Abstract:The southern margin of Junggar Basin was characterized by a large contain of gypsum mudstone and mudstone which had a high dispersion and expansibility. Its high formation pressure required the use of high density drilling fluid with a narrow drilling fluid equivalent density window which was favorable to sticking and well leakage. In this investigation，a high density leak proof oil based drilling fluid was obtained by optimizing various ingredients as well as composite leak proof agents. The temperature，electrolytes and drilling cuttings tolerance of oil based drilling fluid was assessed and the sealing performance of formulated leak proof oil based drilling fluid was studied. The results showed that the formulated oil based drilling fluid had good temperature resistance and salt tolerance. Under the condition of 180℃ and 2.5 g/cm³ density，the rheology and emulsifying capacity of drilling fluid were stable. The emulsion-breaking voltage was bigger than 1000 V. Additionally，its rheological property and emulsifying capacity were not affected when exposed to 15% CaSO₄，12% NaCl，20% CaCl₂ and 10% drilling cuttings. When a composite plugging agent，including 1% bitumen FD-F，1% calcium carbonate（600 meshes）and 0.5% graphite powder，and 3% oil-soluble leak proof plugging agent（LCM）as the components of oil based drilling fluid，it had good plugging and leak proof performances.The sealing pressure of high density leak proof oil based drilling fluid was 7.75 MPa and the leak proof pressure at a width of 1—5 mm was 7.0 MPa.

Abstract:In order to reduce the treatment cost of waste drilling fluid，alleviate the adverse effect of waste drilling fluid on environment，and meet the requirements of drilling engineering and environment，the synthetic ester lubricant HCZ was prepared with long chain fatty acid and polyhydric alcohol as raw materials. The lubrication effect of HCZ，temperature resistance and salt tolerance，toxicity and compatibility with drilling fluid were studied. And HCZ was applied on site in Gaoshiti-grinding creek region of Sichuan province. The results showed that the lubrication effect of HCZ was better than that of polyether，asphalt and mineral oil lubricant. The adhesion coefficient decline of mud cake in drilling fluid containing 0.3% HCZ reached 51%. HCZ could improve the temperature resistance and salt tolerance of drilling fluid. HCZ had low biotoxicity，and good compatibility with polymer，organic salt and polysulfonate drilling fluid systems. The lubrication effect of HCZ was stable. The mud-cake adhesion coefficient decline of polysulfonate drilling fluid with high density containing HCZ was 49.1% after being recycled for 8 days，which met the requirement of site drilling.

Abstract:In order to obtain starch filtrate reducer with good temperature resistance，a composite modified starch filtrate reducer（CCMS）was prepared by using corn starch as raw material，chloroacetic acid as carboxymethylation agent and epichlorohydrin as cross-linking agent. The structure of CCMS was characterized by infrared spectrometry，and the filtration reduction property，temperature resistance and salt tolerance of CCMS were studied. The results showed that CCMS had excellent filtration reduction property. The API filtration loss of base slurry decreased with increasing concentration of CCMS，and that increased with increasing salt dosage in base slurry. When the dosage of CCMS was 1.5%，the API filtration loss of freshwater-base slurry，4% salt water base slurry and saturated brine base slurry was 6.8，7.8 and 8.6 mL respectively. CCMS had good temperature resistance at 160℃. In freshwater-base slurry containing 40% CaCl₂，CCMS still had good filtration reduction property，and the API filtration loss of base slurry was 9.1 mL. CCMS could obviously increase the temperature resistance as well as high-temperature and high-pressure filtration reduction property of PLUS/KCl drilling fluid，which had similar characteristics with the same products abroad.

Abstract:In order to improve the zone islation quality of cement-sheath，the ESEM，Zeta potential analyzer，FTIR measurements and the method of filter-cake simulation were applied to study the influence of drilling fluid and its filter-cake on the second interface cementation in primary cementing，and a cleaning technique of low strength filter-cake（LSFC）was proposed. The results showed that the properties of drilling fluid，used during drilling operation，was not satisfied to improve quality of second interface，the drilling fluid was easy to form LSFC on the wellbore，which will decrease the shear strength of second interface between cement sheath and formation，and the shear strength between cement stone and core was only 0.12 MPa after curing for 7 days. A cleaning technique of LSFC was presented to improve the shear strength，including the improvement of the pH value of drilling fluid to damage chemical structure and to increase the hydrophily of drilling fluid additives，and the ζ potential of particles in drilling fluid increased to increase the dispersion between particles.When Controlling the properties of drilling fluids to make the pH≈11，the flow behaviour index n＞0.75 and yield point YP≈5 Pa，the shear strength between cement stone and core could be increased from 0.12 MPa to 1.18 MPa. The technique combining with the suitable slurry column structure，had been successfully applied on 14 wells in Dagang oilfield. The cementing quality of second interface between cement sheath and formation was substantially improved，the average high-quality increased from 23.1% to 71.6%.

