the characteristics of high drag reduction（76.9% drag reduction rate），low oil-water interfacial tension（0.89 mN/m），good anti-swelling effect（81.12% anti-swelling rate），etc. The system had good compatibility with the formation water and flowback fluid in the Mahu 1# well area，and had low damage to the core permeability. It was suitable for the large-scale continuous fracturing in this well area.

Abstract:The overall profile control and water shutoff construction measures based on the injection-production unit can further improve the water control and oil increase effect of multiple rounds of heavy oil reservoirs in the Gaoqianbei block. In order to deeply study the relevant mechanism of overall profile control and water shutoff to improve the effect of water injection development，the indoor dynamic and static experimental evaluation was carried out to optimize the foam and gel formulation system，and the performance of control flooding and plugging was evaluated. A three-dimensional physical model of the five-point injection-production well pattern was established indoors，and a comparative experiment of foam flooding and "foam + gel" overall profile control and water shutoff to improve oil recovery was carried out to evaluate the water control and oil enhancement effects of different measures. The experimental results showed that the overall profile control and water shutoff increased oil recovery rate by 22.04%，which was 4.15% higher than that of pure foam flooding. "Foam + gel" could effectively suppress the channeling of high-permeability layers，and adjust the water absorption and liquid production profile of the well. The plane and longitudinal extent of subsequent water flooding was expanded，the heterogeneity of the reservoir had been effectively improved. The overall development effect of the injection-production well pattern had been significantly improved after the overall profile control and water shutoff construction.

Abstract:Water injection development in low permeability reservoir generally results in serious channeling of injected water and a large amount of remaining oil. Polymer microspheres and low salinity water are proven effective approaches for profile control and oil displacement in hydrocarbon reservoirs. The former focuses on profile control while the latter favors oil displacement，and thus their combination is expected to achieve the dual effect of profile control and oil displacement. This paper evaluated the effects of simultaneously injecting nano-polymer microspheres and low salinity water via core floods. Nuclear magnetic resonance T₂ spectrum and imaging test were used to reveal the extent of residual oil in pores of various sizes during core flooding as well as the mechanism of oil displacement. The results showed that the microspheres could eliminate water channeling and change flow direction，forcing the low salinity water to enter smaller pores and improving the sweep and oil displacement efficiency. The lower the salinity，the higher the produced oil from small and medium-sized pores. Increasing the concentration of microspheres and decreasing the salinity of injected fluid could enhance the plugging effect of microspheres，resulting in enhanced injection pressure and oil recovery. This study confirmed the potential of synergistic flooding with low salinity water and nano-polymer microspheres in improving oil recovery in low permeability reservoirs.

Abstract:According to the characteristics of Changqing low permeability reservoir，polymer microsphere and surfactant compound profile control and oil recovery technology was proposed. Polymer microsphere was prepared by acrylic acid， 2-acrylamide-2-methylpropanesulfonic acid，2-mercaptobenzoic acid，ammonium persulfate and sodium bisulfite. Surfactant complex system was prepared by alkanolamide polyoxyethylene polyether sulfonate and coconut oil fatty acid diethanolamide. The oil-water interfacial tension of surfactant and surfactant/polymer microsphere mixture was studied，the profile control and displacement performance of polymer microsphere and mixture was investigated，and the injection mode of compound flooding was optimized. Finally，it was applied on Ansai oilfield. The results showed that the initial particle size of polymer microsphere was generally 50—300 nm. It had hydration expansion characteristic with expansion ratio of 20—100 times. The aggregation characteristic of microspheres during hydration and expansion was observed by SEM. The microspheres had good dispersion and sphericity，and the particle size distribution was Gaussian normal distribution. The most economical concentration of surfactant was 3 g/L. The viscosity of the mixture increased after adding surfactant to polymer microsphere，and the dispersed phase particle of microsphere shielded the interfacial activity and micelle formation ability of surfactant，which resulted in the decrease of interfacial tension and was not conducive to surfactant flooding. Polymer microsphere solution had good plugging performance to core. When the mass concentration of microsphere was greater than 4 g/L，the plugging rate was about 80%. The oil displacement efficiency of polymer microsphere and surfactant by slug injection mode with volume ratio of 1∶1 was better than that by mixed injection of two systems. The application effect of this technology in Ansai oilfield was good，and the cumulative oil increase was 3576 t.

