Abstract:In the drilling process of deep-water oil and gas fields，due to the low temperature near the bottom mud line，it is easy to appear thickening，plugging and slurry running of drilling fluid. In order to solve the problem，the thermosensitive thickening copolymer（ASSN）was prepared from acrylamide，N-vinyl caprolactam，divinylbenzene and sodium allyl sulfonate. Then the flow pattern regulator with constant rheological properties at low temperature was prepared by mixing ASSN with fenugreek gum. The solid-free constant rheological drilling fluid with reservoir protection for deep-water drilling was prepared by mixing flow pattern regulator with other treatment agents. The performance of ASSN，flow pattern regulator and drilling fluid was evaluated. The results showed that the critical association temperature of ASSN solution was 27 ℃. When 0.5% ASSN and 0.3% fenugreek gum were used as flow pattern regulators，the viscosity of the aqueous solution was stable in the range of 4—60 ℃ . The flow pattern regulator played a good role in regulating the rheology of drilling fluid at low temperature. The weighting agent had little effect on the control ability of drilling fluid at low temperature. The flow pattern regulator had good compatibility with other treating agents of drilling fluid. The drilling fluid had good anti-fouling performance，inhibition performance，lubrication performance and reservoir protection performance，which could meet the requirements of field drilling.

Abstract:In order to reduce the harm of commonly used chain transfer agent during the preparation of zwitterionic polymer viscosity reducer，using acrylic acid （AA），2-acrylamido-2-methylpropanesulfonic acid （AMPS），and methacryloxyethyl trimethylammonium chloride（DMC）as monomers，environmentally friendly tetramethylthiuram disulfide（TMTD）instead of sulfhydryl compound as chain transfer agent，a zwitterionic polymer viscosity reducer with low molecular weight for drilling fluid was synthesized through the aqueous solution explosion polymerization process. Taking the viscosity reduction rate at room temperature as the evaluation index，the synthesis condition of the viscosity reducer was optimized，and then its viscosity reduction performance was evaluated. The results showed that，the optimum synthesis condition was obtained as follows：0.75% TMTD，3% oxidation-reduction initiator in total mass of monomer，50% NaOH in total molar amount of AA and AMPS，44% AA，5.5% AMPS and 4.5% DMC. Under this condition，the number average molecular weight of the synthesized zwitterionic polymer viscosity reducer was 914 g/mol. Its viscosity reduction rate in fresh water base slurry was 91.53%. The viscosity reducer had good temperature resistance，which met the temperature resistance requirement of 180 ℃ . The preparation method reduced the environmental pollution caused by the synthesis process of zwitterionic viscosity reducer with low molecular weight.

Abstract:Most of the current temperature-sensitive thickeners are not suitable for high depth reservoirs due to their poor temperature and salt resistance. A self-prepared thermo-sensitive macromonomer（PADA），2-acrylamide-2-methylpropanesulfonic acid （AMPS），N，N-methyl bisacrylamide （MBA） and modified nano-silica （N-np） were used to prepare a kind of nano-silica-thermo-thickening composite N-AMPA by in-situ polymerization. The synthesis conditions of N-AMPA were optimized by orthogonal experiment. The molecular structure of N-AMPA was evidenced by FT-IR and 1H-NMR，and the thermo-thickening behavior，high temperature stability and shear resistance of N-AMPA solution was investigated. The results showed that N-AMPA possessed showed thermo-thickening behavior property in the temperature range of 65—180 ℃，the maximum thickening rate was 94%. The viscosity retention of N-AMPA solution was 68% after high temperature aging at 200 ℃. In 20% NaCl saline solution， the viscosity retention rate was 63%. When the shear rate was 1021 s^-1 ，the solution viscosity reached up to 50 mPa·s. Compared with temperature-sensitive polymer AMPA solution，N-AMPA showed good temperature resistance，salt resistance and strong shear resistance.

