Abstract:In order to reveal the interaction between nano-micro particles and clay minerals in drilling process，styrene，butyl acrylate and poly（ethylene glycol）monomethyl ether methacrylate macromonomer were used to prepared ether type polymer particles by emulsion polymerization method. The chemical structure and size distribution were determined by infrared spectrometer and laser particle size tester. The effect of particle on the performance of drilling fluids was studied and the function mechanism was discussed. The results showed that the polymer particle possessed the structural characteristic of ether bond groups. The particle size distribution was narrow in the range of 0.2—1 μm and the ratio of nano and micro particle was about 2∶8. Ether type nano-micro particles had good compatibility with drilling fluid. It could be used to control the filtration of polysulfide，polymer and APG clay-free drilling fluids at temperature as high as 130℃ and improve the quality of mud cake.

Abstract:Aiming at the problems of commonly drilling fluid lubricant，such as low pressure，poor anti-friction effect and temperature resistance， extreme pressure lubricant NH-EPL was prepared by introducing metal organic compound into alkanolamine ester. The properties of NH-EPL，such as lubrication，friction-reduction and wear-resistance effect，temperature resistance and salt tolerance，foam ability，fluorescence level and biological toxicity and so on，were studied and the effect of NH-EPL on the rheological property of drilling fluid was investigated. Furthermore，NH-EPL was applied in Xinjiang and Jiangsu area on site. The results showed that NH-EPL had excellent extreme pressure friction resistance and lubrication performance. At room temperature，the lubrication factor reduced 93.4% and the wear loss reduced 99.87% by 0.5% NH-EPL. The pressure capacity of NH-EPL was 320 kgf. NH-EPL had good resistance to temperature（160℃）and salt. The lubrication factor of 20% NaCl salt water slurry reduced 80.43% by NH-EPL. The foam ability of NH-EPL was poor and the foaming rate of base slurry containing 0.5% NH-EPL was only 1.0%. The fluorescence level of NH-EPL was one level. It had no biological toxicity which was in accordance with environmental guidelines. NH-EPL had little effect on the rheological property and filtration property of mud，and the compatibility between NH-EPL and other treatment agent was good. The field application effect of NH-EPL was remarkable in Xinjiang and Jiangsu area with drilling friction reduction rate up to 50%，which met the demand for drilling service of deep，highly-deviated and horizontal wells.

Abstract:In order to solve the problem of wellbore instability in drilling process，the hyper-branched polyethyleneimine（HPEI）with weight average molecular weight of 6×10⁴ g/mol was selected as a shale inhibitor for water-based drilling fluid. The inhibitive performance on shale of HPEI was evaluated via bentonite inhibition texts，linear swelling experiment and shale hot aging recovery experiment. The inhibition mechanism of HPEI was analyzed by means of infrared spectroscopy，X-ray diffraction and thermogravimetric analysis. The results showed that HPEI exhibited excellent inhibitive property on the hydration expansion of shale. The yield point of suspension with 20% bentonite in 1.5% HPEI solution were only 0.5 Pa. The swelling hight of bentonite in 3% HPEI solution reduced by 67% than that in distilled water. The lower the pH value of solution，the higher the protonation degree of HPEI and the better effect of inhibition on the dispersion of bentonite were. The mechanism of HPEI inhibiting clay hydration expansion was described as follows. The HPEI molecules entered the clay layers and weakened the clay hydration through the common role of electrostatic attraction and hydrogen bonding. The hydrophobic structure of HPEI prevented water molecules from entering the clay layers and suppressed the expansion of bentonite crystal layer.

Abstract:Solid content of submicron particles in drilling fluid has a great influence on the performance of drilling fluid. It is necessary to research targeted and effective flocculant to remove submicron poor solid and minimize the flocculation of useful solid such as bentonite. Using kaoline and bentonite as flocculation objects，the flocculation effect of the long chain alkyl quaternary ammonium salt，dimethyl distearylammonium chloride（DODMAC），and the flocculation mechanism were investigated by the zeta potential，turbidity analysis，particle size analysis and potential energy calculation. The results showed that the kaoline dispersion reached the point of zero charge near the pH 5，and its surface electrical behavior and electric quantity were susceptible to pH，while that of bentonite was more stable. When the dosage of DODMAC was 42.86 mg/L，turbidity removal rate（TRR）of the kaoline dispersion was more than 90%，but it gradually decreased when the dosage was more than 42.86 mg/L. Meanwhile，the TRR of the bentonite dispersion gradually increased with increasing the dosage of DODMAC，moreover，the TRR was very low compared to that of kaoline dispersion. Therefore，the selective flocculation of kaoline could be achieved by adjusting the amount of DODMAC. DODMAC could reduce the energy barrier needed to overcome when kaoline occurred agglomeration and promote the agglomeration degree of kaoline particles through electric neutralization and hydrophobic flocculation. When the dosage of DODMAC was too large，the surface electrical behavior of kaoline particles would be reversed and the zeta potential would increase，which resulted in that the electrostatic repulsion between the kaoline particles increased and kaoline particles dispersed. As for the bentonite dispersion，DODMAC played an adsorption-bridging role in flocculation of the bentonite particles.