Abstract:In order to solve the problems faced by the current profile control and flooding combination technology in Bohai oilfield，and promote the oil increasing effect，BZ34-2/4 reservoir was taken as the simulation object，and the injection parameters and combination mode of profile control and flooding of phenolic gel/polymer microspheres were the optimized by the simulated experiments in heterogeneous cores. The results showed that phenolic gel，consisted of 3 g/L polymer，3 g/L phenolic resin crosslinking agent and 3 g/L resorcinol curing agent，had higher gelation strength and good plugging effect on high permeable layer. Supramolecular polymer microspheres with concentration of 3 g/L had good hydration swelling effect，which could achieve macro and micro fluid diversion effect. With the increase of core heterogeneity，water flooding recovery decreasesd，and the oil recovery of profile control and flooding presented a trend of "increase first and then decrease". From the technical and economic point of view，the reasonable injection timing of profile control and displacement control was 80%—90% of water cut，and the reasonable slug size of profile control agent was about 0.10—0.20 PV，and the reasonable slug size of flooding agent was about 0.20—0.30 PV. Compared with large slug and integral injection，small slug and multiple rounds of alternate injection could reduce the retention of microspheres at the injection end and slow down the inversion speed of profile，so as to improve the effect of fluid diversion.

Abstract:With the increasing attention to environmental protection and reservoir protection in domestic oil fields，the green non-toxic self-degrading temporary plugging agent has become a research focus in recent years. A new self-degrading water-soluble temporary plugging agent was developed by combining two kinds of self-degrading materials and the formula was 60% PA+40% YG-1. The solubility，compatibility，plugging-property，compression resistance，dispersion and suspension performance and influence on fracturing fluid performance of the temporary plugging agent were studied. The composition of the temporary plugging agent hydrolysate was analyzed，and the temporary plugging agent was applied in Changqing low permeability reservoir. The dissolution rates of the temporary plugging agent in formation water，liquid preparation water and fracturing fluid within 8 hours were all more than 95% and the compatibility was good. The plugging rates of the temporary plugging agent to fractured core were more than 80% at the temperature of 50—80 ℃. The broken rate of the temporary plugging agent was less than 10% at 40 MPa. The temporary plugging agent had good dispersion and suspension performance in guar gum base solution. The temporary plugging agent hydrolysate，which contained only glucose and glycollic acid，had little influence on the rheologic property of fracturing fluid and was environment-friendly. The new temporary plugging agent had been successfully applied in 32 wells in a middle and high water-cut block of Changqing low permeability reservoir. The results showed that the new temporary plugging agent could effectively increase the fracture net pressure and open new fractures. Compared with the conventional temporary plugging agent， the new temporary plugging agent had better stimulation effect and the advantage of environmental protection.

Abstract:The glutenite formation of Kunbei oilfield has large thickness and severe heterogeneity in planar direction，inter-layer and intra-layer. In the early stage of development，the horizontal wells show the characteristics of high decline of production and rapid rise of water cut，so water control is urgently needed. Based on the reservoir features and wells production performances，the terpolymer was prepared using acrylamide，2-acrylamide-2-methylpropanesulfonic acid and dimethyldiallyl ammonium chloride for selective water shutoff in horizontal well. The effects of crosslinking agent N，N- methylene bisacrylamide on the strength and swelling rate of water shutoff agent were studied. The injection performance and plugging ability of water shutoff agent were investigated. On the basis of laboratory experiment and well performance，the oilfield trials of water shutoff for 6 horizontal wells were carried out in Kunbei oilfield. The experiment results showed that the amount of crosslinking agent had great influence on the strength and swelling rate of water shutoff agent. When the dosage of crosslinking agent was 1.5% of the total mass of monomer， the strength of water shutoff agent was moderate. It could be stretched，and the swelling rate reached the highest. The average size of water shutoff agent particle was 420 μm，which could form effective plugging in the fracture of Kunbei reservoir. After injecting water shutoff agent into sandpack column，the injection pressure of subsequent water flooding increased by 5.06 times，and the plugging rate of water flooding was 83.5% and that of oil flooding was 20%，showing a good selectivity to oil and water. The water shutoff agent was applied in Kunbei oilfield and the remarkable effect of increasing oil and reducing water was gained.