Abstract:Conventional inhibitors could not effectively control the hydration of clay surface，which caused wellbore instability. An intercalation adsorption inhibitor with high temperature resistance was prepared by introducing sulfonic acid group into tetraethylene pentamine as reaction monomer. The structure of the inhibitor was characterized and its performance was evaluated. The mechanism of intercalation adsorption inhibitor with high temperature resistance was further analyzed. The results showed that there were a lot of strong adsorption groups and hydrophobic groups in the molecular structure of new inhibitor，which had low molecular weight， non-toxic environmental protection and good thermal stability. The analysis of inhibition mechanism showed that the electrostatic repulsion and short-range repulsion of clay surface hydration could be effectively reduced by the combination of strong adsorption group and exchange of hydrated sodium ions. By reducing the surface tension of aqueous solution and changing the wettability of clay，the self-imbibition capacity and specific hydrophilicity of shale could be controlled，and then the invasion of water phase was reduced. Meanwhile，the new inhibitor had strong adsorption and anti-desorption ability，which could adsorb on the clay surface for a long time，improve the hydrophobicity of the clay surface，and reduce the invasion of free water. The new inhibitor had good properties of inhibiting mud production，controlling clay hydration expansion and preventing shale dispersion，which was superior to polyamine inhibitors at home and abroad.

Abstract:In view of the characteristics of shale gas plugging in Sichuan and Chongqing block，such as high pressure and easy backflow，the anti-backflow plugging agent（ARP）was developed with high softening point resin as the main body. The dispersion of ARP plugging agent in the field oil-based drilling fluid and the bonding strength with the field plugging agent were evaluated in the laboratory. Its pressure-bearing capacity and anti-backflow capacity after cementing and solidification were tested. The results showed that the best formula of ARP plugging agent was obtained as follows：epoxy resin（softening point 90 ℃），iron ore powder，20% diethyl toluene diamine. When the density of the plugging agent was 1.8 g/cm³ and the particle size was 0.5—2.0mm，it had good dispersion in the field oil-based drilling fluid. ARP plugging agent had the ability of deformation，cementation and solidification. When ARP plugging agent was used in combination with bridge plugging particle，it could cement and solidify with other ordinary plugging particles in formation fractures，thus improving the pressure bearing capacity and anti-backflow ability of the overall plugging slug. When ARP plugging agent was combined with field plugging agent，the appropriate proportion of ARP was 15%—25%. Meanwhile，the cementing strength of the composite plugging agent could reach 2.7—7.8 MPa. When the lost circulation slurry prepared by ARP was used to seal fractures with 2—3 mm width，the positive pressure bearing capacity could reach 8 MPa，while the anti-backflow pressure bearing capacity could reach 3.3 MPa. According to the characteristics of materials， the site construction technology was designed and applied in a well in Changning，Sichuan. A good plugging effect was achieved.

Abstract:When shale gas reservoir is developed by horizontal wells，due to casing eccentricity and irregular diameter，the displacement efficiency of oil-based drilling fluid is usually low. Some oil-based drilling fluid is mixed into cement slurry，which affects the performance of cement slurry. In order to improve the anti-pollution ability of shale gas cementing cement slurry，the surfactant （AFSG-1） was prepared by mixing non-ionic surfactant and anionic surfactant in the laboratory. The research on improving the anti-pollution performance of shale gas well cementing cement slurry by AFSG-1 was carried out with the field oil-based drilling fluid and cementing cement slurry as the research object. The results showed that the addition of oil-based drilling fluid in the field would seriously affect the fluidity，thickening time and mud-mixed water and debris properties of cement slurry. The greater the proportion of oil-based drilling fluid，the more serious the pollution was. With the increasing amount of AFSG-1 in cement slurry，the anti-pollution ability of cement slurry was gradually enhanced. When the mass fraction of AFSG-1 in cement slurry was 2%，and then 20% oil-based drilling fluid was added，the fluidity，thickening time and cement stone properties of the slurry were significantly improved compared with those without surfactant. In addition， the anti-pollution performance improvement effect of AFSG-1 on oil-based drilling fluid of cement slurry was significantly better than that of other commonly used surfactants. AFSG-1 could effectively improve the ability of shale gas cement slurry to resist the pollution of oil-based drilling fluid， improve the cementing quality and ensure the cementing safety.