Abstract:In order to further study the corrosion mechanism of acidizing corrosion inhibitor，the relationship between molecular structure and inhibition efficiency of corrosion inhibitor was analyzed by combining experimental method with quantum chemistry and molecular dynamics. The inhibition efficiency of five acidizing corrosion inhibitors in 15% HCl solution was measured by weight loss method，such as glycine，N-［N-［（phenylmethoxy）carbonyl］glycyl］-，4-nitrophenyl ester（A），Nα，ω-dicarbobenzoxy-L-arginine （B），N-（2-benzoylphenyl）-1-benzylpyrrolidine-2-carboxamide（C），ethyl（E）-3-（4-（（（E）-4-methoxybenzylidene）amino）phenyl） acrylate（D），2-amino-3-（5-hydroxy-1H-indol-3-yl propanoic acid（E）. And the 3D morphology of N80 steel after corrosion was observed by metallographic microscope. Finally，the corrosion inhibition performance of five corrosion inhibitors was analyzed by the combination of quantum mechanics and molecular dynamics. The results showed that the inhibition efficiency of five acidizing corrosion inhibitors was above 93%. The inhibition effects of five acidizing corrosion inhibitors were arranged according to the order of inhibition efficiency in following order：B>A>D>C>E，according to average pitting depth in following order：B>A>D>C>E，and according to maximum pitting depth in following order：A>B>D>C>E. B and D corrosion inhibitor had poor inhibitory effect of pitting corrosion. The corrosion inhibition performances of five corrosion inhibitors were arranged according to the calculated results by quantum chemistry in following order：A>B>D>C>E，and according to the calculated results by molecular mechanics in following order：A>B>C>D>E，which agreed with the experimental results.

Abstract:In order to improve the temperature resistance of guar gum fracturing fluid and adapt to the development of complex special reservoirs such as deep layer，a nano-silica hybridized fracturing fluid was developed by using nano-silica and guar gum，and the gel was prepared by adding sodium tetraborate crosslinker to fracturing fluid. The effect of mass fraction of nano-silica and crosslinking ratio on the apparent viscosity of gel was studied，and the temperature resistance，viscoelasticity and mechanical property of fracturing fluid gel were investigated. The results showed that it had a big influence of mass fraction of nano-silica and crosslinking ratio on the apparent viscosity of fracturing fluid gel. The nano-silica hybridized fracturing fluid gel which contained 0.3% guar gum，3000 mg/L nano-silica and 0.2∶100 crosslinking ratio（mass ratio of sodium tetraborate to base fluid）showed good temperature and shear resistance. It’s viscosity was 150 mPa·s after shearing 60 min at 170 s^-1 and 90℃，which increased 60 mPa·s comparing with pristine guar gum. The network structure of guar gum fracturing fluid gel was enhanced by nano-silica owe to the good dispersion，increased elasticity and tensile strength of fracturing fluid. Compared with that of pristine guar gum，the elastic modulus of nano-silica hybridized fracturing fluid increased 45% and the tensile force increased 4 N under 10 mm deformation.Nano-silica hybridized fracturing fluid could be used in the fracturing development of complex reservoirs.

Abstract:In order to obtain one type of clear fracturing fluid that could be used for low-medium temperature reservoirs，VES-LT fracturing fluid was prepared by using binary cationic viscoelastic surfactant VES-LT as main agent，sodium salicylate as micelle co-agent and potassium chloride as clay stabilizer. The rheological behaviors，proppant-suspension property，breaking property and the effect on permeability of proppant pack layer were evaluated. The results showed that the viscosity of fracturing fluid increased with increasing concentration of VES-LT. The VES-LT clean fracturing fluid had good resistance of high temperature（110℃）. The effect of temperature on the viscosity of VES-LT clear fracturing fluid was smaller than that of cross-linked guar gum fracturing fluid. The static proppant-suspension property of VES-LT clear fracturing fluid was much better than that of conventional guar gum fracturing fluid with similar viscosity when the proppant concentration was 20%. This clean VES-LT fracturing fluid system didn’t need gel breaker. Both oil and water could break the gel down and the viscosity of broken fluid was 2.4 mPa·s. The damage of VES-LT clear fracturing fluid to the permeability of proppant pack layer was far less than that of conventional guar gum fracturing fluid system. This clear VES-LT fracturing fluid system could be used for low-medium temperature stimulation of low permeability unconventional reservoirs.

Abstract:In order to obtain the thickening agent used in fracturing fluid on the condition of ultra-high salinity and 210℃ high temperature，a terpolymer thickening agent APC-30 was prepared by acrylamide（AM），2-acrylamido-2-methylpropanesulfonic acid（AMPS）and acryloyl morpholine（ACMO）. The viscosifying performance，salt-tolerance and thermal stability of APC-30 were investigated. Furthermore，the temperature and shear resistance，viscoelasticity and breaking property of the gel fracturing fluid with the combination of APC-30 and organic zirconium crosslinking agent BPA were studied. The results showed that APC-30 which synthesized on the condition of 70∶24∶6 monomer mass ratio of AM/AMPS/ACMO，0.4% composite initiator K₂S₂O₇-NaHSO₃ and 1.2% chain transfer agent HCOONa presented a better viscosifying performance，thermal stability and salt resistance than binary polymer thickening agent AP-30. The viscosity retention of APC-30 was 35% under the condition of 450 g/L salinity，200℃ temperature and 170 s^-1 shear rate. The introduction of morpholine group with six-membered heterocyclic structure could obviously improve the temperature and shear resistance of fracturing fluid gel. The viscosity of APC-30 fracturing fluid gel was 175.8 mPa·s after shearing at 210℃ and 170 s^-1 for 2 hrs. The APC-30 fracturing fluid gel had the characteristics of high elasticity，low viscosity as well as excellent sand carrying capacity. The broken liquid of fracturing fluid had low residue content and easily backflow. The new type fracturing fluid could be used for fracturing operation on site.

