Abstract:In order to improve the problems of wellbore instability and lost circulation caused by fractured strata in the southern margin of Junggar Basin，a cementing strong plugging and anti-collapse agent XZ-OSD was developed by imitating the multilayer composite structure of shell and combining the bionic strong plugging theory. The structure of XZ-OSD was characterized by SEM and IR，its thermal stability，fluid loss reduction effect and plugging property were evaluated，and the plugging mechanism was analyzed. The results showed that the spherical particle size of XZ-OSD was 50—200 nm. XZ-OSD had good thermal stability，and the decomposition temperature was 250℃. XZ-OSD had a significant fluid loss reduction effect. When only 1% XZ-OSD was added to the base slurry，the API fluid loss of oil-based drilling fluid was reduced by 72.22%，and the fluid loss at 150℃ high temperature and high pressure was reduced by 81.43%. XZ-OSD had a significant effect in protecting oil and gas formation. After 1% XZ-OSD was added to the plugging slurry，the forward plugging rate and reverse plugging rate of the core were increased by 2.89 times and 0.4 times，respectively. XZ-OSD had a good plugging effect at hightemperature. When 6% XZ-OSD was added to the plugging slurry，the fluid loss after heating at 180℃ for 16 h was only 2 mL. After entering the formation，XZ-OSD could enter pores and cracks of different sizes，plug the pores and cracks through the bridge plug and bridging. Furthermore，XZ-OSD expanded in contact with oil，the pressure-bearing capacity of leakage layer was enhanced through the expansion property and the cementing ability，thereby improving the stability of wellbore，and avoiding the occurrence of complicated down-hole accidents such as lost circulation.

Abstract:The MOF-derived plugging and inhibiting agent，rich in amine groups in outside structure，was successfully prepared，employing addition polymerization of the aziridine and the functional organic-inorganic hybrid which was prepared by zinc nitrate hexahydrate，2-methylimidazole and ethylenediamine，and it’s sealing ability，inhibition and compatibility with various drilling fluids were investigated. The agent could greatly reduce the total filtration loss of base slurry due to its excellent plugging performance. The total filtration loss of the 6% bentonite muds was 24 mL，while that of the 3% bentonite +3% agent slurry was only 4.4 mL. The yield point of the slurry system containing 2% agent was only 6.5 Pa as the bentonite reached up to 25%，and the swelling heights of the bentonite in the 2% agent system reduced by 76% compared with in fresh water system. Furtherly，the recovery rate of shale treated by the agent was satisfactory，being of 74.23%. In addition，the 3% plugging and inhibiting agent ensured the rheological property and filtration steady for drilling before and after aging and showed a slight increases in HTHP filtration as well as shale recovery rate. Based on results，the MOF-derived plugging and inhibiting agent has excellent sealing ability，inhibition and compatibility.

Abstract:A novel acid-soluble solidified plugging material was developed to solve the difficult drilling problems in control of severe losses and lost circulation in reservoir. The properties of the acid-soluble solidified plugging material，such as the density， particle size distribution，theological property，solidification performance in high temperature and high pressure，plugging efficiency and pressure bearing ability，as well as the reservoir protection performance，were characterized by conducing comprehensive experiments，and the field application scheme was proposed. Experimental results showed that the base slurry of acid-soluble solidified plugging material had a density of 1.32 g/cm3，which could be adjusted in the range of 0.8—2.47 g/cm3 by adding density regulator. The D50 and D90 of the material were 15.0 μm and 50.8 μm，respectively，which could meet the requirements of entering and plugging the fractures with micron width and above. The apparent viscosity of the base slurry was 60 mPa·s at room temperature，the final shear value was about 2—3 times of the initial shear value. The initial consistency of the slurry was less than 10 Bc，and the right-angle thickening could be realized. The thickening time of the slurry could be adjusted according to the requirement of filed operation. The slurry was highly resistant to drilling fluid contamination，when 10% volume of drilling fluid invasion，the thickening time extended by about 30 min，while the compression strength of the consolidating body changed little. The plugging material could bear pressure up to 18 MPa in fracture with 8 mm width，curing the severe losses efficiently. The permeability of the consolidating body was 0.81 × 10-3 μm2，and the consolidating body could be completely dissolved in 15% hydrochloric acid solution，which indicated that the plugging materials could protect the conductivity of fractures in reservoirs. The acid-soluble solidification material could not only effectively seal severe thief zone，but also be applied in the reservoir because of it’s removability.