Abstract:In order to improve the stability of the acid microemulsion under high formation temperature，a micro-emulsified acid microemulsion was developed with 0# diesel as the oil phase，20% hydrochloric acid as the water phase，the fixed water-oil ratio was 7∶3，and the total addition of microemulsifier SMT-3 and co-emulsifier SRA-5 was 15.5%，through investigating the effect of the mass ratio of SMT-3 to SRA-5 on the temperature and salt resistance of the acid microemulsion and its static and dynamic properties of the acid microemulsion with mass ratio of SMT-3 to SRA-5 was 0.5∶1 were thoroughly investigated. It was found that the developed acid microemulsion，which showed an average particle size of 30 nm，could remain stable at the temperature of 100 ℃ for at least 10 hours. It was also able to withstand the Ca²⁺ as high as 20%. It remained clear and transparent after sheared for 2 hours under the shearing rate of 170 s^-1 ，demonstrating its outstanding shear resistance. As the acid droplets were well separated by the oil，the acid microemulsion presented much lower corrosion rate on N80 steel slide and much slower dissolution rate on limestone，compared to those of hydrochloric acid and thickening acid with identical concentrations. The rotating disk experiments indicated that the reaction rate of the acid microemulsion was only 1/30 of that of hydrochloric acid，which enabled it to penetrate into the deep formation. The core flooding experiments showed that the core permeability had been increased by 500% after acidification and the formation damage was negligible. Overall，the proposed acid microemulsion may be applied as an ideal acidifying fluid for high temperature limestone reservoirs.

Abstract:In view of the problems of poor acid resistance，complicated removal process and high cost of temporary plugging agent used in acid fracturing of carbonate reservoir，a kind of degradable gel temporary plugging agent with micro-expansion（WDS）for acid fracturing was prepared through aqueous radical polymerization method by using self-made quaternary ammonium ester （JD-1）as cross-linking agent. The degradation performance，plugging performance and reservoir damage of WDS were studied. Finally it was applied in HY well. The results showed that WDS was first micro-expansion and then degradation in HCl solution or aqueous solutions with different salinity. The complete degradation time of WDS in 10% HCl solution reduced from 78 h to 45 h when the temperature rose from 70 ℃ to 120 ℃ . When the mass fraction of HCl increased from 3% to 20%，the complete degradation time of WDS at 90 ℃ shortened from 75 h to 48 h. The higher the salt concentration，the longer the complete degradation time of WDS was. According to the results of core displacement experiment，with increasing injection of WDS and decreasing fracture width，the peak value of temporary plugging pressure increased，while the time reaching the maximum temporary plugging pressure reduced. In addition，WDS was less harmful to the core. The permeability recovery value of core was more than 90%. After using WDS in field application，the oil pressure was increased by 10 MPa，indicating remarkable effect of temporary plugging.

Abstract:In order to improve the injecting and plugging properties of low permeability reservoirs，a hydrogel system was developed，the formulation and preparation conditions of the hydrogel were optimized based on the gel strength，and the plugging and flooding performance were evaluated. The optimized hydrogel formula was as follows，the dosage of acrylic acid，acrylamide，ammonium persulfate，modified starch and N，N- methylene bis acrylamide was 20 g/L，5 g/L，0.07 g/L，5 g/L，0.08 g/L， respectively，and the best synthesis condition was that neutralization degree was 75%，initiation temperature was 9 ℃ .The gel strength of the obtained hydrogel was 35—37 Pa · s. Hydrogel profile control agent with micrometer size was obtained by mechanical shearing and drying. The plugging experiment showed that the plugging rate of hydrogel with the mass concentration of 0.1—0.7 g/L to the sand-filled pipe with the permeability of 1600×10^-3—1900×10^-3 μm² was more than 92%. With the increase of the mass concentration of hydrogel，the drag coefficient increased，and the injection pressure increased rapidly，but the residual resistance coefficient and plugging rate changed little. It was recommended to use low concentration injection of hydrogel as oil displacement agent，which could improve oil recovery by about 10% on the basis of water flooding. Low concentration micro particle hydrogel could effectively solve the contradiction between injectivity and plugging of profile control in low permeability reservoirs. Considering the injection and plugging and flooding properties，the recommended mass concentration of hydrogel was 0.1—0.3 g/L.