Abstract:In order to resolve the wellbore stability of hard-brittle shale of Nanpu oilfield with nano-micro pore throat of shale，nano-micron plugging material HSM and HGW was introduced and the recipe of the micro-nano and anti-sloughing drilling fluid，composed of 3% bentonite muds， 1.2% tackifier DSP-2， 6% filtrate reducer SPNH， 3% filtrate reducer SMP-I， 1% viscosity-reducer SMT，0.5% inhibitor AI-1，0.8% heat stabilizer Na2SO3，1% micron plugging agent FT3000，5% KCl，2% Waterproof lock agent HAR-D，2% nano plugging agent HSM and 3% submicron plugging agent HGW，was determined.Meanwhile，the filtration property，plugging property，and anti-sloughing inhibitive of the obtained drilling fluid was studied. The results showed that the addition of 2%HSM and 3%HGW could increase the membrane efficiency from 0.21 to 0.38，reduce the filter loss by more than 35%，decrease the PPT filtrate loss and initial filtration rate，and delay the pressure transmission. The drilling fluid had favorable filtration property，plugging property，and inhibitive. After being aged at the temperature of 150℃ for 16 h，the API and HTHP filter loss of the drilling fluid was 3.7 mL and 11 mL，respectively；the linear expansion ratio of the bentonite sheeting after being soaked in the drilling fluid for 24 h was only 13.29%，the rolling recovery of mudstone debris in the drilling fluid after aging for 16 h at the temperature of 150℃ was 93.3%. Field application showed that the drilling fluid could improve borehole quality with regular borehole gauge effectively，and the drilling speed was 35.29% higher than that of the adjacent wells. The multiple purposes of well stability，reservoir protection and optimized drilling was achieved.

Abstract:In order to satisfy the performance requirements of gel material used in snubbing service，the viscoelastic polymer gel plugging system was developed using acrylamide，sodium methacrylate，heat-resistant amine monomer，ammonium persulfate，polymer LAH，crosslinking agent MEN&PLE and toughening agent CAL as raw materials. The effects of initiator，simulated oil，salt and reaction temperature on gelation time of liquid and strength of gel were investigated by employing the thicken tester of high temperature and high pressure which could simulate the real environmental strata well in laboratory. The experiment results showed that the high strength gel with the intensity up to 30 N and pressure capacity about 2 MPa/8 m formed in a wide range of pH 7—13 and reaction temperature 40—130℃. Meanwhile，the gelling time and gel strength could be adjusted by changing the dosage of initiator. The viscoelastic gel had good stability and strong contamination resistance. When the dosage of simulated oil was as high as 20% or the dosage of Ca²⁺ or Mg²⁺ was 15×10⁴mg/L respectively，the gelling property of viscoelastic gel was good.

Abstract:In order to obtain the performance characteristic of low viscosity cellulose and polymer with high concentration and high molecular weight blend system，the viscoelasticity and bearing strength after curing of plugging system which was composed of partially hydrolyzed polyacrylamide（HPAM），cellulose，chromium acetate cross-linking agent and pH regulator（NaHCO₃）were investigated by using stress controlled rheometer，viscometer，scanning electron microscope and self-made gel slug pressure testing device. The results showed that the storage modulus of HPAM aqueous solution increased with increasing molecular weight. The viscoelasticity of HPAM aqueous solution could be improved significantly by the addition of crosslinking agent and cellulose with low viscosity. Both the viscosity and bearing strength of this system increased with increasing concentration of cellulose，while that decreased with increasing concentration of NaHCO₃ because the cross-linked rate was delayed by NaHCO₃. The system which was composed of 25 g/L HPAM，1500 mg/L low viscosity cellulose，100 mg/L chromium acetate crosslinker and 20 mg/L NaHCO₃ had good pumping performance and salt tolerance，and its viscosity was lower than 2 Pa·s when the pumping time was 90 min. The bearing strength of the curing system was 0.5 MPa/m at reservoir temperature（70℃），which met the requirements of plugging in sealing operation. In the L-357 well plugging construction，the injection pressure was up to 11.9 MPa，and the extrusion capacity was 6 m³. After the completion of the construction，the pressure loss test of the leakage section was 15 MPa，and the pressure in 30 min remained the same.

Abstract:In order to improve the temperature resistance of common oil well cement fluid loss additive，a new quadripolymer fluid loss additive for high temperature cement slurry was synthesized by 2-acrylamide-2-methyl propane sulfonic acid （AMPS），acrylamide（AM），acrylic acid（AA）and N-vinyl pyrrolidone（NVP）. The effect of monomer concentration，monomer ratio and initiator concentration on the performance of fluid loss additive was studied. The temperature-resistance and salt-resistance properties of fluid loss additive and the effect on the performance of cement slurry system were investigated. The results showed that the optimum synthesis condition of fluid loss additive was obtained as follows：15% monomers dosage，monomer composition：60% AMPS，20% AM，15% AA and 5% NVP，initiator，crosslinking agent（N，N-methylenebis acrylamide）and molecular weight regulator（sodium methallyl sulfonate）dosage of 1%，0.15% and 0.8% in terms of total monomer mass respectively，7 pH value，60℃ reaction temperature，4 hrs reaction time. The fluid loss additive had good temperature and salt resistance property，the temperature-resistance capacity was up to 180℃. The API water loss of cement slurry system including 3% fluid loss additive and 36% NaCl could be decreased to 46 mL. At 180℃，the API water loss of cement slurry system including 4% fluid loss additive was 48 mL，thicken time was 308 minutes and compressive strength of cement stone was 32.5 MPa. The AMPS/AM/AA/NVP quadripolymer fluid loss additive satisfied the cementing operation requirements at high temperature.