Abstract:In order to improve the rheological and drag reduction properties of xanthan gum（XG），carboxymethyl xanthan gum（CMXG） was synthesized by XG and etherifying agent （sodium chloroacetate）. The rheological properties （shear thinning，viscoelasticity and thixotropy），temperature and shear resistance and drag reduction property of CMXG solution were studied. The results showed that the viscosity of CMXG increased significantly comparing with XG. The viscosity of 6 g/L CMXG solution was 1.56 times more than that of 6 g/L XG solution. The storage modulus，loss modulus，thixotropy and temperature resistance of CMXG solution were greater than those of XG solution. XG and CMXG solutions had shear thinning properties，and the change curve of viscosity with shear rate could be characterized by Cross model. The drag reduction rate of CMXG solution in smooth tube increased with increasing concentration and flow rate. The maximum drag reduction rate of 1 g/L CMXG solution reached 64.3%，and the drag reduction effect was better than that of XG.

Abstract:The pressure slope calculation of CO₂ foam fracturing fluid in conduit flow was the key to reliability of whole fracturing process，which influenced the effect of formation stimulation. The friction characteristic of CO₂ foam fracturing fluid was investigated at high temperature and pressure by conduit flow experiment which simulated field condition，and the effect of pressure，temperature，foam quality，and flow rate on friction characteristic of CO₂ foam fracturing fluid was analyzed. The mathematic model of friction resistance coefficient was established，and the friction resistance of CO₂ foam fracturing fluid in turbulent flow was predicted. The results showed that the friction resistance coefficient of CO₂ foam fracturing fluid declined with increasing temperature，flow rate and pressure，and increased with increasing foam quality. Once the foam quality exceeded 75%，the friction resistance coefficient would reduce. The effect of pressure on the friction resistance coefficient was not obvious. The calculating result of mathematic model of friction resistance coefficient indicated that CO₂ foam fracturing fluid had viscosity increasing effect on the condition of laminar flow，and that had friction reducing effect on the condition of turbulent flow. On the condition of same delivery rate，the friction resistance of 31/2″ tube was less than that of 27/8″ tube，and 31/2″ tube was usually applied for CO₂ foam fracturing. The investigation on friction characteristic of CO₂ foam fracturing fluid was helpful to design parameters of field fracturing.

Abstract:In order to improve the heat resistance and lower the cost of clean fracturing fluid，a Gemini cationic surfactant GX22 was synthesized by long carbon chain alkyl amide propyl dimethylamine，epoxy chloropropane and hydrochloric acid. The heat resistance and rheology of clean fracturing fluid consisting of GX22 were investigated. The results showed that GX22 could form micelle system in aqueous solution without salt. The clean fracturing system was characterized by significant shear thinning property，and the flow curve of system could be described by Cross constitutive equation model. The thixotropy enhanced withincreasing GX22 concentration，which meant the structural strength was stronger. The elastic modulus G' and viscous modulus G'' both increased when angular frequency increased，and G' was always greater than G''，which indicated that the elastic modulus of fluids was predominant. The viscosity of clean fracturing fluid with 3% GX22 was 33.53 mPa·s after shearing for 90 minutes at 110℃ and 170 s^-1，showing good temperature resistance. Compared with the same type of clean fracturing fluid，the clean fracturing fluid with GX22 had such features as simple synthetic process，available raw materials and without product reprocess of GX22，easy preparation and low cost of fracturing fluid.

Abstract:There were some problems in mid-deep water-flooding reservoir of Jidong oilfield，such as injection water forward one-way，big difference of water injection profile，and the difficulty of injection production adjustment. So silicate gel plugging agent was developed using silicate，water retention agent and activator. The gelling principle of silicate gel plugging agent was analyzed，the injectivity and plugging performance were studied，and the field application was carried out in Jidong oilfield. The results showed that when the mass ratio of silicate，water retention agent and activator was 5∶1∶0.2，the plugging rate of plugging agent to media and low permeability sand pipes was 93.5% and 97.3% respectively，showing good injectivity and plugging ability.The plugging agent had good injection selectivity which preferred to plug higher permeability layer. The diversion rate of low permeability sand pipe increased from 29.8% to 85.2% and that of high permeability sand pipe decreased from 70.2% to 14.8%. The gel strength was improved by the cross-linked network structure coated with silicate gel and silicate precipitate. After the silicate gel plugging agent was applied in 6 wells on site，the average water injection pressure increased 4.67 MPa，the water injection profile was improved and water injection volume was increased. There were 8 corresponding wells which had an obvious effect of increasing oil production and decreasing water cut and the cumulative oil increment was 4314 t.

Abstract:Alkali lignin plugging agent had excellent resistance to temperature and salt，but it had many shortcomings，such as bad toughness，easy to break and short period of validity. In order to improve the toughness of system，the toughening agent was added to conventional alkali lignin plugging agent. The effects of component dosage，including alkali lignin，crosslinking agent and toughening agent，pH value，temperature，salinity and reaction time on the gelling property were studied. The toughness of gel system was evaluated by means of elastic modulus test and infrared characterization. The actual plugging effect was obtained by plugging test with sand filled tube. The results showed that the optimum formula of alkali lignin high temperature gel was obtained as follows：6.0% alkali lignin，5.0% crosslinking agent and 0.5% toughening agent，whose gelation strength was 0.048 MPa and the gelation time was 8 h at 120℃. The gelling pH value of alkali lignin plugging agent system was 7—11，the salt tolerance of that reached to 20 × 10⁴ mg/L，and the temperature resistance of that was 140℃ . The elasticity of gel system was greater than the viscosity，and the elastic modulus of gel increased with increasing concentration of toughening agent. The plugging ability and abrasion resistance of gel plugging agent were good whose plugging rate was above 97%. It could meet the demand of profile control and water shutoff operation in fracture-cavity reservoir with high temperature and high salinity.