Abstract:Temperature is a key factor limiting the degradation of polymer gel. Aiming at the blockage caused by polymer gel in low temperature reservoirs，the oxidation ability of persulfate was improved by low temperature activation using persulfate as oxidation reducer. First，the activator（TA）was prepared from copper sulfate hydrate and tetrasodium iminosuccinate. Then the quenching experiment and the radical test were used to analyze the degradation mechanism of the polymer gel. Finally，the effect of persulfate concentration and TA concentration on the degradation of polymer gel at different temperature was studied. The formula of activation system was optimized. Meanwhile，the corrosivity of the system was also evaluated. The results showed that TA activated persulfate could rapidly degrade the polymer gel at 35 ℃. The superoxide anion radicals were the main active radicals in degradation reaction. With the increase of persulfate concentration，the degradation rate increased，but the concentration of TA had the optimal value，and the temperature increase could accelerate the degradation of gel. Compared with other polymer plugging removers，TA activated persulfate could rapidly degrade polymer gel with mild corrosion. At low temperature，the system composed of 0.10 mol/L sodium persulfate and 0.12 mol/L TA had better degradation effect than other conventional polymer flooding reservoir plugging agents.

Abstract:Aiming at the problems of sand production in shallow low-temperature formation and high water cut in oil wells， laboratory research on low-temperature solidified water blocking and oil permeability sand control materials was carried out. A sand control material was prepared by blending quartz sand，epoxy resin，relative permeability regulator and dispersant. The curing mechanism，thermal stability and micro morphology of coated sand and artificial core were analyzed by FT-IR，thermogravimetry and scanning electron microscope，and the compressive strength and water/oil permeability of artificial core were investigated. The experimental results showed that under the condition of low temperature of 30—70 ℃，the artificial core obtained by solidifying the sand control material with 30% relative permeability regulator had excellent compressive strength，more than 4.22 MPa. Moreover，the cores had certain oil-water selectivity，the water phase permeability and oil phase permeability being of 963×10^-3 and 5513×10^-3 μm²，respectively. The obtained sand control materials met the requirements of sand control and water resistance of low temperature shallow wells under low temperature of 30—70 C.

Abstract:Aimed at the spontaneous oil-in-water emulsified phenomenon in low acid high phenol crude oil，the components of the crude oil separated by column chromatography method were analyzed and characterized quantitatively by Fourier transform infrared spectroscopy and Orbitrap mass spectrometry. Then according to the molecular characterization of crude oil，interfacial activity between crude oil components and heavy alkyl benzene sulfonate，NaCl and NaHCO₃ solution was determined and discussed， respectively. Results showed that the relative content of phenols was higher and chain fatty acids in resins were important components in low acid high phenolic crude oil. The oil-solution interfacial tension increased significantly after the removal of petroleum acids. Phenols which had larger relative content than acids in crude oil could promote emulsification. For alkaline solution，phenols，naphthenic acids and chain fatty acids could reduce interfacial tension. However，the interfacial activity between phenols and other solution was lower. Only chain fatty acids could reduce interfacial tension.

Abstract:In order to explore the role of surfactant in dual composite system，four surfactants，such as betaine type（S1），anionic type（S2），lipopeptide biotype（S3）and nonionic-anion surfactant（S4）were combined with partially hydrolyzed polyacrylamide （HPAM）to form a dual composite system，respectively. By measuring the viscosity，oil-water interfacial tension，emulsification and core flooding experiment of the system，the mechanism of enhancing oil recovery by surfactant was analyzed. The results showed that in dual composite flooding，surfactant had a very small influence on the viscosity of system，and the polymer ultimately determined the viscosity of system. All four types of surfactants had amphiphilic structure，which could reduce the interfacial tension between oil and water to 10^-3 mN/m and promote oil-water emulsification. The recovery ratio of dual composite flooding was higher than that of single polymer flooding. S4/HPAM dual system could reduce the interfacial tension between oil and water to 2.4×10^-3 mN/m. The formed oil-water emulsion had the highest viscosity，the strongest stability and the best effect of enhancing oil recovery.