Abstract:Removing oil-based mud adhered to borehole and casing walls efficiently is crucial to develop an excellent cement bond of the interface and cementing quality. When the surfactant and salty solution contacts with the oil，the surfactant can form interfacial film and wraps the oil，resulting in that the microemulsion is formed in situ. According to that，the microemulsions were prepared with sodium 2-ethylhexyl sulfosuccinate（AOT）and iso-tridecanol polyoxyethylene ether（AE05-13）as surfactants，diesel or white oil as oil phase. Solubilization parameter and interface tension of the microemulsions were investigated and a formula of microemulsion flushing fluid was prepared: KCl salty water + 4%AOT+ 3%AEO5-13 + 6% n-butanol. The wettability alteration ability，flushing efficiency and the compatibility of microemulsion flushing fluid was evaluated. The experiment results showed that the microemulsion phase varied from Winsor I to Winsor III and then to Winsor II with the increase of salt mass concentrations. The Winsor III microemulsion possessed the optimum solubilization parameter and interfacial activity，and the optimal salinity of Winsor III dieesel microemulsion and white oil microemulsion was 7% and 10%，respectively. The density and rheological property of microemulsion flushing fluid could be adjusted and its flushing ability was good. Performances evaluation showed that the wettability alteration ability of the flushing fluid was excellent，and the flushing efficiency for oil-based drilling fluid was higher than 95% in 7 min. The compatibility of microemulsion flushing fluid with oil-based drilling fluid and cementing slurry was excellent.

Abstract:The hard brittle of traditional cement was not only causing the damage of integrity of oil well in the course of work and subsequent construction，but also the main cause of failure of inter-zonal isolation. In order to study and improve the performance of cement further and solve practical problems of well cementation，the admixtures，such as styrene-butadiene latex，silica fume and asbestos，were added to the ordinary cement（G-pure cement），which formed latex cement（a combination of G-pure cement and styrene-butadiene latex），binary compound cement（a combination of G-pure cement，styrene-butadiene latex and silica fume），and ternary compound cement（a combination of G-pure cement，styrene-butadiene latex，silica fume and asbestos）. The effect of admixtures on nine kinds of mechanical properties of those cements were investigated，including compressive strength，Young’s modulus，Poisson’s ratio and bulk modulus，etc. The results showed that four types of cement，including traditional cement，latex cement，binary compound cement，and ternary compound cement had similar Poisson’s ratio values with about 0.2. Furthermore，compared with the traditional cement，the compressive strength of latex cement and binary compound cement enhanced 24.6% and 12.3% while that of ternary compound cement reduced 11.2%，respectively. Young’s modulus and bulk modulus of elasticity of binary compound cement increased 11.8% and 12.9%，respectively，while those of latex cement decreased 2.9% and 8.2%，and those of ternary compound cement decreased 14.7% and 18.6%. Binary compound cement showed more strength. On the contrary，latex cement and ternary compound cement showed better bending property and good flexibility. In addition，latex cement showed good impact toughness，which was the best choice for well cementation.

Abstract:The currently used guar-gum based fracturing fluid had high residue content and serious damage to formation. What’s more，most powdered synthetic polymer based thickening agent had long dissolution time，which cannot meet the requirement of dissolution time of thickening agent in large-scale continuously blending of fracturing fluids. In order to solve these problem，the fracturing fluid formulated by fast dissolving hydrophobic associating polymer GAF-TP as thickening agent，nonionic surfactant GAF-2 as synergist and quaternary ammonium salt GAF-16 as clay stabilizer was prepared. The formula of fracturing fluid was optimized，and the temperature and shear resistances as well as the damage to core were evaluated. Finally，the fracturing fluid was applied on one gas well in Ordos Basin. The results showed that the solubility and viscosity increasing property of GAF-TP were better than those of guar-gum. GAF-TP had short dissolution time with 60 s under room temperature in the lab and 1—2 min at 5℃ on site. The associating fracturing fluid with formula of 0.5% GAF-TP+0.3% GAF-2+0.3% GAF-16 had better temperature and shear resistances and lower damage than those of guar-gum based one. The damage ratio of fracturing fluid to matrix permeability and that of gel breaking liquid to proppant packing formation were all lower than 10%. After successful operation of associating fracturing fluid on site，absolute flow rate（AOF）was up to 11.85 × 10⁴ m³/d and flowback ratio of fracturing fluid was 80%，showing remarkable stimulation effect.

Abstract:For the existing problems of conventional CO₂ foam fracturing fluid，such as poor compatibility with CO₂，uncontrollable cross-linking，poor temperature and shear resistance，and high residue content，a polymer-CO₂ foam fracturing fluid system was formed using a acrylamide-based copolymer（BCG-8）as thickener，composed of 0.3%—0.6% thickener BCG-8+ 0.2%—0.45% thickening synergist B-55（foaming agent）+0.2%—0.3% regulator B-14+ 1% KCl，and the rheological property，temperature and shear resistance，proppant carrying capability and gel-breaking property of the fracturing fluid was investigated. The results showed that，the system kept higher viscosity at the foam quality of 55%—75%；The viscosity of the fracturing fluid remained more than 30 mPa·s after sheared for 120 min at the shear rate of 170 s^-1 and at the temperature of 140℃，which indicated that the fracturing fluid had higher viscoelastic effect，and resulted in the fracturing fluid had better proppant carrying capacity than that HPG gel had.Moreover，the broken gel fluid had lower surface tension than 24 mN/m and the residue was as low as 0.1 mg/L. With the advantages of smoothly construction，quick effect and obvious simulation effect in the shale gas wells of Yanchang oil，the system had great significance to efficient development and reservoir protection of the unconventional reservoirs.

Abstract:Most currently used friction reducer couldn’t tolerate high salinity of water that was used to prepare slickwater. In order to obtain the friction reducer that could be prepared by high salinity water，the research of hydrophobically associating polymer friction reducer GAF-RP with salt tolerance was carried out. The solubility，friction reducing property and salt tolerance of GAF-RP were evaluated. The friction reducing property，antiswelling property and damage to cores of slickwater system which was prepared by GAF-RP，synergist GAF-2D and clay stabilizer GAF-16 were studied，and the slickwater was applied on oilfield in Jilin province. The results showed that GAF-RP had better friction reducing property and salt tolerance than polyacrylamide based friction reducer. The dissolution time of GAF-RP was short and maximum friction reduction could be 80% within 120 s. GAF-RP could tolerate salinity up to 25×10⁴ mg/L and CaCl₂ content up to 1000 mg/L. Slickwater system prepared with GAF-RP had low surface tension（27.1 mN/m），high antiswelling capacity（antiswelling rate＞80%）and low damage（<5%）to matrix permeability.Flowback fluid of the slickwater could be reused and the new system had desired friction reducing property. The friction reduction of system prepared with GAF-RP was 78.2% in the field，the flowback rate was 49.6% and daily oil output was 4.3 t，showing good production performance.