Abstract:The interfacial adsorption behavior of oil and water has great influence on emulsification stability and emulsification mechanism in oil-based drilling fluid. In this paper，the dynamic interfacial tension change and interfacial viscoelasticity of oil-based drilling fluid main emulsifier PF-BIOEMUL and oil-based drilling fluid auxiliary emulsifier PF-BIOCOAT at the oil/water interface were studied by using interfacial dilatational rheology technology，and the micro-rheology of emulsion prepared by PF-BIOEMUL and PF-BIOCOAT was also studied. The results showed that the main function of PF-BIOEMUL was to provide elastic modulus and improve the strength of oil/water interface membrane，and the optimum concentration was 2.0% . The main function of PF BIOCOAT was to provide viscous modulus and reduce the interfacial tension between oil and water，and the optimum concentration was 1.5%. PF-BIOEMUL and PF-BIOCOAT could be adsorbed on the oil/water interface at the same time， which not only ensured the composite emulsifier had low oil/water interface tension，but also had better interfacial film stability， and the formed emulsion had a three-dimensional network structure. All these studies provide theoretical basis for stability research of oil-based drilling fluid system.

Abstract:In order to prepare a temperature-resistant and salt-resistant fluid loss agent for drilling fluid，polymer microsphere（PMS）was prepared with acrylamide，acrylic acid and multifunctional acrylate as the main raw materials. The linear polymer（PAAN）was synthesized with acrylamide，2-acrylamido-2-methyl-1-propanesulfonic acid and N-vinyl-2-pyrrolidone，and the polymer microsphere compound fluid loss agent （CLS） was made by the method of compounding PMS and PAAN. The performance of CLS was evaluated by thermogravimetric analysis，scanning electron microscope，Zeta potential analysis and drilling fluid performance testing. The results showed that the compound fluid loss agent CLS composed of PMS and PAAN had a synergistic effect between the components，and the fluid loss reduction performance was better than that of any single component. CLS had little effect on the rheology of drilling fluid and had excellent fluid loss reduction effect. In a drilling fluid with a bentonite content of 4%，when the dosage of CLS was 0—1%，the apparent viscosity of drilling fluid changed within ±2.0 mPa·s. When the dosage of CLS was 0.6%，the fluid loss of drilling fluid could be reduced to 6.0 mL. The initial decomposition temperature of CLS was 276℃. After the drilling fluid composed of 4% bentonite and 1.2% CLS was aged at 180℃ for 16 h，the fluid loss remained at 9.0 mL. After adding 6% NaCl，the fluid loss only changed from 5.5 mL to 7.0 mL，showing excellent temperature and salt resistance.

Abstract:In order to obtain better sealing effect，a kind of epoxy resin with special hydrophilic group was prepared in the laboratory，and the resin system was prepared by mixing the epoxy resin with the corresponding curing agent. The physical properties such as curing temperature and thermal stability of the resin system were analyzed，the effect of the resin system on the sealing ability of cement slurry was studied，and the microstructure of resin cement slurry was studied by scanning electron microscope and energy spectrum analyzer. The results showed that the curing effect of the epoxy resin mixed with the corresponding curing agent was good. The curing temperature was between 39.9℃ and 164.6℃，and the thermal stability of the cured product was good below 243.9℃. When the resin system was added into the oil well cement slurry，the sealing capacity of the cement paste could be significantly improved. Compared with the blank cement slurry，the permeability of cement paste formed by the cement slurry with 15% resin decreased from 0.037×10-3 μm2 to 0.023×10-3 μm2，decreasing by 37.8%；the cementation strength increased by 77.8% from 1.8 MPa to 3.2 MPa；the elastic modulus decreased from 9.86 GPa to 4.08 GPa，decreasing by 58.6% . The microstructure of cement paste showed that after the resin and cement slurry were solidified，the solidified products and hydration products of the resin was mixed to form a whole，and the unreacted resin polymer particles were filled in the cement paste to form a flexible structure center. The two functions jointly improve the sealing ability of cement slurry.