Abstract:It is a promising way to produce heavy oil with CO₂ flooding，and it is a common way to introduce various additives to assist CO₂ to further enhance oil recovery. However，it is rarely reported the interaction between smart cationic surfactant and heavy oil and viscosity reduction by emulsification. In this work，a series of surfactants，i.e.，2# —4#，were prepared by reaction of hexadecyl trimethyl ammonium hydroxide（1#）with acetic acid and carbon dioxide. Besides，the surface activity and emulsifying ability of 1# —4# surfactant for dodecane，the interfacial tension between 1# —4# solution and heavy oil and the emulsifying behavior of heavy oil were studied comparatively. The results showed that the surface activity and emulsifying ability to dodecane of 2# —4# surfactant had little change with that of 1# surfactant. However，1# surfactant had reverse emulsification for heavy oil， while 2#—4# surfactant had obvious viscosity reduction ability for heavy oil. In particular，when the reaction ratio of CO₂ was low， a“quasi-binary”surfactant（4#）could be formed with CTAOH，whose viscosity reduction rate was more than 98% and interfacial tension value could reach ultra low as 10^-3 mN/m. Meanwhile，it was found that the synthetic surfactant was temperature-responsive and the dehydration rate was faster with temperature improving. The advantage could bring the better oil displacement effect and the easier treatment of produced liquid. The results show a prospective strategy for improving the enhanced oil recovery of carbon dioxide flooding.

Abstract:The aggregation behavior of asphaltenes significantly affects the viscosity of heavy oil. Studying the aggregation behavior of CO₂ on asphaltenes in heavy oil can further analyze the action mechanism of CO₂ in the process of displacement. Under different CO₂ pressures and conditions，CO₂ dissolution experiments were carried out on heavy oil and heavy oil containing CO₂ solubilizers （benzene or ethanol）. After separating the four components，CO₂-treated asphaltenes were obtained. X-ray diffractometer，scanning electron microscope and transmission electron microscope were used to characterize the interlayer spacing，surface morphology and microstructure of asphaltene aggregates extracted under different experimental conditions. The influence mechanism of CO₂ on asphaltene aggregation behavior in heavy oil was analyzed. The results showed that the dissolution of CO₂ in heavy oil broadened the layer spacing of asphaltene accumulation and retarded the aggregation behavior of asphaltene molecules. Solubilizers increased the concentration of CO₂ in heavy oil. It played a synergistic role to further decline the aggregation probability of asphaltene molecules in heavy oil，decrease the aggregation rate of asphaltene and diminish the interaction with glial molecules，thus reducing the viscosity of heavy oil.

Abstract:In order to clarify the effect of heavy oil hydrothermal cracking temperature at 250 ℃ and 280 ℃ on the molecular structure of asphaltene and the viscosity of heavy oil under the catalysis of amphiphilic catalyst，taking Shengli heavy oil as the research object and C₁₂BSNi as the catalyst，the changes of asphaltene molecular structure before and after the reaction were analyzed by FTIR and 1H-NMR. The results showed that when the hydrocracking reaction of heavy oil occurred at the temperature of 250 ℃，the viscosity of heavy oil was greatly reduced，the viscosity reduction rate being of 60.4%，while the viscosity reduction rate decreased with the increase of reaction temperature to 280 ℃，viscosity reduction rate only being of 53.8%. As the reaction temperature increased from 250 ℃ to 280 ℃，the average side chain length of asphaltene molecules gradually decreased，but the aromaticity increased and the number of aromatic rings increased，which indicated that asphaltene molecules had undergone radical condensation reactions，and the average molecular structure of asphaltene became larger，resulting in a relatively small viscosity reduction rate. In addition，a series of bond breaking reactions occurred during the reaction of asphaltene molecules，resulting in the reduction of their steric hindrance. The smaller the asphaltene molecular unit lamella，the easier it was to accumulate. It was observed by SEM that the pore channel of asphaltene structure gradually became larger and denser with the increase of temperature， but the surface aggregated particles became larger. It provided important guiding significance for the optimization of operating conditions of heavy oil hydrothermal cracking reaction.