Abstract:In view of the unsatisfactory chemical sand control effect caused by oil film and water film on the surface of sand in the well of Shengli oilfield，a kind of active sand consolidation agent was prepared by using epoxy resin as main chain and linking hydrophilic and lipophilic groups to side chain which based on the graft reaction mechanism of free radical. The structure of active sand consolidation agent and the stability of sand consolidation agent emulsion were studied by infrared spectroscopy，elemental analysis，thermogravimetric analysis and dynamic light scattering. Meanwhile，the effects of curing temperature，curing time，crude oil content and water content of sand filling tube on the compressive strength and permeability of consolidated core were investigated. The experimental results showed that the active sand consolidation agent with hydrophilic and lipophilic groups had good emulsion stability and low viscosity. The thermal decomposition temperature of sand consolidation agent was 80℃ which was suitable for low temperature underground environment. The effects of curing temperature，curing time and water content of sand filling tube on the compressive strength of consolidated core were great. The compressive strength of consolidated core increased with increasing curing time，and that increased first and then decreased with increasing temperature. With the increase of water content in sand filling tube，the compressive strength of consolidated core increased first and then decreased，and the permeability decreased gradually. With increasing content of crude oil in oil-water mixture，the compressive strength of consolidated core decreased，but the degree of reduction was small，indicating less influence by the content of crude oil. The compressive strength and permeability of consolidated core prepared under the condition of 40—80℃ water bath，20% crude oil content and 72 h curing time were 5.5 MPa and 17.5 μm² respectively，which almost were not affected by oil and water films on the surface of sand.

Abstract:Due to the low permeability and high capillary resistance，the development of oilfield by water injection is very difficult and the spread of water flooding is limited for low/ultra-low permeability reservoir. The potential of a further substantial increase in oil recovery is displacing the remaining oil in the low permeability area by water flooding. Based on the self-made nano SiO₂ colloidal silica，lipophilic，hydrophilic and hydrophobic modified nano SiO₂ chemical samples containing long chain alkyl，hydroxy，short chain alkyl group，respectively，was prepared and the basic structure was characterized by dynamic light scattering and IR. The injection ability of these samples was evaluated by capillary analysis system and the mechanism was further studied on the basis of experimental analysis. The results showed that the modified nano-meter SiO₂ had the ability of greatly improving the injection capacity of low permeability area compared to that of the surfactant OP-10，which was little affected by the size of the nano-meter SiO₂. Moreover，the hydrophilic modified nano SiO₂ had the best effect of improving the injection capacity compared to that of the lipophilic and hydrophobic modified nano SiO₂. The water clusters structure was formed by the hydrogen bonding between water molecules. The dynamic combination between each water cluster maybe the important reason of the difficult water injection for low/ultra-low permeability reservoir. The nano particles in colloidal silica did the Brownian movement constantly. The motion of water molecules and the hydrogen bond network rearrangement was changed，so as to realize the change of the structure of water molecule clusters，and thus increased the water injection ability to further expand the water sweep volume.

Abstract:CO₂ could react with formation water and reservoir rock when it was injected into reservoir. The interaction of CO₂-rock-water could change the porosity，permeability and pore structure characters of the reservoir. In this paper，the changes of porosity，permeability and pore structure of the rock were measured after rock reacted with CO₂ and water in different reaction times and under different reaction pressures. The apparent morphology of the rock and Ca²⁺ concentration in water after the interaction of CO₂-rock-water under different pressures were also measured. The results showed that the change in pore structure of rock was influenced by the comprehensive effects of dissolution，particle migration and the deposition of new minerals. With the change of reaction time and reaction pressure，the distribution of small pores in rock changed greatly，while that of macropores changed little.The water permeability of rocks all decreased after CO₂-water-rock reaction of 6—24 hrs. With the increase of reaction time，the porosity of rock decreased first and then increased，the permeability recovery of rock increased gradually which showed that the effect of CO₂ on reservoir permeability changes decreased gradually. The water permeability of rocks all decreased after CO₂-water-rock reaction under 7—15 MPa. With the increase of reaction pressure，the porosity of rock increased first and then decreased，the permeability recovery of rock decreased gradually which showed that the effect of CO₂ on reservoir permeability changes increased gradually. The dissolution of rock was more obvious and the concentration of Ca²⁺ in solution increased with the increase of reaction pressure.

Abstract:According to the characteristic of the higher Ca2+，Mg2+concentration in formation water and more acid sensibility mineral in reservoir rock of CO₂ flooding in Yanchang formation，the corrosion and precipitation simulation experiments of CO₂，formation water and rock mineral system in the different parts of reservoir was carried out. The results showed that the dissolution quantity of CO₂ increasesd gradually and pH value increased in formation water，precipitation wouldn’t happen due to pressure decreased in CaCl2-type formation water and corrosion reaction would happen between CO₂-water solution-reservoir mineral in the near-wellbore area of CO₂ injection well and deep area of reservoir. The dissolved CO₂ would escape form formation water largely，and the carbonated inorganic scale would generate in CaCl₂-type formation water and some mineral that dissolved in formation water would separate out largely due to the pressure decreases quickly in the near-wellbore area of production well. Therefore，precipitation would not happen easily and the physical properties of reservoir would be improved in the near-wellbore area of CO₂ injection well and deep area of reservoir；but carbonated inorganic scale would be precipitated easily and caused by reservoir blockage in the near-wellbore area of production well in Yanchang formation.