Abstract:In view of the high temperature of gas well in the northwest part of Gaoshi 19 well area and the unsatisfactory acidification effect caused by the high temperature and viscosity reduction of conventional self-steering acid，the self-steering acid was prepared by erucamide hydroxysulfonate amphoteric surfactant viscoelastic steering agent，corrosion inhibitor with high temperature resistance，cationic oligomer temperature inhibitor，etc. The temperature resistance，corrosion inhibition，retarding performance and self-steering performance of self-steering acid were evaluated，and then it was applied in Tiandong 110 well. The results showed that the suitable formula for self-steering acid was obtained as follows：20% HCl，8% steering agent EP-306B，2% iron ion stabilizer TYL，2% acid corrosion inhibitor GSY，1% acid corrosion inhibitor ZXJ，1% cationic oligomer DJW，6% organic acid YJS. The self-steering acid had good temperature resistance and corrosion inhibition performance. The maximum viscosity that reacted with cuttings at 150℃ was 48 mPa·s，and the corrosion rate of steel sheet was 49.8 g/（m2·h）. The retarding performance of self-steering acid was good，and the mass fraction of the acid only reduced by 3% after reacting with the cuttings for 40 minutes. The acidification of two cores with a permeability multiple of 21.4 in Gao 110 Well had a conversion rate of 72.2% for the low permeability core，indicating good self-steer performance. In the self-steering acid acidification of Tiandong 110 well，the predetermined acidification effect was achieved，and the flowback rate of residual acid reached 70%，realizing effective and uniform reservoir reformation. The self-steering acid system had a good acidification effect in heterogeneous layer of high temperature gas well.

Abstract:Research on the imbibition mechanism of gel breaking fluid of clean fracturing fluid mainly focuses on macro core wettability，oil-water interfacial tension and core-scale recovery，lacking intuitive and effective understanding of oil-water two-phase migration behavior in micro/nano pores during imbibition. In this paper，the gel breaking fluid of clean fracturing fluid was used as experimental fluid，and the dynamic distribution of oil-water two-phase under capillary force imbibition was simulated by using 2.5-dimensional pore-throat microchannel. The experimental results showed that there were continuously dynamic equilibrium processes between capillary force（driving force）of wetting phase and interfacial expansion，Jamin effect and viscous force loss（resisting force）in the imbibition process of clean fracturing fluid. The oil-water two-phase migration formed an alternate stage process of“water absorption，oil drainage and water absorption”. When the oil production efficiency reached 10.98% ， 19.09% and 37.27%，water absorption and oil drainage alternated to produce oil. It was a similar effect of“suppressing pressure”. The oil-water two-phase migration behavior in micro/nano pores was a great significance for understanding the imbibition mechanism of clean fracturing fluid.