Abstract:Aiming at the problem of high injection pressure caused by particle migration and the blocking of reservoir pore throat in the water injection process of loose low permeability sandstone reservoir with high content clay，a neutral gradient anti-plugging system was optimized through laboratory experiments. The lower speed gradient anti-plugging system consisted of 0.5% KCl clay stabilizer，and the higher speed gradient anti-plugging system consisted of 0.2% KCl and 0.3% organic cationic clay stabilizer （YN）. The anti-swelling performance of the 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 about 91%. Compared with blank produced water（0.75 mL/min）displacement，at a lower speed（0.25 mL/min），the pressure growth multiple was reduced from 5.41 to 2.03 after 0.5% KCl displacement，and the permeability retention rate was increased from 18.49% to 49.15%. At higher speed（0.50 mL/min），the core permeability was gradually restored after displacement by 0.2% KCl and 0.3% YN system. After produced water displacement of 8 PV by 0.75 mL/min，the permeability retention rate was increased from 10.56% to 91.58%，and the pressure growth multiple was reduced from 9.47 to 3.28. Through the synergistic effect of velocity gradient and plugging prevention system，obvious plugging prevention and pressure reduction effect was obtained.

Abstract:Nanoparticles have a good application prospect in enhancing oil recovery due to its unique nano-effects，but the ultra-low permeability reservoirs have small pore throats，and the adsorption of nanoparticles has a greater impact on the physical properties of the reservoir. Based on the displacement experiments of SiO₂ nanofluids in the ultra-low permeability cores，combined with the ultraviolet-visible spectrophotometer，the adsorption capacity of nanoparticles in cores was tested，and the core slices after displacement were observed by scanning electron microscope. The research results showed that when mass fraction of nanofluids increased from 0.01% to 0.50%，the core injection pressure increased，and the retention rate of nanoparticles increased，being of 7.60%—87.50%，as a result，the permeability loss rate could reach up to 96.46%. The subsequent displacement of NaCl solution only took away a few unstably adsorbed free nanoparticles，but did not alleviate the adsorption obviously，because of the formation of effective plugging in the rock core. In order not to affect the subsequent injection of fluids，the mass fraction of SiO₂ nanofluids injected into ultra-low permeability sandstone should not exceed 0.01%. The scanning images of core sections after displacement demonstrated that the nanoparticles were concentrated on the pore throat and matrix surface at the front of the core，occupying the fluid seepage channel，which caused structural changes in the pore throat. As the concentration of nanofluids increased，the particle aggregation phenomenon became more obvious.

Abstract:To solve steam overriding and steam channeling in steam flooding, sulfonate surfactant ZAS, polyether sulfonate surfactant ZCP-1 and nanoparticle NS were compound to found a three-phase foam system with temperature resistance of 300 ℃ which formula was 0.5% ZAS/ZCP-1（mixed proportion was 3∶1）+1.0% NS. Then evaluated its foam performance, temperature resistance, plugging performance and oil displacement performance was evaluated through experiments. The results showed that the three-phase foam system had excellent foam performance at room temperature, the foam volume was 680 mL, the liquid half-life was 26.67 min, and the foam half-life was 12 h, and it was stable after heat aging at the temperature of 300 ℃. The three-phase foam system could stably exist at a high temperature condition of 300 °C and had blocking ability to selectively seal high permeability layers. Its resistance factor was greater than 30 within the permeability range of 1000×10^-3—4000×10^-3 μm² , meantime, its blocking ability increased with the increase in permeability. Under the heterogeneous condition with a permeability difference of 1∶2, it could improve the total oil recovery by 17.93%, as a result of adjusting the steam absorption profile and increasing the oil recovery of the low-permeability model. The three-phase foam system has good potential to improve the oil recovery of steam flooding.