Abstract:In order to improve the suspension performance of proppant in water，improve the distribution of proppant in cracks，simplify the fracturing construction process and improve the production of fracturing measures，the double bond was introduced to the surface of conventional proppant by using silane coupling agent，then expansion resin was grafted onto the surface of proppant by aqueous graft polymerization to obtain self-suspending proppant. The effects of species and dosage of silane coupling agent，monomer ratio and concentration on the swelling performance of self-suspending proppant were studied. The results showed that under the reaction condition of 600∶71∶40∶1∶8 mass ratio of proppant，acrylamide（AM），acrylic acid（AA），N，N'-methylene bisacrylamide（MBA）and 2-acrylamido-2-methylpropanesulfonic acid（AMPS），1% silane coupling agent，1‰ initiator，20% monomer（AA，AM，AMPS，MBA），30℃ reaction temperature，the expansion ratio of synthesized suspension proppant in water was 1.5—5. The cation concentration had effect on the expansion property of self-suspending proppant. Four cations were arranged according to their influence on expansion property in following order: Mg²⁺>Ca²⁺>K⁺>Na⁺. The fracturing simulation results showed that the migration effect of self-suspending proppant was better than that of conventional proppant，and the support fracture half length was 119.2 m which was higher than that of conventional proppant by 24%.

Abstract:The history of oil reservoir waterflooding development in Shahejie formation of QK18-1 oilfield was nearly 20 years. At present，more than 75% of the oil wells were lack of injection，and the economic efficiency of oilfield was low. In order to define the mechanism of reservoir damage and establish an effective method to improve the injectivity of oilfield injection wells，the micro geological features between exploration well and development well reservoir cores were compared and the reason of injection difficulty in this oilfield was analyzed through static compatibility test，water sensitivity experiment，water quality survey，combining the photos of casting thin section and electron microscope. The results showed that the key factor of oil reservoir damage was the formation of CaCO₃ with 10—30 μm particle size as a result of the incompatibility between mixed waste water and formation water. The CaCO₃ fouling in the reservoir was a rhombohedral body with good euhedral degree. The crystal grain distributed in the pore and throat，which resulted in the decrease of reservoir physical property. The salinity of mixed waste water was low，and the re-injection led to water sensitive damage. The excess content of suspended matter in water treatment system was also an important factor which influenced the water injection effect. Aiming at the damage problem of reservoir during oilfield water flooding，precaution and suggestions were put forward to improve the water intake capacity of water injection well and ensure the balance between injection and production of oilfield.

Abstract:The effective period of molecular membrane injection technique depended on the molecular adsorption performance onto the surface of reservoir rock. In order to prolong the effective period of molecular membrane injection technique，the adsorption of some cationic compounds onto the rock surface was simulated by the method of molecular mechanics and Monte Carlo. According to the results of molecular simulation，the three quaternary ammonium of alkyl fatty amine polyoxyethylene ether（AFATQA）was designed as a new molecular film injection agent. Its adsorption energy and drag reduction effect were calculated. Then AFATQA was synthesized and the structure of synthetic product was characterized. Its comprehensive performance evaluation was carried out by laboratory experiments，and the molecular membrane composite measure was implemented in Shengli oilfield. Molecular simulation results showed that the single molecule adsorption energy increased with the increase of hydrophobic chain length or charge density. Acyl amine groups and hydroxyl could improve the single molecule adsorption energy. It simulated that AFATQA had a high adsorption energy（-155.51 kcal/mol）and a significantly drag reduction effect. The synthesized AFATQA based on the disigned model could adsorbed on the surface of rock. The Zeta potential and the contact angle increased on the surface of rock with increasing AFATQA concentration，AFATQA’s swelling rate also increased. The core flooding experiment results showed that AFATQA could effectively reduce the injection pressure. After the molecular film composite measure was applied in L37-34 well，the increasing injection effect was obvious. It showed that the water injection increased，the water injection pressure reduced，the corresponding oil production increased，water content decreased and the dynamic liquid level rose.

Abstract:Tahe fractured-vuggy reservoirs have a variety of residual oil，such as attic oil，inter-well oil，et al，after bottom water driving oil or water-flooding and replacing oil. In order to analyze the dynamic characteristics of gas injection huff and puff production and the influence of different gas injection medium on the recovery of light/heavy oil reservoir，the injecting water replace oil and injecting gas huff-and-puff was simulated with an indoor 3D physical model，which was designed based on the geological datum，the huff-and-puff effect of the three gas mediums（N₂，CO₂ and composite gas（N₂∶CO₂=1∶1））on residual oil was studied at the different viscosity of 1094.5 mPa·s and 23.6 mPa·s. The experimental results showed that the injecting gas huff-and-puff could control the bottom water and increase oil production obviously，N₂，and CO₂ could replace attic oil by the impact of gravitational differentiation，and flow around oil and inter-well oil could be carried by the impact of gas swelling. After N₂，CO₂ and composite gas huff-and-puff，the oil recovery for the heavy oil with the viscosity of 1094.5 mPa·s was enhanced by 19.59%，14.54% and 7.55%，respectively；while the oil recovery for the light oil with the viscosity of 23.6 mPa·s was enhanced by 10.87%，10.12% and 7.41%，respectively. The effect of injecting gas huff-and-puff for heavy oil was better than that for light oil under this experimental condition，and the effect of N₂、CO₂ huff-and-puff was better than that of composite gas（N₂∶CO₂=1∶1）.