Abstract:In order to prepare slickwater with produced water directly and simultaneously reduce its adsorption damage to reservoir， a drag-reduction agent called NY with high salt tolerance and low adsorption was synthesized by introducing polar cation fragments. Corresponding slickwater system was compounded with NY and other additives，including clean-up additive and clay stabilizer. The formula of slickwater system was optimized by evaluating its comprehensive performance. Finally，the slickwater system was applied in the shale block of Sichuan basin. The experiment results showed that NY had high salinity tolerance and drag reduction， with drag reducing rate over 70% in high salinity condition（≤300 g/L），and exhibited good compatibility with other additives. The corresponding slickwater system also showed high salinity tolerance and drag reduction. When the salinity was 0—300 g/L，the sticky time of slickwater system was shorter than 60 s，together with apparent viscosity of 1—3 mPa·s. Meanwhile，the surface tension was less than 30 mN/m，the anti-swelling rate exceeded 80% and the shale adsorption capacity was less than or equal to 3.66 mg/g，which completely satisfied the requirements of industry standard and field operation. The application of slickwater system showed that both of the success rate of fracturing operation and reuse rate of produced water were 100% in 8 wells. Compared with conventional slickwater system，this novel slickwater system had low adsorption and reservoir damage. Meanwhile，the overall liquid cost reduced by 17% and the production rate per well increased by 44%，indicating remarkable results were achieved in field application.

Abstract:In order to realize the direct preparation of slick-water with high salinity brine for volume fracturing，and to solve the high cost and environmental pollution problems of conventional W/O inverse emulsion friction reducer. An environmentally friendly salt-tolerant friction reducer PADD was prepared through introducing polar hydrophilic monomer and salt-tolerant cationic monomer into the polymer by emulsion dispersion polymerization method. The solubility，temperature resistance，resistance reduction performance and damage to the core of PADD were investigated，respectively，and the field application of PADD slick-water was mentioned. The results showed that PADD with mass fraction of 0.1% could be quickly and uniformly dispersed in clean water，40 g/L and 80 g/L mineralized water，respectively. Under the condition of high salinity（80 g/L），the molecular structure of PADD remained stable. The PADD solutions with mass fraction of 0.1% under three different salinities were aged for 72 h at 80℃，and the viscosity retention rate was greater than 90%，the drag reduction rate was above 70%，and there was less damage to the core. The high-salinity-resistant slick-water prepared with the flowback fluid using PADD as the main agent has been successfully applied in Wei 202H16.

Abstract:Aiming at the problem that the commonly used jelly fracturing fluids are difficult to resist high temperature and strong shear at the same time，a self-healing fracturing fluid（SHFF）based on dynamic covalent bonds was designed. The shear resistance， temperature and shear resistance，viscoelasticity，sand carrying capacity and gel breaking performance of the fracturing fluid were studied. The results showed that the dynamic covalent bond crosslinking SHFF could be dynamically healed under high-speed shear，and had the characteristics of dynamic reversibility，exhibiting good self-healing function. The viscosity of thickener base fluid of SHFF was low，which was beneficial to pump injection. After shearing for 3 min at 170 s-1 and then standing for 1 minutes for 3 times，the viscosity retention rate reached up to 97.6%，and the viscosity retention rate reached up to 65.7% after shearing at 170 s-1 for 2 minutes and then standing for 1 minutes followed by shearing at 510 s-1 for 2 minutes and then standing for 1 minutes for 3 times. The viscosity retention rate reached up to 99.6% when sheared at 170 s-1 for 2 h at the temperature of 120℃，which indicated that the SHFF had excellent temperature and shear resistance. In the range of 0.1—10 rad/s linear viscoelastic zone，the elastic modulus G' of the SHFF was always higher than the loss modulus G" of the SHFF. The SHFF had good sand-carrying performance，which was 75% higher than that of guar gum fracturing fluid. The residue content was nearly zero after the SHFF was broken，which indicated that the broken fluid had little damage to the formation and was easy to be flowed back. It is feasible to apply self-healing gel to fracturing fluid，and it also provides a new idea for the further research and development of fracturing fluid.