Abstract:Foam draining was important for maintaining normal production of natural gas. However，the water loading in downhole was vulnerable to be contaminated by different chemicals，which made it difficult for us to design and produce highly-efficient foaming agents. In this study，a general analysis method for downhole pollutants was established based on the combination of infrared spectrometer，nuclear magnetic resonance spectrometer and liquid chromatograph mass spectrometer，et al. The main composition and corresponding content of pollutants in water loading from six gas wells in western Sichuan basin were analyzed following this method，and then the source of pollutants was discussed. The results showed that the pollutants content of each well was very different，and the main composition of pollutants was surfactants，inorganic salts and condensate oil. If the pollutants had surfactants，the foaming agents should not contain or only had a little bit of alcohols in order to avoid forming emulsion.Furthermore，using zwitterionic surfactant or nonionic surfactant as the main component of foaming agents，or using acid liquid dissolving inorganic salts could reduce the adverse impact of inorganic salts on foaming operation. In addition，using amine oxide surfactant with long-chain alkyl group as the main composition of foaming agent was beneficial for the draining of wells with high content of condensate oil.

Abstract:In process of exploring the complex fault-block reservoir with edge water， water coning problem will be more and more serious， which will lead to excessive water production and reduce the oil production. A related experimental model was developed to evaluate the effectiveness of nitrogen foam preventing edge water coning in huff-n-puff wells by comparing with that of single nitrogen system and surfactant-polymer system. The model also was used to analyze the effect factor， optimize injection parameters of nitrogen foam and study on its mechanism. The results showed that the nitrogen foam was not only combined with both advantages of nitrogen and surfactant-polymer， but also had its own superiority in preventing edge water coning in puff and huff wells， the huff-n-puff wells’oil displacement efficiency increased by 6.12%， and the water cut decreased by 21.81% after nitrogen foam stimulating. Moreover，the ability of nitrogen foam to inhibition edge water coning would gain an ideal result with heterogeneous reservoir and low viscosity oil. When the edge water was insufficient， conversed in pump’ s velocity 0.5 mL/min， the application of nitrogen foam would be more successful in controlling edge water coning as edge water force weakening. When the edge water is more adequate， conversed in pump’ s velocity 2.5 mL/min， with the volume of injecting foam selected 0.1 PV and the option of soaking time chosen 24 h， the stimulation of nitrogen foam in huff-n-puff wells would be more effective in preventing edge water and achieve more profit margin.

Abstract:As for gas channeling happened in horizontal well during multiple thermal fluids huff and puff， the properties of thermal thickening gel（TTG）， containing cellulose ether as main component， such as static and dynamic gelling temperature， rheological and viscoelastic properties， plugging performance and enhancing oil displacement efficiency were measured. The results indicated that the gel static and dynamic gelling temperature of the TTG was 65℃ and 70℃， respectively. In environment of 80℃ and 0.5 Hz frequency， the elasticity modulus and viscous modulus of TTG with mass fraction of 1.5% could reach 30—40 Pa and 2.5—7.5 Pa， respectively. When adding 0.6 PV TTG aqueous solution with mass fraction of 1.5% ， the plugging ratio of gel to hot-water and multiple thermal fluid in core permeability of 13.08 μm2 and 3.2 μm2，respectively，was 99.7% and 98.85% ，respectively. The optimized gel injection was 0.6 PV， and the displacement efficiency could be improved by 16.2%. After thermal thickening gel sealing technology was used on site， the injection pressure increased by 2.5—4.5 MPa， and the producing wells around heat injection well were not affected during thermal fluid injection period. The well average daily oil production was 40 m3， and increased by 42.8% compared with that before injection thermal thickening gel work.

Abstract:In order to study the application of core experimental data in numerical simulation， the relationship between the dynamic adsorption capacity of n-butanol and sodium dodecyl sulfate in natural cores with permeability of 10 × 10^-3—15 × 10^-3 μm²and their concentration was measured， which could provide basic dynamic adsorption parameters for numerical simulation. A micro-emulsion system was prepared with crude oil， n-butanol and sodium lauryl sulfate as main agents， and the threshold pressure gradient of microemulsion system in low permeability natural cores was determined using the differential pressure flow method， and the displacement experiment was carried out. The experimentally measured parameters were applied to the numerical simulation software CMG for small-scale numerical simulation of cores. The results showed that as for the core with the permeability of 10× 10^-3—15×10^-3μm²， the adsorption equilibrium of the sodium lauryl sulfate and n-butanol could be reached， respectively， when their mass fraction was 4% and 10%， respectively， and their dynamic adsorption capacity was 4.2 mg/g and 3.2 mg/g ， respectively. The dynamic adsorption capacity of n-butanol and sodium dodecyl sulfate measured in the core experiment could be directly used in the numerical simulation， while the experimentally measured threshold pressure gradient need to be adjusted appropriately. The adjusted simulation results was in good agreement with the actual core experiment.