Abstract:In view of the exploitation needs of heavy oil reservoirs with high temperature，high mineralization，high wax content and low permeability in southern Dagang oilfield，lipophilic monomer vinyl pyrazine，tridecyl maleate and hydrophilic monomer AMPS were selected for inverse emulsion copolymerization with acrylamide，and a water-soluble double base heavy oil viscosity-reducing agent emulsion was prepared. The effect of different synthetic conditions on the esterification rate of the hydrophobic monomer was investigated，the optimized synthesis conditions of viscosity reducer were determined through investigating the influence of the amount of hydrophobic monomer，the mass ratio of each monomer，the mass ratio of emulsifiers and the amount of initiator on the viscosity reduction and emulsification effect of the synthetic viscosity reducer. The temperature resistance，salt resistance，stripping effect of heavy oil and viscosity reduction effect of several types of high viscosity heavy oil in Dagang oilfield were studied. The field test results of 3 well times of application of synthetic viscosity reducer in Dagang South Oilfield were reported. The optimum synthesis conditions of the viscosity reducer was as follows，the tridecyl maleate dosage was 0.6%，the mass ratio of theAM，AMPS， vinyl pyrazine，tridecyl maleate was 7∶1∶3∶2，mass ratio of Tween 80 and Span 60 was 1.5∶1，initiator dosage was 400 mg/L，and mass ratio of oxidant，reducing agent and azo initiator was 1∶0.5∶0.8. The viscosity reducer had a temperature resistance of 180 ℃ and a salt resistance of 50 000 mg/L. the heavy oil could be completely stripped within 22 h. after mixing in the oil-water ratio of 7∶ 3，the viscosity reducer solution with a mass fraction of 1%，prepared with produced water from different blocks，could make the viscosity of the heavy oil reduce by more than 95%. The viscosity reduction tests was carried out using the viscosity reducer in block of Dagang south oilfield，the operation of chemical huff and puff and wellbore care was adopted according to the site demand，and the effect of increasing the oil and reducing the load was obtained.

Abstract:In order to study the mechanism of percolation effect of surfactants in dense sandstone reservoirs，four different types of surfactants were tested for wettability and interfacial tension，and surfactant percolation experiments were carried out. The microscopic pore characteristics of cores were characterized by combining nuclear magnetic resonance （NMR） tests and high-pressure mercury compression experiments，and NMR tests were conducted during percolation to study the mechanism of percolation effect of different pore types. The results showed that the anionic surfactant had a stronger ability to change the wettability and reduce the interfacial tension，and the change of wettability was the key to improve the recovery rate of percolation. The pore types of dense sandstone were classified as nanopore（r ＜ 0.1 μm），micropore（0.1 μm ＜ r ＜ 10 μm），and macropore （r ＞ 10 μm），among which micropore was the main storage space of crude oil，with 67.7% of the pore volume. The recovery rate of percolation was the largest for macropore，followed by micropore and nanopore. The cationic surfactants CTAB and amphoteric surfactants BS-12 had inhibitory effect on percolation，and non-ionic surfactants APG-12 had the similar poor percolation effect， while anionic surfactants SDS and AES had the best wettability change effect. For surfactants solution，mass fraction being of 0.1%，with hydrophilic wetting of dense rocks，the shorter the wetting time（AES ＜ SDS ＜ APG-12），the greater the number of surfactants adsorbed on the surface of micro- and nano-pore throats of dense rocks，the stronger the wettability change，and the higher the surfactant percolation recovery（APG-12＜ SDS ＜AES）.