Abstract:Polymer fracturing fluid has achieved good effect of increasing oil production and lowering water cut in Daqing oilfield. In order to explore the mechanism of polymer fracturing，the evaluation experiments of oil displacement effect and filtration distance of fracturing fluid were carried out. The mechanism of polymer fracturing was analyzed from the perspective of filtration and displacement. The method of“oil displacement+fracturing”was proposed to improve the fracturing effect of oil well，and the field test was carried out in oil well of low permeability reservoir. The results showed that compared with agar solution and polymer gel solution，the polymer solution had smaller molecular aggregate size，better compatibility with core pore size，and stronger filtration capacity，which could achieve larger sweep volume and better displacement effect. Compared with polymer fracturing fluid，the displacement effect of polymer and surfactant binary system was not significantly improved，which indicated that the effect of expanding the sweep efficiency of filtration fracturing fluid was obviously stronger than that of improving the displacement efficiency. With the increase of slug size and injection differential pressure，the filtration rate of fracturing fluid increased，and the sweep volume and the oil displacement effect were enhanced. Under the same permeability and injection differential pressure，the fluid loss rate and the filtration capacity of polymer solution and slickwater solution were higher，and the filtration distance was larger under the same filtration time，but the oil displacement effect of slickwater solution was lower. The good filtration and oil displacement effect of polymer fracturing fluid were the main mechanisms to greatly improve the oil production effect of fracturing operation，which could improve the oil recovery in the matrix near both sides of the fracture. Based on the filtration and oil displacement mechanism of polymer fracturing fluid，the“oil displacement+ fracturing”（fracturing after displacing）method was proposed. Compared with conventional fracturing and“fracturing+oil displacement”（fracturing with displacing），it could achieve better oil increase effect with higher filtration loss and sweep efficiency of fracturing fluid. The method could be of great significance to further improve the oil production effect of fracturing operation for oil well.

Abstract:In order to obtain a high temperature resistant fracturing fluid thickener，hydroxypropyl guar gum（HPG）was modified with（Z）-9-octadecenoic acid amide （oleic acid amide）. The structure was characterized by FTIR，LF-NMR，TGA. the cross-linking process was fitted by 4-parameter oscillatory shear cross-linking rheological kinetic equation. Furthermore，the high temperature and shear resistance performance of the gels of O-HPG and HPG was studied. The results showed the equation could fit the process well and obtain the best cross-linking conditions. The G'max of the O-HPG gel，formed through adding 0.25% （volume ratio）zirconium organic crosslinker into 0.6% O-HPG solution at pH 10.8，was 178.8 Pa，which was three time of that of HPG gel formed at the same condition，being of 58.3 Pa；the residue viscosity of O-HPG gel was about 80 mPa·s after sheared for 1.5 hours at the temperature of 200℃ and the shear rate of 100 s-1，satisfying the demands of viscosity（more than 50 mPa·s for 60 min） for high temperature fracturing fluids. Compared with the HPG gel， the O-HPG gel had better temperature-tolerate and shear-tolerate properties，could be broken more easily. This work provides a rheological basis and a new thickener for ultra-high temperature fracturing fluids.

Abstract:Injecting plugging agent into formation is an important method to improve waterflooding effect of fractured-cave reservoir. Figuring out the velocity distribution of plugging agent is the key of construction design and effect evaluation of channel adjustment. Based on the simplified fracture model，the velocity distribution of plugging agent at different positions in the fracture of carbonate fractured-cave reservoir was deduced，the migration characteristic of plugging agent with different velocity in fracture was evaluated and the relationship between the adjustment effect and construction displacement was established. The results showed that under the displacement of field application，the velocity of plugging agent gradually decreased from 25 m/s to 0.025 m/s with the increase of flow radius from 1 m to 1/3 of well spacing（620 m）. With decreasing velocity of plugging agent，the position of accumulation was more forward and the height and density of accumulation raised. Effective accumulation could be formed when the velocity of plugging agent in formation was less than 0.25 m/s. For the typical well group of TH fractured-cave reservoir，in order to block the fractures efficiently from 100 m in the direction of main flow line，the injection rate of plugging agent should be less than 0.487 m3 /min. Based on the velocity distribution model and the migration simulation result of plugging agent in fracture， the relationship between adjustment effect and construction displacement was established，which could guide the channel adjustment work in fractured-cave reservoir.