Abstract:In order to research the enhanced oil recovery mechanism and influence factors of CO₂ puff and huff in horizontal well in heavy oil reservoir with bottom water，the CO₂ swell experiments was carried out and CO₂ puff and huff single well simulation model was built in view of G104-5 reservoir of M oilfield. The phase changing after CO₂ swell，and the influence of technological parameters of gas injection and reservoir parameters were studied，and the CO₂ puff and huff of 7 horizontal wells from G104-5 was conducted. It is concluded that after injected 35mol% CO₂，the viscosity of heavy oil decreased by 45% and the coefficient of cubic expansion was 1.13，and saturation pressure increased by 200% and mole fraction of C₉—C₂₂ in oil decreased by 14.4mol%. After CO₂ puff and huff in the thin bottom water reservoir，the water cut of vertical well（shoot layer from 1 to 3），which had 313.17 t cumulative incremental oil，decreased to 87%，while the water cut of the horizon well，the cumulative incremental oil being of 679.91 t，decreased to 75%，which indicted that the latter had better oil-increment and water-control effect. Among all of the effect parameters，the gas volume，reservoir thickness，oil saturation，porosity was the most important parameters；while the injection speed，formation pressure，shut time，exploit speed and permeability had little effect in CO₂ huff and puff with horizon well. In the 7 CO₂ huff and puff wells of G104-5 reservoir，G104-5P101 had the biggest porosity（45%），the maximum injected gas volume（412 t），and the most cumulative incremental oil（1412.3 t）.

Abstract:During N₂ injection process in Tahe Oilfield to enhance oil recovery，asphalt deposition may occur and cause reservoir damage problem. To solve this problem，through gas injection phase analysis test and viscosity test，the influence of N₂ injection on crude oil composition and property was analyzed，the influence of the N₂ injection on the permeability of reservoir was studied through gas injection huff and puff asphalt deposition experiment with core flow device，the degree of reservoir damage was evaluated by the index of fracture width，and the measures of reducing the deposition of asphalt were put forward. Experimental results showed that N₂ huff and puff would destroy the original balance state of crude oil，increasing heavy component content in oil，decreasing light component，thus increasing viscosity of crude oil. The asphalt precipitation degree would be influenced by gas injection rounds，crack width and well bottom hole flowing pressure. The asphalt deposition was not obvious when the bottom hole flowing pressure was higher than the saturation pressure，while there were more asphalt depositions when that was lower than saturation pressure. It was suggested that the reasonable production differential pressure should be maintained to prevent the asphalt deposition in the field of gas injection production，and suitable chemical plugging agent could effectively relieve the asphalt precipitation. During N2 injection process in Tahe Oilfield to enhance oil recovery，asphalt deposition may occur and cause reservoir damage problem. To solve this problem，through gas injection phase analysis test and viscosity test，the influence of N2 injection on crude oil composition and property was analyzed，the influence of the N2 injection on the permeability of reservoir was studied through gas injection huff and puff asphalt deposition experiment with core flow device，the degree of reservoir damage was evaluated by the index of fracture width，and the measures of reducing the deposition of asphalt were put forward. Experimental results showed that N2 huff and puff would destroy the original balance state of crude oil，increasing heavy component content in oil，decreasing light component，thus increasing viscosity of crude oil. The asphalt precipitation degree would be influenced by gas injection rounds，crack width and well bottom hole flowing pressure. The asphalt deposition was not obvious when the bottom hole flowing pressure was higher than the saturation pressure，while there were more asphalt depositions when that was lower than saturation pressure. It was suggested that the reasonable production differential pressure should be maintained to prevent the asphalt deposition in the field of gas injection production，and suitable chemical plugging agent could effectively relieve the asphalt precipitation.During N2 injection process in Tahe Oilfield to enhance oil recovery，asphalt deposition may occur and cause reservoir damage problem. To solve this problem，through gas injection phase analysis test and viscosity test，the influence of N2 injection on crude oil composition and property was analyzed，the influence of the N2 injection on the permeability of reservoir was studied through gas injection huff and puff asphalt deposition experiment with core flow device，the degree of reservoir damage was evaluated by the index of fracture width，and the measures of reducing the deposition of asphalt were put forward. Experimental results showed that N2 huff and puff would destroy the original balance state of crude oil，increasing heavy component content in oil，decreasing light component，thus increasing viscosity of crude oil. The asphalt precipitation degree would be influenced by gas injection rounds，crack width and well bottom hole flowing pressure. The asphalt deposition was not obvious when the bottom hole flowing pressure was higher than the saturation pressure，while there were more asphalt depositions when that was lower than saturation pressure. It was suggested that the reasonable production differential pressure should be maintained to prevent the asphalt deposition in the field of gas injection production，and suitable chemical plugging agent could effectively relieve the asphalt precipitation.

Abstract:In order to study the effect of the hydrophobic chain length on the performance of the hydroxyl propylsulfobetaine，dodecyl（myristyl/cetyl/octadecyl）-2-hydroxy-1- propylsulfobetaine were synthesized using epichlorohydrin and primary amine（dodecyl/myristyl/cetyl/octadecyl amine）as the main raw materials and the surface tension，critical micelle concentration（c_cmc） and foam properties of the solutions were tested. The results shown that with increase of hydrophobic carbon length of hydroxyl propylsulfobetaine increased from C12 to C18，the surface tension of the solutions with the same concentration decreased，the c_cmc value decreased from 3.36 mmol/L to 1.60 mmol/L and γ_cmc value decreased from 9.6 mN/m to 25.8 mN/m，respectively. In addition，the foaming performance and synergism action with SDS of hydroxyl propylsulfobetaine improved with the increase of the hydrophobic carbon chain length.