Abstract:In order to deeply understand the corrosion inhibition mechanism of thiourea-based acidizing corrosion inhibitors and improve the application effect of corrosion inhibitors in acidizing development process，the corrosion inhibition performance and corrosion inhibition mechanism of two thiourea derivatives，such as phenyl thiourea（PHTU）and benzoyl thiourea（BOTU）on 20# steel in 15% HCl solution were studied by corrosion weight loss experiment，scanning electron microscope and quantum chemical calculation. The results showed that PHTU and BOTU had good corrosion inhibition effect on 20# steel in 15% HCl solution. When the concentration of corrosion inhibitor was 2 mmol/L，the dense and complete corrosion product formed on the surface of steel sheet could inhibit the contact between corrosive medium and steel substrate. The corrosion inhibition rate could reach more than 83%. Moreover，with the presence of C=O double bond in BOTU molecule，the corrosion inhibition performance of BOTU was better than that of PHTU. The adsorption of both PHTU and BOTU on steel surface was in accordance with the Langmuir adsorption model. The adsorption mode was a mixture of physical and chemical adsorption coexisting. Quantum chemical calculations showed that the reactive sites in corrosion inhibitor molecule mainly distributed on C=S double bond，C—N bond and C=O double bond of BOTU. Nitrogen atoms protonated by the acid could form physical adsorption with steel surface through electrostatic gravitational attraction. The C=S bond，C=O bond and phenyl group with high electron cloud density could provide electrons to form chemisorption with the empty d orbitals of Fe atoms through coordination and feedback bonding，which in turn stabilized the adsorption on metal surface to form a protective film and inhibit the corrosion process.

Abstract:In order to further optimize the operation of natural gas pipeline，the natural gas drag reducer 1，3，5-benzenetricarboxylic acid tridodecylamide（BATD）was synthesized from 1，3，5-benzenetricarboxylic acid，p-toluenesulfonic acid，dodecylamine，etc. Its performance of drag reduction and corrosion in natural gas pipeline transmission was comprehensively evaluated by using atomization time and BATD dosage as variables，along with scanning electron microscopy. The results showed that BATD could firmly adsorb on the steel surface，significantly reduce the roughness of the steel surface，and significantly improve the transmission efficiency of the gas pipeline，and also had the effect of corrosion inhibition. When the atomization time was 60 min and BATD dosage was 6 g/L，the maximum drag reduction rate reached 13.32% and the slow release rate reached 85.12%. The film forming performance of BATD solution was good，which could reduce resistance and increase transportation.

Abstract:It is difficult to solve the problem of the degradation of organic pollutants in fracturing flow-back fluid and the treatment process is complex. In this paper，the law and mechanism of ultrasonic degradation of hydroxypropyl guar gum，which is a key contaminant in fracturing flow-back fluid，was analyzed. The results suggested that the mechanism of ultrasonic degradation of hydroxypropyl guar gum was mainly physical shearing，ultrasonic mode and power were the main controlling parameters of hydroxypropyl guar gum degradation reaction，followed by concentration. The ultrasonic time，temperature，pH value and other factors had little influence on hydroxypropyl guar gum degradation reaction. For a certain concentration of hydroxypropyl guar gum solution，the optimal degradation parameters were as follows，the duty ratio was 40%，the ultrasonic power was 360 W，the ultrasonic time was 60 min and the temperature was 25 ℃. Because temperature and pH had little influence on hydroxypropyl guar gum degradation reaction，the ultrasonic degradation technology could be applied to a wide temperature range of 5—50 ℃ and pH range of 5—11.

Abstract:In view of the difficulty of treating oily sewage in heavy oil polymer injection oilfield，phenolamine resin was synthesized using bisphenol-A，formaldehyde and triethylenetetramine as the main raw materials，and then a series of bisphenol-A phenolamine polyether clearing agents with multi-branched chain，multi-amine group and multi-phenylene ring were synthesized from phenolamine resin as the starting agent. The effect of the clearing agent was analyzed by studying the changes of oil-water interface properties before and after the addition of clearing agent. The clear water effect of the synthetic series of clear water agent was evaluated by reducing the oil content of wastewater to less than 20 mg/L within 3 min after adding clear water agent，from which clear water agent F-14 and F-15 were selected，and the clear water effect of the compounded clear water agent was investigated in different compounding ratios，and field application experiments were conducted. The results showed that the clear water agent F-14 and F-15 are compounded according to the compounding ratio of 2∶1，and the oil content of the sewage could be reduced to 18 mg/L at the dosing rate of 40 mg/L within 3 min，which met the standard requirements. the synthetic clear water agent had strong interfacial activity，which could easily adsorb at the oil-water interface and repel the original surface-active material at the oil-water interface to form a new oil-water interface film. The newly formed interface film was weak and easy to rupture， resulting in colliding between small oil droplets and gathering easy to form large oil droplets，promoting the separation of oil and water，so as to achieve the clear water effect of oily sewage. The results of the field trial in an oilfield in Bohai Sea showed that the synthetic clear water agent was suitable for short flow and polymer containing sewage quality，and the oil content in the treated injection water was below 20 mg/L，meeting the field technical requirements.