Abstract:In order to enhance oil recovery of water flooding oilfield and extend utilization of green raw materials such as cotton staple in oil exploitation，the hydrogel plugging agent was synthesized from cotton staple through preprocessing by hydrochloric acid freezing and resolving in 6% NaOH +4% urea mixed solution，and reacting with epichlorohydrin. The performance of the hydrogel plugging agent was evaluated by thermogravimetry，static mechanical tester，rheometer and oil production chemical evaluation instrument. The optimum conditions for preprocessing cotton staple were cotton staple 3 g，dilute hydrochloric acid 36 mL with mass fraction 3%，temperature 95℃ and heating time 120 min. The synthetic conditions of hydrogel plugging agent were as follows：reaction temperature 60℃，gelling time 5 h，cotton staple 3 g，crosslinking agent of epichlorohydrin 4 mL，6% NaOH+ 4% urea mixed solution 40 mL. The prepolymer synthesized under these conditions had low viscosity，and could be pumped into oil well easily. The plugging rate of the hydrogel could achieve up to 99.64%，the compressive strength was of 131 kPa. The cotton staple hydrogel plugging agent possessed better temperature and salt resistance and low cost.

Abstract:Due to high viscosity and poor fluidity of heavy oil reservoir，it is easy to form organic scale deposition and inorganic solid phase plugging in the near well zone，reducing the permeability of the near well zone and leading to a sharp decline in formation production during the development of oilfield. According to the special reservoir physical properties and plugging types of D11 well and D34-H well in Minghuazhen formation of Bozhong oilfield，TC-4 organic plug removal agent was selected through asphalt dissolution，wax dissolution and viscosity reduction experiments，and the performance of DH-1 non-acid plug removal system was evaluated by the experiments of calcium carbonate dissolution，clay dissolution and core flow. Finally，these two plug removal systems were applied on site. The results showed that TC-4 organic plug removal agent had good dissolution ability on asphalt and paraffin，good viscosity reducing effect，and little damage to reservoir，which was suitable to remove organic plugging. DH-1 non-acid plug removal system had a good retarding speed，corrosion inhibition and scale dissolution ability，which would not cause serious damage to rock skeleton. It had good compatibility with crude oil，and broke emulsion in time during migration， which was suitable to remove inorganic solid phase plugging. After TC-4 organic plug removal agent was used in D11 well，and the combination of organic cleaning with TC-4 organic plug removal agent and DH-1 non-acid plug removal was used in D34-H well， the daily oil production，daily liquid production and the rate of water content of these two wells basically returned to the level before plugging removal. Both of the plugging removal system could solve the plugging problem in heavy oil reservoir.

Abstract:In order to study the effect of formation water salinity on the oil displacement efficiency of CO2 flooding，using Berea cores with similar porosity and permeability parameters，the core displacement method was used to test the CO2 displacement efficiency of saturated 0，6778 and 15000 mg/L water，the changes of porosity and permeability，the radius changes of pore and pore throat before and after CO2 flooding were analyzed by CT scanning. The influence mechanism of water salinity on CO2 displacement efficiency was analysed. The results showed that with the increase of the salinity of saturated water in the cores，the precipitation produced in the process of CO2 flooding increased，and the pores and throats were blocked seriously. The radius of pore and throat decreased，and the porosity and permeability decreased，resulting in the decrease of the minimum miscible pressure and the CO2 displacement efficiency. It shows that the salinity of formation water has an effect on the oil displacement efficiency of CO2 flooding.