Abstract:In order to obtain dodecyl dimethyl betaine（BS-12）microemulsion system with good oil displacement performance， the effect of NaCl and n-butanol dosage on the phase change of BS-12/n-butanol/n-hexane/NaCl microemulsion was studied through Winsor phase diagram method，and the influence of phase volume change on the solubilization and interfacial tension of microemulsion was also studied. The oil displacement performance of BS-12 microemulsion system prepared according to the optimum formula was evaluated. The results showed that NaCl and n-butanol had great influence on the phase state of microemulsion. The phase of microemulsion had undergone the transition from Winsor I to Winsor III and Winsor II with increasing addition of NaCl and n-butanol. The Winsor III（middle-phase）microemulsion（1 ∶1 oil-water ratio）formed by 4% BS-12， 9.3% n-butanol and 3.8% NaCl had the strongest solubilization ability， the lowest interfacial tension and the largest oil displacementpotential. The results of indoor core displacement showed that the middle-phase microemulsion could reduced water content by 9.4% on the basis of water flooding and increased recovery rate by 8.34% ， indicating good effect of enhancing oil recovery and reducing water cut.

Abstract:During the seepage of ternary compound system in reservoir，displacing capacity of the system dynamically changed due to the shear degradation of polymer and the adsorption and retention of surfactant，which affected the actual displacing ability of compound system as it reached deep reservoir. In order to determine the property variations of compound system and its effect on oilrecovery during flooding process，the effect of seepage velocity and migration distance on the viscosity of compound system and the dynamic distribution characteristic of oil/water interfacial tension along the flow direction were investigated. The influence of property variation of compound system on oil recovery was also studied. The results showed that seepage velocity and migration distance had great effect on viscosity and oil/water interfacial tension of compound system. The viscosity decreased obviously with increasing seepage velocity. When the seepage velocity was greater than 10 m/d，the viscosity decrease became inconspicuous. The shear degradation of compound system mainly occurred in inlet or near wellbore，and the increased migration distance did not cause a significant viscosity decrease after entering deep model or reservoir. The interfacial tension of compound system increased significantly with increasing migration distance. The compound system could only form ultra-low interfacial tension on the injection end or near wellbore when the injection volume was small，while it could reach ultra-low interfacial tension on deep model when 3.0 PV compound system was injected. The influence of interfacial tension variation of compound system on oil recovery was more significant than that of viscosity. And it was the key of chemical combination flooding to keep ultra-low interfacial tension as the system reached deep reservoir.

Abstract:In order to discover the influence rule of the reservoir permeability on the microbial flooding effect， the microbial growth and distribution and flooding effect in different core permeability was studied through physical simulation， and the distribution of bacteria in the cores was analyzed by scanning electron microscope. Research results showed that the maximum microbial enhanced oil recovery was 6.6% when the core permeability was of 500×10^-3μm². When the core permeability was too low（<100×10^-3 μm²），the orifice radius was smaller， the cells could not be input；at the same time， when the core permeability was too high（>1500×10^-3μm²）， the cells were output with liquid and could not realize the retention effect， in both cases the effect of microbial flooding was poor. Adsorption and retention of microbial was confirmed in the cores by the scanning electron microscope， the microorganism was advantageous to adsorption and retention when the permeability was in range of 100×10^-3—1500×10^-3 μm². The permeability rangecould be used as a basis for screening the permeability of microbial flooding reservoirs.

Abstract:In order to reduce the viscosity and improve the fluidity of viscous crude oil， the effect of the dosage of viscosity reducer consisted of alpha olefin sulfonate（AOS）and sodium carbonate（Na₂CO₃）on the viscosity reduction of viscous crude oil were studied and the mechanism of emulsification and viscosity reduction was analyzed. The results showed that the temperature resistance of AOS was good. The stability of O/W emulsion increased with increasing temperature. The effect of AOS on the emulsification and viscosity reduction of viscous crude oil was good. The viscosity of viscous crude oil emulsion decreased gradually with increasing AOS dosage. The viscosity reduction effect of viscous crude oil was the best with 81.95% viscosity reduction rate when the mass fraction of AOS was 2%. AOS and Na₂CO₃ compound system had synergistic effect on emulsification and viscosity reduction of viscous crude oil. The viscosity reduction effect of viscous crude oil after mixing with 1% Na₂CO₃ and 0.05% AOS in 1∶1 volume ratio was the best， and the viscosity reduction rate of viscous crude oil was 98.22%. Compared with the use of AOS alone， the viscosity of viscous crude oil emulsion decreased with the combination of AOS and alkali， the AOS dosage reduced and the economic benefit improved.

Abstract:In order to reveal the emulsification and demulsification of the alkali-surfactant-polymer（Na₂CO₃/KPS/HPAM， ASP） flooding in Xinjiang oilfield， the emulsification and demulsification of the ASP flooding prepared in laboratory were studied. The results showed that the Na₂CO₃had the most significant effect on the interfacial tension（IFT）between the simulated emulsion and the crude oil. When the Na₂CO₃， KPS and HPAM contents increased from 0 mg/L to 400 mg/L， the IFT decreased from 13.957 mN/m to 0.018 mN/m. The KPS had a remarkable effect on the decrease of Zeta potential， and the Zeta potential decreased from -31.5 mV to -53.6 mV when the amount of KPS increased from 0 mg/L to 600 mg/L. The HPAM had the most significant effect on the viscosity of the simulated emulsion， while Na₂CO₃ and KPS didn’ t show the function. The lower IFT， the stronger electronegativity， the higher emulsification and the higher viscosity of the water phase jointly resulted in a highly stable emulsion. In the process of demulsification， the IFT and Zeta potential of the emulsion increased sharply， moreover， the changes of the IFT and Zeta potential were positively correlated with the effect of demulsification. AR type demulsifier could produced the best of demulsification effect in treating the ASP flooding from Xinjiang oilfield