Abstract:In order to broaden the application of biomass materials in the field of oil-water separation，a kind of superhydrophobic stem fiber/chitosan composite aerogel was synthesized by a simple freeze-drying-normal temperature impregnation method using a large amount of cheap sunflower stems in Xinjiang as raw materials，chitosan as composite material，and stearic acid as hydrophobic modifier. The aerogel was characterized by FT-IR，SEM，and static water contact angle measuring instrument，and oil absorption and recycling performance were evaluated. The results showed that when the mass ratio of sunflower stem fiber and chitosan was 6∶1，the stearic acid dosage was 1.64%，and the immersion time was 2.5 h，the static water contact angle of the obtained composite aerogel was the largest，being of 150.9°. The adsorption capacity of the composite aerogel to different oils such as kerosene was 12.34—21.85 g/g，moreover，it still maintained stable oil absorption and hydrophobicity after 10 cycles of use. The research not only provides a new method for the preparation of oil-water separation materials，but also broadens the way for the high value utilization of abundant straw in Xinjiang.

Abstract:In order to improve the lubrication of water-based drilling fluid，solve the high friction of long horizontal section of horizontal wells and promote the sustainable development of drilling technology for horizontal well，a great number of researches about eco-friendly lubricant with high performance had been conducted at home and abroad. In this paper，the domestic and international research progress of lubricant for water-based drilling fluid was reviewed including alcohol ether，alkyl glycoside， modified vegetable oil，compound lubricant，inert solid，encapsulated lubricant and extreme-pressure lubricant. The advantages and disadvantages of these lubricants were compared. Finally，the development directions of lubricant for water-based drilling fluid were proposed.

Abstract:The Mannich base，quaternary ammonium salt and imidazoline type corrosion inhibitor systems applicable to the range of 90—180 ℃ were deeply investigated. The high temperature corrosion inhibitors were reviewed from five aspects：corrosion inhibitor structure，type of additives，testing conditions，corrosion inhibition effect and mechanism of action. The future development direction of the research on high temperature corrosion inhibitors for oilfield acidizing was considered from the perspective of formulation exploration and mechanism research.

Abstract:Nowadays，chemical flooding，gas injection，and heavy oil thermal recovery are the three main technologies of enhanced oil recovery（EOR）in China. In this paper，the application progress and trends of the chemical flooding，including polymer flooding，ASP flooding，binary combination flooding，heterogeneous combination flooding，etc.，were expounded.

Abstract:Chemical flooding，gas injection，and heavy oil thermal recovery are the three important technologies of enhanced oil recovery（EOR）in China. In this paper，the application progress of gas injection，and heavy oil thermal recovery were expounded， including CCUS，N₂ injection，hydrocarbon injection，and air injection in gas injection technologies，and steam flooding，steam stimulation，SAGD，thermochemistry assisted steam stimulation，in-situ combustion in heavy oil thermal recovery technologies.

Abstract:Imbibition is the main oil recovery mechanism in most low permeability reservoirs in China. The effect of imbibition oil recovery is affected by many factors，such as reservoir characteristics，oil production system，physical and chemical properties of surfactants，etc. Its mechanism of action also need to be further studied. In this paper，the mechanism of imbibition including the mechanical analysis of capillary imbibition was reviewed. The technical progress of imbibition test method was introduced. The controlling factors affecting imbibition，including rock and fluid properties，temperature and pressure，were summarized. The influence of properties of imbibition agent on enhanced oil recovery by imbibition was emphatically introduced，which played a guiding role in optimizing the selection of surfactant used for imbibition，and the existing problems in oil recovery by imbibition and the prospect of future research direction was put forward.