Abstract:Based on the strategic design of intelligent nano-sized oil-displacement agent with three properties of ultra-small size， super lipophilicity and hydrophobicity，and coalescence of dispersed oil droplet，innovative idea of nano-sized water and nano-sized oil was put forward to overcome the technical bottleneck of“no injection，no production”of low-permeability reservoir. By means of modifying nano-sized particle with functional groups，the first generation of nano-sized oil-displacement agent， iNanoW1.0，was developed. Normal water could be transformed into“nano-sized water”in presence of iNanoW1.0 by weakening or destroying the association of hydrogen bonds between water molecules. Through the molecular dynamic simulation and capillary analysis，the effect of adding medium to water on the hydrogen bond by weakening or breaking between water molecules was analyzed. By conducting low field nuclear magnetic resonance displacement experiment and core displacement experiment，the injection performance and displacement effect of iNanoW1.0 and normal water were compared. The pilot test with iNanoW1.0 as oil-displacement agent was carried out in Changqing oilfield of ultra-low permeability reservoir. The results showed that iNanoW1.0 could transform normal water into nano-sized water by destroying the dynamic network structure of water molecule. Compared with normal water，iNanoW1.0 possessed better injection performance and displacement effect. With lower starting pressure gradient， iNanoW1.0 could expand the swept volume in extra-low or ultra-low permeability reservoir which could not be swept by normal water. The field pilot test in Changqing oilfield of ultra-low permeability reservoir had the characteristics of increasing fluid， increasing oil and lowering the rate of decline. The effect of enhanced oil recovery by waterflooding was observed for the first time in Changqing oilfield of ultra-low permeability reservoir. The theory of waterflooding in low-permeability reservoir was developed.

Abstract:Polymer flooding in Daqing oilfield has shifted to the type II oil layers with poorer physical properties. As the conventional partially hydrolyzed polyacrylamide（HPAM）for polymer flooding is prepared with clean water and then diluted with produced water，more polymer powders are consumed，leading to worse recovery factor. In order to reduce polymer consumption， improve the injectivity and effects of polymer flooding，a salt-resistant polymer with high molecular weight，AM/AANa/AMPSNa/ AMP（named polymer A），was synthesized with acrylamide（AM），2-acrylamido-2-methyl propanesulfonic acid（AMPS），and 1-acryloyl-4-methyl piperazine（AMP）. By optimizing the synthesis parameters，polymer A was firstly co-polymerized in water and then hydrolyzed with NaOH. General property evaluations for polymer A and HPAM with the same molecular weight were carried out. The results showed that the appropriate preparation condition of polymer A was obtained as follows：20%—21%，7.5%—10% and 0.1%—0.5% monomer dosages of AM，AMPS and AMP，0.01% initiators combination of K2S2O8-NaHSO3 and 2，2’-azobis［2- （2-imidazolin-2-yl）propane］ dihydrochloride（Va-044）dosage for total monomers in quality，0.2% chain transfer agent isopropyl alcohol dosage for total monomers in quality，2℃ initiation temperature. The salt-resistance，thermal stability，visco-elasticity and injectivity for polymer A were better than those of HPAM with the same molecular weight. The lower permeability limit for polymer A of 1000 mg/L was 112×10-3 μm2，which was lower than that of HPAM by 53×10-3 μm2. Natural core flooding experiment results showed that the enhanced recovery factor of polymer A was 4.2% higher than that of HPAM under the same consumption. Due to the better thermal stability，injectivity and higher recovery factor，polymer A was suitable for the efficient development of the type II oil layers in Daqing oilfield.

Abstract:In order to solve the problems of heterogeneity，high temperature and high salt in the oilfield exploitation，the technical idea of preparing particle oil displacement agents with small molecule crosslinking agents was broken through，and a series of particles type oil-displacing agents were synthesized with a variety of new macromolecular crosslinkers，and the network structure， mechanical properties， aging resistance and migration mechanism was studied. The research results showed that the macromolecular crosslinking agent could effectively improve the uniformity of the gel and endow the gel with excellent mechanical properties. The breaking elongation of the three gels prepared with macromolecular crosslinking agent was above 2000%，the breaking strength was above 0.3 MPa，and could be compressed to 90% without being damaged. Among them，MCH0.5-30 had the best performance，the breaking elongation could reach up to 2800%，and the breaking strength could reach up to 0.6 MPa. In addition，it had a high modulus retention rate after aging in brine with a salinity of 30 g/L at 85℃ for 90 days，showing excellent aging resistance. Macromolecular crosslinking agents provide new ideas for the preparation of high-performance oil-displacing agent，which are expected to be applied in harsh oil reservoirs with high temperature and high salinity.