Abstract:In order to develop a multifunctional oil additive with corrosion inhibition and viscosity reduction，poly methyl acrylate-acrylic acid imidazoline（MA-ACI）was synthesized using methyl acrylate and acrylic imidazoline as raw materials， and characterized by FT-IR and gel permeation chromatography（GPC） . The corrosion inhibition property of MA-ACI was evaluated by rotating hanging plate method and electrochemical Tafel polarization curve method， and its viscosity reduction property was sdudied by rotating viscometer. The results showed that MA-ACI with the relative molecular weight 36582 could be obtained under the condition of 8∶1 molar ratio of methyl acrylate to acrylic imidazoline， 1% initiator AIBN， 80℃ reaction temperature and 10 h reaction time. MA-ACI had good corrosion inhibition effect on N80 steel sheet， and had good viscosity reducing effect on crude oil of Wei5-57 well in Jiangsu oilfield. At 30℃， the inhibition rate measuring by rotating hanging plate method was 82.06% with MA-ACI dosage of 0.10 g/L， and that measuring by electrochemical polarization curve method was 90.21% with MA-ACI dosage of 0.40 g/L. The viscosity reduction rate of crude oil of Wei5-57 well in Jiangsu oilfield was 85.28% under the condition of 100 μg/g MA-ACI and 70℃

Abstract:Two kinds of wellbore blockage is harmful to gas production in filed， including CaCO₃， CaSO₄ and BaSO₄ scales and FeCO₃， FeS corrosion products. For this problem， an acidic plug removal agent， which was composed of 10% organic acid + 1% inhibitors for the oxidation of propargyl alcohols HJF-50A + 0.5% foam UT-11C，and an alkaline chelating agent，which was composed of 10% amino acid salt YH-1 + 0.5% dodecyl sulfonate foaming agent YFP-2， was selected through investigating the scale dissolving mass， foamability and inhibition ability. The acidic plug removal agent mainly dissolved CaCO₃、 FeCO₃ and FeS. At the temperature of 20—90℃， the saturated scale dissolving rate of CaCO3 was 84.01%—87.49%， and the saturated scale dissolving mass was 67.21—69.99 g/L；the saturated scale dissolving rate of FeCO3 was 92.16%—95.98%， and the dissolving saturated scale mass was 73.73—76.78 g/L；the saturated scale dissolving rate of FeS was 64.91%—72.30 %， and the dissolving saturated scale mass was 51.93—57.84 g/L. The corrosion rate of 80S in the acidic plug removal agent was 3.13 g/ （m²·h）and the holdup rate was 90.00%. The alkaline chelating agent mainly dissolved BaSO4 and CaSO4. At the temperature of 90℃， the saturated scale dissolving rate of BaSO₄ in the alkaline chelating agent was 72.43% and the saturated scale dissolving mass was 14.49 g/L， the saturated scale dissolving rate of CaSO₄ was 76.78% and the saturated dissolving scale mass was 61.43 g/L. The holdup rate of the alkaline chelating agent was 95% . Scaling wells in filed were treated by multiple rounds of intermittent injection using the acidic plug removal agent and the alkaline chelating agent and the significant effect for dissolving scale was realized， as a result， the pressure of tubing and casing decreased from 1.01 to 3.0 MPa， and the gas production increased from 14.2% to 53.71%..

Abstract:Major changes including spiking crude oil samples and blank solutions with a known amount of stearic acid and replacing potassium hydroxide（KOH）with tetrabutyl ammonium hydroxide in titration were used to improve traditional measuring method of oil acid number，which had the defects that the oil with low acid number needed excess crude oil and did not have clear titration endpoint. The accuracy of modified titration method and national standard method was compared by testing the acid number of simulation oil and crude oil. The results showed that comparing national standard method，the modified titration method had higher accuracy，clearer titration endpoint，lower relative error and more evident peak value of first derivative differential curve，especially for the oil with low acid number and less sample amount.

Abstract:Aiming at the fact that there were few species of oil soluble tracer used in oilfield and according to the properties of organofluorine compound with stability and high sensitivity， ethyl 4-fluorobenzoate（EB-F）was synthesized by thionyl chloride method and concentrated sulfuric acid catalysis method. The structure of the product was characterized by 1H NMR and mass spectrometry. The solubility of EB-F in water and kerosene was researched through chromatographic peak area which detected by HPLC. And the detection limit of EB-F concentration by GC-MS instrument was determined by the establishment of standard curve. The results showed that the product yield of thionyl chloride method and concentrated sulfuric acid catalysis method was about 86%. Compared with thionyl chloride method， concentrated sulfuric acid catalysis method was easier to operate， had lower cost and less pollution to environment， and was more suitable for industrial production. EB-F was soluble in oil and slightly soluble in water. The solubility in kerosene and water was 90 and 0.051 g/L respectively， and the oil-water partition ratio was 338. Trace amount of EB-F acetonitrile solution could be detected by GC-MS with 0.1×10^-3—50×10^-3 mg/L linear range of standard curve， 0.9984 R²， 4.1% RSD， and 1.5×10^-6mg/L minimum detection limit