Abstract:Aiming at the serious problems of steam channeling for steam flooding，the combination of high-temperature channeling plugging agent and oil displacement agent were prepared. The high-temperature-resistant channeling plugging agent was prepared with tannin extracts system，the sulfonate surfactant and anionic-nonionic surfactant were compounded to obtain high-temperature oil displacement agent，then the compound profile-control and oil displacement technology of channeling plugging agent and oil displacement agent on improving the recovery rate of steam flooding was investigated by heterogeneous double-tube physical simulation experiments. The results showed that the plugging rate of high temperature tannin extracts plugging agent could maintained above 90% after 15 PV of steam flooding flushing at the temperature of 250 ℃ ，exhibiting significantly plugging properties. After aging at 300 ℃，the high temperature oil displacement agent SLB/CY（2∶1）could still reduce the oil-water IFT to below 0.001 mN/m. In the experiment of heterogeneous double-tube by steam flooding of heavy oil，the combination of channeling plugging agent and oil displacement agent could effectively plug the steam channeling of high permeability tube and ensure the subsequent injection of oil displacement agent into low permeability tube，which could improve the final comprehensive oil drive efficiency by 23.58% and effectively improve the development effect of steam flooding in heterogeneous formation.

Abstract:Hydrodynamic radius is an important parameter to evaluate polymer injection ability. By counting the product quality test results of the same series of ordinary polymers（partially hydrolyzed polyacrylamide）and hydrophobically associating polymers， measuring the hydrodynamic radius of the corresponding polymers，and analyzing the relationship between polymer Huggins constant and performance parameters，a method for qualitatively evaluating the hydrodynamic radius of the same series of polymers was obtained. The change of Huggins constant was related to the molecular structure and functional groups of the polymer. Under certain conditions，the Huggins constant of partially hydrolyzed polyacrylamide increased exponentially with the increase of degree of hydrolysis，the Huggins constant of hydrophobically associating polymer increased linearly with the increase of viscosity，and a few polymers with dissimilated molecular structure deviated from the above change law. Therefore，according to the product quality test results and the relationship between Huggins constant and performance parameters of the two polymers，the hydrodynamic radius could be compared and evaluated easily and accurately.

Abstract:In order to improve the polymer flooding effect of class II reservoir in land B oilfield，taking the characteristics of target reservoir and fluid properties as the research object，the best injection parameters and injection methods suitable for the target reservoir were optimized by carrying out the indoor displacement experimental of heterogeneous core model in the layer. The experimental results showed that，with the increase of polymer molecular weight and solution concentration，the size of polymer molecular aggregates increased，the resistance coefficient and residual resistance coefficient increased，but due to the influence of core pore throat shear，the amplification of residual resistance coefficient gradually decreased. It could be seen from the oil displacement experiment that the influence of polymer injection viscosity on the production effect was as follows，gradient viscosity increasing > alternating viscosity changing > gradient viscosity decreasing > single high viscosity > single low viscosity. Among them，the oil recovery of gradient viscosity increasing，alternate viscosity changing and gradient viscosity reducing was enhanced by more than 20%，and the oil recovery of gradient viscosity increasing was the best，being of 24.2%. The influence of polymer injection rate on production effect was as follows，gradient speed increasing > single high speed > alternate speed changing > gradient speed decreasing > single low speed. Among them，the oil recovery of the gradient speed increasing and alternating speed changing was enhanced greatly，and oil recovery of the gradient speed increasing was 25.6%. Under the condition that the injection slug size was fixed，the increasing effect of oil recovery under different combination injection methods was as follows：speed increasing and viscosity reducing > speed decreasing and viscosity increasing，and the enhanced oil recovery under the combination of speed increasing and viscosity reducing was 28.6% . It could be seen that the combination of changing injection speed and viscosity at the same time in the process of injection was better than that of single changing speed or viscosity.