Abstract:The reservoir of MPE3 block in Venezuela had heavy oil with high viscosity and oil layer with widely thickness and heterogeneities. In order to decrease the cost of thermal recovery and carbon emission， a novel cold production technology for heavy oil was studied in lab with homemade viscosity reducers and artificial cores under the reservoir condition of MPE3 block. The effect of profile control with gel treatment and viscosity reducer on oil displacement efficiency in the core was investigated. The results showed that the heavy oil in porous media could be split and then coated with the viscosity reducer to produce a phenomenon of granulating and viscosity reducing， which led to a higher oil recovery increment. If the core was treated with profile control before the viscosity reducer displacement， synergetic effect would happen both to increase sweeping efficiency of viscosity reducer to contact some more heavy oil and to boost the result of granulating and viscosity reducing. The higher the permeability of porous media， the easier the water channel passages were formed in drainage formation. The method of profile control including polymer gel treatment or alternative injection of N2 which applied together with the viscosity reducer displacement could enhance heavy oil recovery greatly. On the other hand， in the cold huff and puff process with gas liquid alternating injection， either stratum energy increased or formation fluid was stirred with gas-liquid， which made the viscosity reducer and heavy oil blend and formed emulsion with low viscosity easily. The oil recovery increment in the cold huff and puff process with gas liquid alternating injection could reach 16.10%OOIP.

Abstract:In order to reveal the structural cause of the interfacial activity of petroleum carboxylate and further research the combination law of petroleum carboxylate with sulfonate, three fractions of Daqing crude oil with average carbon number of 23.16, 26.01, 28.70, respectively, were selected as the raw materials to prepare a kind of petroleum carboxylate whose average carbon number is close to the carbon number of sodium oleate. The interfacial activities of sodium oleate and the petroleum carboxylate were detected and compared. Meanwhile, aiming at the Honggang oilfield with higher salinity of 11948.4 mg/L, where petroleum carboxylate could reach ultralow oil-water interfacial tension with and without weak alkaline Na₂CO₃, the effects of mixed micelles formed from petroleum carboxylate and petroleum sulfonate on interfacial activites of the combined system were investigated. The research results showed the interfacial activities of petroleum carboxylate whose average carbon number is close to the carbon number of sodium oleate, were much better than that of sodium oleate, because petroleum carboxylate was composed of molecules with different length of carbon chain and having different hydrophilic lipophilic balance (HLB) values, respectively, and having different insertion depth of molecules at oil-water interface subsequently, the distance of polar groups became far and polar group’ s repulsion reduced. As a result, their mixed micelles arranged more closely, the interfacial adsorption increased and the interfacial activity was better than that of sodium oleate which composed of identical molecules. The combination effect of petroleum carboxylate and alkyl benzene solfonate in Honggang oilfield with the higher salinity was good also. the difference of HLB value between carboxylate and sulfonate made the mixed micelles from petroleum carboxylat/petroleum sulfonate combined system arrange more closely, so that the interfacial activity of the system was better, and the time to reach the initial ultralow interfacial tension (IFT) was shorter than that of a single surfactant.

Abstract:In order to effectively deal with the oil water separation problem of surfactant/polymer（SP）binary flooding emulsion containing solid particles，the effects of diatomite，demulsifiers，partially hydrolyzed polyacrylamide（HPAM）and petroleum sulfonate surfactant on the stability of produced fluid and interfacial property of Shengli offshore crude oil SP flooding were investigated using interface tension tester and turbiscan LAB analyzer. The results showed that a compound demulsifier FP had good demulsification effect，which composed of nonionic demulsifier ECY-05 and organic silicon demulsifier 589 with mass ratio of 4∶1. The stability of the emulsion and the interfacial tension decreased and the dehydration rate increased with increasing dosage of FP. When the mass concentration of FP was 200 mg/L，the dehydration rate of crude oil emulsion with diatomite reached 88% in 60 minutes. With the increase of HPAM，surfactant and diatomite content，the stability of emulsion increased and the dehydration rate decreased. The interfacial tension between oil and water increased with the increase of diatomite，while that decreased with the increase of surfactant. HPAM had little effect on the interfacial tension. The synergistic effect of the three made the dehydration rate lower.

Abstract:In order to simulate the characteristics of Changqing ultra-low permeability reservoir and determine the reasonable exploitation method of residual oil after water flooding，oil displacement experiments were carried out by petroleum sulfonate surfactant， linear polymer and polymer/surfactant binary flooding， using three-dimensional physical model of artificial micro-fractured outcrop core and natural matrix outcrop in parallel. The experiment results showed that the physical property of three dimensional heterogeneous model was similar to that of actual reservoir，and the real situation of reservoir was simulated well.Compared with water flooding，the enhanced oil recovery rate of surfactant flooding in fracture surface，matrix layer and parallel core model was 2.65%，2.72% and 2.67%，that of polymer flooding was 5.65%，3.32% and 4.57%，and that of polymer/surfactant binary flooding was 8.23%，5.09% and 6.69%，respectively. Compared with surfactant flooding and polymer flooding，polymer/surfactant binary flooding effectively enhanced oil recovery which was expected to be used for oil displacement after water flooding in Changqing oilfield.

Abstract:In order to investigate the change regularity of components concentration and retention amount during long distance migration in compound flooding，and research the effect of alkali on components loss in flooding process，laboratory physical experiments were operated to simulate the surfactant/polymer（SP）flooding and alkali/surfactant/polymer（ASP）flooding using sand packed model with 30 meters long. During the injection of SP system and ASP system，samples were taken along the model through the sampling points，then the components concentration of the samples were analyzed. On this basis，the change regularity of chemical loss，retention and the effect of alkali on lowering the loss of surfactant and polymer were studied. The results indicated that the retention of alkali（NaOH），heavy alkylbenzene sulfonate surfactant（HABS）and partially hydrolyzed polyacrylamide （HPAM）was quite high in near inlet area（from inlet to 23.3% of whole length）during long distance migration of compound system. The chemicals’concentration reduced with the increase of migration distance，and the reduction relieved with the increase of injection volume. In comparison to SP system，alkali of ASP system could reduce the retention of HPAM by 9.69% and HABS by 9.32% from inlet to 23.3% of whole length，and escorted them into the in-depth area. Alkali had limited effectiveness on lowering components loss of polymer and surfactant under the condition of long distance migration.