Abstract:Aiming at the problem of centrifugation that the interface boundary of residue in fracturing fluid was not clear and the clear fluid could not be pour out completely， a microfiltration filtration method was proposed to measure the residue of broken-gel fluid. The residue particle size of guar gum and polymer broken-gel fluid was analyzed by laser particle size analyzer and the pore size of microfiltration membrane was determined. The influence of sample volume，temperature and pressure on flux of microfiltration membrane was researched. Finally， the effect of centrifugation and filtration method for detecting the residue in broken-gel fluid was compared. The experiment results showed that the detection temperature of filtration method was 30℃. The suitable residue filtration condition of broken-gel fluid for guar gum fracturing fluid was obtained as follows：3 μm pore size of microfiltration membrane， 0.2—0.3 MPa operating pressure， 25 and 50 mL sample volume for guar gum and modified guar gum respectively. And that for polymer fracturing fluid was obtained as follows：0.22 μm pore size of microfiltration membrane， 0.1 MPa operating pressure，150 mL sample volume. The residue was completely separated from broken-gel fluid by microfiltration membrane filtration method whose reproducibility and accuracy were better than those of centrifugation method.

Abstract:The online monitoring of fluids flowing status in cores and visual evaluation had become important experiment method for oil displacing and enlarge sweep volume mechanism. In this paper， low field nuclear magnetic resonance and core flooding equipment were combined， and the distribution of transverse relaxtion time（T₂）was obtained based on nuclear magnetic resonance theory. Combined with mercury injection pore radius analysis results， the relationship between nuclear magnetic resonance T₂ spectrogram and pore radius of core was established using interpolation and least square method. Taking two kinds of cores with medium-high permeability（256 × 10^-3 μm²）and low permeability（7.51 × 10^-3 μm²）as an example，binding with core flooding experiments of different fluids，and using conversed nuclear magnetic pore throat distribution，the relationship between pore structure of core and the distribution of movable fluids and residual oil was obtained. The oil exploiting rate in different pore by water flooding and polymer flooding was also analyzed. The results showed that the average pore diameter of medium-high permeability core was 72 μm， the pore diameter was mainly 1—500 μm， indicating good micro-level pore development. The average pore diameter of low permeability core was 86 nm，the pore diameter was mainly 10 nm—1 μm，indicating good nano and sub-micro-level pore development. The bound water of medium-high permeability core and low permeability core was mainly concentrated in the pore space with the diameter less than 1 μm and 0.5 μm respectively. The core flooding experiments results showed that oil in pores larger than 10 μm was displaced by water， and polymer flooding showed the same tendency and oil flooding efficiency was limited. More than 80% of the residual oil was in the pores smaller than 1 μm. Improving the water flooding efficiency of low permeability zone was the key point for EOR in the future.

Abstract:Deposition of asphaltene occurs at all stages of the oil and gas production process. Asphaltene depositing in the reservoir will increase the difficulty to product oil and gas， while depositing in the wellbore will plug the wellbore which increases the difficulty of workover. At present，the asphaltene deposition was always predicted by the experimental method which was time-consuming， low efficiency and high cost. Aimed at the shortcomings of the current asphaltene deposition prediction method， based on a large number of researches， a set of asphaltene deposition prediction model and risk rating method was established by simulating wellbore temperature and pressure field and asphaltene deposition phase diagram. A single well in Bohai Oilfield was simulated. The method was quick and easy with high accuracy and no experimental study， and could be used as a quick prediction method for asphaltene deposition， which could provide suggestions for asphaltene damage prevention， judgments and release during oil field development and production.

Abstract:In order to obtain the influence of emulsion droplet size and distribution on the apparent viscosity and stability of heavy oil emulsion， the effect of temperature and shear rate on the average droplet size（referred to as droplet size）of Huanxiling heavy oil emulsion in Liaohe oilfield was investigated by using a focused beam reflectometer（FBRM） . The demulsification behavior of water-in-oil（W/O）emulsion after addition of alkaline viscosity reducer was dynamically monitored. The results showed that focused beam reflectometry enabled a good dynamic monitoring of the demulsification behavior of W/O emulsion and an assessment of the optimum amount of alkaline viscosity reducer. With increasing temperature， the droplet size of oil-water emulsion increased，and the viscosity of emulsion decreased. When the temperature was lower than 55℃ ，the droplet size of emulsion decreased with increasing shear rate， and the viscosity of emulsion decreased gradually. When the temperature was higher than 55℃， the shear rate had little effect on droplet size and viscosity of emulsion. After adding Na₂CO₃ solution to W/O emulsion，the emulsion emulsified in reverse phase， the viscosity of system reduced， the number of small size O/W emulsion droplets increased，the droplet size decreased， and the droplet distribution was more uniform. When the mass fraction of Na₂CO₃ was 0.2%， the viscosity of emulsion was the lowest， the droplet size of emulsion and the interfacial tension of oil and water reached the minimum.

Abstract:Nano-materials could improve cementing qualities and wellbore integrity through improving the strength and toughness of cement stone when they were applied in well cementing slurries. The domestic and international research progress of nano-materials applied in cementing were introduced，including nano-silica，nano-sized iron oxide，modified carbon nanotube， multiwalled carbon nanotube， nano-sized clay and other nano-materials. The existing problems and developing directions of the application of nano-materials in cementing were discussed. The discussion results had reference value for further application and research of nano-materials in the field of cementing.