Abstract:Surfactant imbibition is an important method to enhance crude oil utilization in tight oil matrix. In order to reveal the characteristics of surfactant imbibition to enhance crude oil utilization in matrix-fracture model of tight oil，0.05% cocamidopropyl sulfobetaine（ASB）was selected as the surfactant for percolation by measuring spontaneous imbibition，interfacial tension and wettability. The effects of fracture tortuosity and intra-seam flow velocity on the dynamic imbibition of near-seam matrix to improve crude oil utilization characteristics were investigated by matrix-fracture core model and microfluidic model，respectively. And the effects of surfactant depth and concentration on the spontaneous imbibition of deep matrix to improve crude oil utilization characteristics were investigated by static imbibition experiment. The results showed that the degree of crude oil recovery by dynamic imbibition of near-fracture matrix increased with increasing tortuosity of the model. The more the fracture complexity，the higher the degree of dynamic imbibition recovery was. The bigger the flow velocity in fracture，the bigger the migration rate of oil-water interface in capillary was. That was，the bigger the imbibition rate was. And the migration rate of oil-water interface and the flow velocity in fracture conformed to the law of quadratic function as a whole. The deeper the surfactant action depth，the lower production of crude oil per unit volume was. When the concentration of surfactant was high，the variation law of the degree of spontaneous imbibition production was consistent with the interfacial tension as the main control parameter of capillary force was interfacial tension. While the concentration of surfactant was low，the main control parameter of capillary force was the wettability of rock surface. At this time，the variation law of the degree of spontaneous imbibition and production was opposite to the interfacial tension.

Abstract:Aiming at the problems of low water flooding recovery and high thermal recovery cost in Shengli normal heavy oil reservoir，emulsion viscosity reduction flooding is an effective way to improve recovery and reduce production cost. In this paper， considering the emulsifying ability and reducing interfacial tension of two surfactants TB and AC in different ratios，two kinds of emulsion flooding systems with different properties，TB（0.3%）and TB + AC（0.3%，mass ratio of 3：2），were constructed by using micro dynamic emulsification experimental device. The micro stability of the emulsion formed by the two systems and Shengli heavy oil was analyzed by multiple light scattering method. Then，the oil displacement performance of the two emulsifying systems was evaluated by sand-filled tube oil displacement experiment，and the microscopic oil displacement mechanism was studied by glass etching model. The research results showed that the TB + AC system possessed strong emulsification and the obtained emulsion was stable. The TB+AC system could make oil-water interfacial tension decrease to 10^-3 mN/m. TB+AC system could enhance oil recovery by 11.20% based on water flooding. The system could "pull" the residual oil through ultra-low interfacial tension and strong emulsifying properties to deform it and reduce flow resistance and residual oil content. In addition，the oil film could also be further emulsified to expand and break the film to enhance oil recovery.

Abstract:In order to make the treated gas field water meet the national secondary discharge standard，the corrosion inhibitor CPI-W was firstly added to the simulated gas field water to investigate the effect of corrosion inhibitor on chemical oxygen demand （COD）in gas field water，and then the simulated gas field water added with corrosion inhibitor CPI-W was treated by sodium hypochlorite method，Fenton's reagent method and potassium persulfate-ferrous sulfate method to investigate the COD removal effect，respectively. The results showed that all three treatment methods were able to achieve COD values of simulated gas field water spiked with 1000 mg/L corrosion inhibitor to meet the secondary discharge standard（<150 mg/L）of the comprehensive wastewater discharge standard. After treatment by sodium hypochlorite oxidation method，the COD removal rate reached 94.4% when the sodium hypochlorite dosage was 8 mg/L；after treatment by Fenton's reagent method，the COD removal rate reached 96.1% when the H₂O₂ dosage was 4 mg/L and FeSO₄·7H₂O dosage was 0.08 mg/L；while after treatment by potassium persulfate-ferric sulfate method，the COD removal rate was 97.4% when K₂S₂O₈ was added at 8 mg/L and FeSO₄·7H₂O was added at 4 mg/L. Comparing the COD removal rate and the cost of chemicals，the potassium persulfate-ferrous sulfate method was the best method to degrade the corrosion inhibitor in gas field wastewater among the three advanced oxidation techniques.

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 reverse demulsifier to improve the separation efficient of oil and water. The acrylate-methacrylic acid copolymer emulsion reverse demulsifier（EMASA）was synthesized via emulsion polymerization method by using ethyl acrylate，methacrylic acid and stearyl acrylate as precursors. The structure of EMASA was characterized，and its water purification performance was investigated by bottle test method with oil removal rate as the main index. Finally，the field pilot test was carried out on the platform A of offshore oilfield，and the reverse demulsification mechanism of EMASA was analyzed. The results showed that the actual structure of synthesized product was consistent with the theoretical structure，and the thermal decomposition temperature of EMASA was 214.5 ℃. The water purification effect of EMASA was excellent. The oil removal rate under optimal injection amount（30 mg/L）was 96.5%，and the value further increased to 98.9% under the help of synergistic flocculant. In the field pilot test，when the dosage of EMASA was 30 mg/L，the oil content in outlet water of separator decreased from 255.75 mg/L to 197.58 mg/L，with a decrease of 22.74%，and the oil removal rate increased from 95.5% to 96.52%. EMASA used two effects such as rolling sweep and destroying the strength of oil-water interface film to achieve oil and water separation. The effect was obvious in the treatment of produced fluid with sodium bicarbonate water-type.