Abstract:In order to study the variation law on the mobility control ability of hydrophobic associated polymer（HAP）based ASP flooding during long distance migration in porous media，a physical sand-packed model of 30 meters long with the average gas permeability of 872×10^-3μm² was set up for oil displacement experiments. The mobility control ability of HAP based ASP system was analyzed as compared with conventional ASP flooding. The results showed that the HAP based ASP system had difficulty in injection and lower mobility control ability than conventional ASP system during long distance migration. The HAP based ASP system had higher measured values of viscosity and lower pressure near inlet，which indicated that the net structure formed by association could not keep in the narrow space of pore. In second type oil layers，the minimum of the viscosity of displacement agent was 23 mPa·s for the sweep of smaller pores. The effective migration distance of ASP system was around 40% of the well spacing under experiment conditions，where the viscosity was not lower than 23 mPa ·s.

Abstract:In order to reduce the adsorption loss of ASP flooding system in near the well area and further improve the efficiency of ASP composite system，a new method of transporting ASP flooding system，combining the water jet drilling horizontal well technology with the ASP flooding，was proposed，the area， less of remaining oil near the injection wells， was drilled through using the water jet technology，and the ASP flooding system was directly transported into the area enriched of remaining oil. The physical simulation experiments were performed using the 30 cm homogeneous core with the permeability of 100×10^-3—1500×10^-3 μm²，after water flooding，the 10 cm target channel was drilled to simulate the targeted transmission of ASP compositebsystem，and thebeffect of the oil displacement of the targeted transmission of ASP composite system was studied，compared with the conventional ASP flooding. The results showed that for the core with the permeability of 100×10^-3， 700×10^-3 and 1500×10^-3 μm²，on the basis of water flooding，the enhanced of oil recovery of the 3 PV conventional ASP flooding was only 13.73%，14.76% and 19.76%， respectively，while the enhanced of oil recovery of the targeted transmission of ASP flooding system was 26.29%，29.77% and 38.84%，respectively，which was twice as much as the former. The targeted transmission technology in ASP flooding enhanced oil recovery has a very broad application prospects.

Abstract:In order to research the effect of emulsifying property of chemical flooding system on enhanced oil recovery（EOR），and reveal the relationship between emulsification comprehensive index and EOR，the oil displacement effect of polymer/surfactant/alkali（ASP）complex flooding system with different emulsion strength was studied. The results showed that it had poor effect on EOR when the emulsification comprehensive index was bigger than 70%. While the emulsification comprehensive index of flooding system was decreased to about 60% by decreasing alkali concentration and emulsification of surfactant，the enhanced oil recovery rate increased from 9.92% to 21%—30%. The best emulsification comprehensive index was about 60% for ASP flooding. The effect of decreasing surfactant’ s emulsification on EOR was bigger than that of decreasing the concentration of alkali.

Abstract:In order to study the efficiency of regional microorganisms on the degradation of crude oil，and ensure the oilfield microorganism and membrane system running smoothly of oily sewage treatment in Yanchang oilfield，six oil degradation bacteria were isolated from oil-contaminated farmland in Wuqi county of Shaanxi province. The growth and degradation characteristic of the six strains were studied through morphological observation，physiology biochemistry experiment，molecular biological techniques（16SrDNA） and GC-MS. The results showed that six oil degradating bacteria included P1 （Microbacterium oxydans），P2（Ochrobactrum intermedium）， P3 （Alcaligenesfaecalis）， P4 （Brevibacillus laterosporus）， P5 （Stenotrophomonas） and P6（Pseudomonas aeruginosa） . After cultivating and domesticating about seven days，the degradation rate of P1～P6 to crude oil was 83.47%，81.60%，85.30%，81.11%，90.58% and 93.16%，respectively. GC-MS analysis results showed that the degradation effect of strains on long carbon chain hydrocarbon was remarkable. At the same time，they all produced a certain amount of surface active substances in the process of degradation，and the maximum decline of surface tension of fermented liquid substrate was 53.19%.

Abstract:Sodium hydroxide and sulfuric acid，combined with demulsifier agent，was employed to treat the high solid content dirty oil with strong emulsification and stability. When the dosage of SP-3 demulsifier was 0.8 g/L，reaction temperature was 60℃ and reaction time was 120 min，the optimal addition amount of sodium hydroxide and sulfuric acid were achieved by orthogonal experiment，being of 40 g/L and 25 g/L，respectively，and after demulsification，the water content in oil layer could be decreased to 10.6%，realizing three-phase（oil，water and solid）separation. From the analytical data，including the content of oil，water and solid in oil layer，dirty oil component，surface tension and viscosity of oil layer，the effect of sodium hydroxide and sulfuric acid on dirty oil demulsification was investigated systematically. Therein，sodium hydroxide + sulfuric acid pretreatment could reduce the content of resin and asphaltene in dirty oil，destroy the net structure formed by solid，resin and asphaltene，make the solid particle separate from oil phase easily，and promote the coalescence of oil droplet and water droplet，respectively. Meanwhile，sodium hydroxide + sulfuric acid pretreatment could decrease the absolute value of Zeta potential obviously，thus lowering the intensity of interfacial film. Furthermore，sodium hydroxide + sulfuric acid + demulsifier could lower contact angle of water on the surface of solid particles in the dirty oil from 95.6° to 87.0°，enhancing the surface wettability of solid particle significantly. Sodium hydroxide + sulfuric acid pretreatment could decrease the viscosity，surface tension and stability of dirty oil. In general，the sodium hydroxide + sulfuric acid pretreatment combined with demulsifier agent can realize demulsification，dehydration and solid removal of the high solid content dirty oil effectively.