Abstract:Because the heavy oil emulsion is opaque，it is impossible to intuitively understand the influence of sand particle on the stability of heavy oil emulsion. Scholars had detected the asphaltenes adsorbed on the surface of mineral particles by Fourier transform infrared spectroscopy. It was speculated that these particles destroyed the strength of oil/water interfacial film due to the adsorption of asphaltenes on the oil/water interfacial film and promoted the aggregation of water droplets，so as to realize the demulsification and stratification of heavy oil emulsion. However，this understanding couldn’t explain some phenomena in this experiment. In this paper，experiments such as bottle experiment，rheology test and wettability test were carried out，and the influence mechanism of quartz sand on the stability of heavy oil emulsion was studied. The results showed that when the particle size of sand was small and the particle size of water droplet was large，the phenomenon of water droplets completely wetting and wrapping the sand particles would occur. Furthermore，the proportion of water droplets wrapping sand particles increased，and the settlement speed accelerated. This was the main reason for the demulsification and stratification of heavy oil emulsion by sand，and this understanding was also verified by the sedimentation experiment of sand in white oil.

Abstract:The scaling of pipelines and storage tanks in Zhenyuan oilfield is very serious，and there are no effective anti-scaling measures. Firstly，the water types of two water samples in He 53 and Yan 116 in Fangshan operation area of Zhenyuan oilfield were analyzed，and then the scaling trend of mixed water samples was predicted by using the scaling prediction software OLI ScaleChem， which was verified by indoor experiments. Carboxymethylated inulin calcium carbonate （CaCO₃） scale inhibitor CMI，and strontium sulfate（SrSO₄）scale inhibitor P（MA/MMA）was prepared. The anti-scaling performance of the P（MA/MMA）and CMI on mixed water was studied，and its anti-scaling machine was analyzed. Results showed that there were lots of scaling ions in He 53 and Yan 116 water in Fangshan of Zhenyuan oilfield，and there were scaling tendency when they are mixed. Prediction results showed that when the volume ratio of He 53 to yan116 water was 8∶2，the scale amount was as high as 587 mg/L，and the scale types were CaCO₃ and SrSO₄. The experimental results were basically consistent with the predicted results. The scale inhibition rate of compound scale inhibitor CQ-SI，the mass ratio of CMI to P（MA/MMA）bening of 4∶6，could be as high as 93.5% when the dosage was 150 mg/L. CQ-SI inhibits the formation of scale by forming chelates with scaling cations，and plays an excellent anti-scaling effect by dispersing and separating scale samples.

Abstract:To meet the requirements of hydrogen sulfide removal in offshore oil field，using a new dynamic evaluation system， which was suitable for simulation analysis of the actual desulfurization efficiency of the desulfurizer，new desulfurizers were developed and the effect of working parameters on site on the desulfurization efficiency was analyzed. The experimental results showed that，the desulfurization efficiency of the synthesized multi-compound H₂S scanvenger 11# obtained when the molar ratio of methylamine，monoethanolamine and diethylamine was 1∶1∶1，maintained above 96% during the experiment，exhibiting excellent desulfurization efficiency and the largest sulfur capacity. The desulfurization efficiency of H₂S scanvenger 11# decreased with the increase of gas-liquid ratio. The desulfurization efficiency firstly increased and then decreased with the increase of the speed of the high gravity device，while increased with the increase of the total pressure of the system. The system temperature had little effect on the desulfurization efficiency. Field tests showed that desulfurization efficiency of H₂S scanvenger 11# was obviously better than that of the original H₂S scanvenger 0#，which further reduced the corrosion and safety risk on site.