Abstract:To explore the high efficiency catalyst of Fenton system under the condition of high pH，Fe²⁺，Fe³⁺ Co²⁺，Ni²⁺，Cu²⁺ and Zn²⁺ salts was selected to react with 1， 10-phenanthroline to prepare the corresponding metal complexes by mixing the 0.2 mol/L two components with the same volume，and then the catalytic activity of the complexes catalyzing H₂O₂ oxidative to degrade hydroxypropyl guar gum under high pH conditions was evaluated. The results showed that the six complexes all had certain catalytic effect of H₂O₂，and CuL was the best one，which performed good catalytic effect in the range of pH 7.0—14.0. Under the condition of 45℃，pH=10.0，with H₂O₂ amount of 10.0% to the mass of hydroxypropyl guar gum，and Fe（Ⅱ） L amount of 5.0% to the mass of H₂O₂，and degrading for 40 min，the relative viscosity of the hydroxypropyl guar gum system reduced from 14 to 1.2，close to the water’ s viscosity；the relative molecular weight was reduced from 2 million to 2864；the COD value was reduced from 22.49 g/L to 8.73 g/L. Increasing the amount of H₂O₂ to 25.0% of the mass of hydroxypropyl guar gum，the COD values could be reduced to 41 mg/L within 4 hours

Abstract:In order to obtain the adsorption of different fracturing fluid thichener in formation，the content determination and adsorption capacity of three kinds of fracturing fluids thickeners（guar gum，synthetic emulsion polymer and surfactant）which were often used in oilfield were studied. The standard curve of guar gum，synthetic emulsion polymer and surfactant in fracturing fluid was established by anthrone-sulfuric acid colorimetry，starch-cadmium iodide method and reinecke salt colorimetry， respectively. The adsorption properties of three kinds of fracturing fluids thickeners in reservoir were quantitatively demonstrated by measuring the adsorption capacity of thickeners on quartz sand. The results showed that the standard curve of three kinds of fracturing fluids thickeners indicated a good linear relationship with R²>0.99. Three fracturing fluids thickeners were arranged according to their adsorption capacity on quartz sand in following order: guar gum>surfactant>synthetic emulsion polymer. Their adsorption capacity on quartz sand was 8.5，7.1 and 2.0 mg/g，respectively. Compared with traditional guar gum，synthetic emulsion polymer and surfactant could effectively reduce the adsorption of fracturing fluid in reservoir，thus reduce the formation damage.

Abstract:High performance liquid chromatography（HPLC）was the most simple and sensitive detection method of polymer concentration，however，HPLC can only test the total polymer concentration. In a practical application，the preformed particle gel （PPG）and partially hydrolyzed polyacrylamide（HPAM）are often used together in order to improve oil-displacement efficiency. To achieve the detection of PPG in produced liquid of oilfield（containing HPAM）using HPLC method，a new sample preparation method was put forward based on the structural differences between HPAM and PPG，the crosslinking agent and gel breaker was added into the sample， respectively，HPAM would be precipitated off，while PPG would still in the sample，resulting in that HPAM would not interfere with the detection of PPG using HPLC method. The experiment results showed that at first，Al（NO₃）₃ was added into the sample at the mass ratio of the Al（NO₃）₃ to the total polymer of 10∶1；after about 3 min，H₂O₂ was added into the sample at the mass ratio of H₂O₂ to the total polymer of 150∶1，as a result，the complete precipitation of HPAM achieved and the PPG could be detected alone using HPLC method. This method had good precision and standard addition recovery rate，the broad linear range was 10—200 mg/L，and the lowest limit of detection was 5 mg/L.

Abstract:The requirement of drilling operations on the anti-collapse and bonding reinforced wall performance of drilling fluid was increasing as the drilling formation conditions became increasingly complex. Plugging anti-sloughing drilling fluid additives could plug the primary pore throat and micro cracks in the formation，block the water channel，improve the sealing performance of drilling fluid，prevent free water intrusion into formation，reduce the collapse pressure of the formation and strengthen the wall. Asphalt drilling fluid additive，silicate agent，polyglycol agent and other conventional plugging and anti- sloughing drilling fluid additives were briefly introduced in this article. The recent research and application at home and abroad of aluminium-based anti-sloughing drilling fluid additive，nano anti-sloughing drilling fluid additive and biomimetic wellbore strengthener were mainly described. The development suggestions of anti-sloughing agents were also proposed.

Abstract:The size of gas flow ratio in drive process directly affected the sweep efficiency of sweeping phase and oil recovery. The special methods，which could control mobility in the process of gas flooding，included the thickening and tackifying supercritical CO₂ system，gas-soluble surfactant，emulsion of supercritical CO₂，water-gas dispersion system and micro-foam（bubble） . The control mechanism and research progress of the five methods were introduced，and the characteristic of each method was analyzed. The related research direction and application prospects were discussed，which might provide reference for the related research of mobility control of gas flooding.

Abstract:In order to promote the development of technology for heavy oil recovery by aquathermolysis，from aspects of mechanism，preparation，modification performance evaluation and so on，the advanced developments of metal nano-particle catalysts for aquathermolysis of heavy crude oil，including Ni，Mo and Fe based metal nano-particles，and the surface modification of metal nano-particles catalysts were further reviewed. In addition，the research suggestions and prospects of studies and applications of metal nano-particles catalysts for aquathermolysis of heavy crude oil were put forward