Abstract:Aiming at the disadvantages of traditional titration detection method such as low sensitivity，poor anti-interference ability and long detection period，a detection method for α-olefin sulfonates used in oilfield was established by liquid chromatography tandem quadrupole mass spectrometer. By optimizing the detection condition，the quantitative detection of olefin sulfonate in olefin sulfonate product，injection fluid and output fluid was realized. The results showed that the optimum detection condition was obtained as follows：anionic chromatographic column，mobile phase contained methanol and 8 mmol/L ammonium acetate aqueous solution in volume ratio 55∶45，isocratic elution. The mass spectrometry detection condition was obtained as follows：electrospray ion source，negative mode，30 psi atomizing pressure，8 L/min dry air velocity，350 ℃ dry gas temperature，full scan. The recovery rate of this method for olefin sulfonate product，injection fluid and produced fluid was 82.63%—96.37%，78.60%— 95.41% and 82.68%—95.72%，respectively. One sample detection was completed in 8 minutes. Meanwhile，polymer and trace oil had little effect on the detection result. This method was fast，sensitive and had strong anti-interference ability.

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 organic treatment agents in water-based drilling fluid，such as rheology modifier，filtration loss reducer，shale inhibitor，lubricant and lost circulation control materials were described. According to the characteristics of different organic treatment agents in intelligent drilling fluid，the application feasibility of intelligent materials in water-based drilling fluid was discussed，and the research ideas，methods and application prospects of organic treatment agents in intelligent drilling fluid system were prospected.

Abstract:In recent years，the research on environmentally friendly lubricants for drilling fluids has developed rapidly. In this paper，the types，mechanisms of action and the latest research progress of environmental lubricants used in drilling fluids at home and abroad were reviewed，and a variety of biological toxicity evaluation methods suitable for lubricants were compared. In order to ensure the accuracy of environmental protection indicators，it was recommended to conduct multiple evaluation methods at the same time and to achieve both EC₅₀ and LC₅₀ data. The development trend of environmentally friendly lubricants in the future was analyzed，especially for the high-efficiency，environmentally friendly and high-temperature resistant lubricants，and the future research prospects of synthetic ester lubricants was predicted.

Abstract:The thermochemical reaction of the chemical in-situ heat generation fracturing fluid（CISHGF）occurs at a low pH or high temperature to produce a salt solution and gas with low damage to the formation，and release a lot of heat. The CISHGF exhibits large heat generation，fast flowback and low reservoir damage，etc.，and effectively solve the problems including fracturing fluid cooling damage to the formation and incomplete gel breaking at the lower temperature. The heat generation mechanisms of ammonium chloride and sodium nitrite were introduced，and the effects of pH，reactant concentration and initial temperature on the heat generation and heat generation reaction rate of fracturing fluid were analyzed；According to different crosslinking agents，the CISHGF were divided into boron cross-linked guanidine gum fracturing fluid，acidic cross-linking fracturing fluid and viscoelastic surfactant fracturing fluid，and the performance，advantages and disadvantages of different fracturing fluid systems were summarized，The fracturing process and field applications were introduced. In view of the problems existing in the current system，the prospect of CISHGF the fracturing fluid formulation and process was expected.

Abstract:The reservoir heterogeneity are the key factors restricting the improvement of oil recovery and are the important and difficult points in the development of oil and gas fields. The control and flooding of crosslinked polymer microspheres is an important technical means to solve this problem. However，with the development of more and more oil and gas fields with low permeability，deep sea，high temperature and deep well in recent years，the complex pore structure of low permeability reservoirs and the environment of deep sea，high temperature and deep well need higher requirements for the performance of microsphere injection，plugging，penetration，temperature and salt resistance. In this paper，the control and flooding mechanism of microspheres，preparation methods，research progress in indoor oil displacement effect and field tests，and the existing problems were mainly introduced. On this basis，the future research on microspheres were proposed.

Abstract:Nanoparticles are seen as potential advanced materials to overcome the challenges，such as low sweep efficiency， associated with these traditional enhanced oil recovery（EOR）techniques. It sorted the application of nanoparticles augmented chemical EOR，gas EOR，and thermal EOR techniques in recent years，introduced the main principles，characteristics and research results of nanoparticles augmented EOR process，and indicated the EOR challenges and trend using nanoparticles.