Abstract:In this paper，a high-viscosity polyacrylamide molecular structure with slow-released cationic groups and delayed supramolecular thickening action was designed，the synthetic parameters were optimized，and the solution performance of temperature and salt resistance，delayed viscosification，potential and particle size，were evaluated，and the oil displacement effect of the new delayed polymer was also investigated. The results showed that the viscosity of the delayed polymer could reach up to 15.4 mPa·s at the temperature of 90℃ and at the salinity of 32864 mg/L，showing good temperature resistance and salt resistance. With the increase of aging time，the viscosity of BM solution decreased continuously，but the viscosity of the delayed polymer solution increased instead of decreasing. Moreover，the viscosity of the delayed polymer solution after aging for 90 d was 2—4 times that of conventional polymer BM solution，and the viscosity retention rate reached up to 107.7% ，showing good viscosification performance and high viscosity stability. With the prolongation of aging time，Zeta potential of the delayed viscosifier solution gradually shifted from negative to positive，and the particle size increased，which verified the delayed viscosification mechanism. The oil recovery on the basis of water flooding（recovery factor 41.2%）could be enhanced by 27.7% by injecting 0.3 PV 2000 mg/L delayed viscosifier solution. The field test also achieved a good effect of increasing oil. This technique provides a new method for reducing polymer dosage，and also provides a strong technical support for enhancing oil recovery in high temperature high brine flooding reservoir of Shengli oilfield.

Abstract:Aiming at the problems of low sweep coefficient and low oil-washing efficiency of steam flooding for heavy oil，a high-temperature-resistant channeling plugging agent was prepared with petroleum resin particle， anionic surfactants and water-soluble high molecular polymer. The carboxylate surfactant and the sulfonate surfactant were compounded with a mass ratio of 1.5∶1 to obtain oil-washing agent. The compound profile-control and oil displacement technology of channeling plugging agent and oil-washing agent was investigated by physical simulation experiment. The injection and plugging properties of channeling plugging agent，as well as the ability of the compound profile-control and oil displacement system to improve the recovery of steam flooding were investigated. The results showed that the channeling plugging agent had good injection and plugging properties，and had good erosion resistance at a high temperature of 250℃. The channeling plugging agent had better injection performance for the core with the permeability greater than 3.0 μm2. The plugging rate could be maintained above 90% for the core with the permeability about 5.0 μm2，and the reduction of plugging rate was less than 2% after flooded 20 PV steam at 250°C. The oil-washing agent could reduce the oil-water interfacial tension to 10-3 mN/m，and the oil-washing efficiency at 90—250℃ was greater than 40%. The use of oil-washing agent alone in steam flooding could only increase the recovery by 14%，while the use of channeling plugging agent and oil-washing agent compound system could increase the recovery by 26%. The combination of channeling plugging agent and oil-washing agent in steam flooding could effectively block the steam channeling，increase oil displacement efficiency，and improve the development effect of steam flooding in heavy oil reservoir.

Abstract:Novel surfactant SOE containing fluorine and a sulfonic group was synthesized using 1H，1H，2H，2H-Perfluoro- 1-decanol and sodium 2-chloroethanesulphonate in order to increase the permeability of aqueous phase and decrease the capillary pressure in ultra-low permeability sandstone reservoirs. This aimed to reduce injecting pressure and increase the amount of injected water. Moreover，SOE was combined with octylphenol polyoxyethylene（10）ether（OP-10）and sodium dodecyl benzene sulfonate （SDBS）respectively. The surface tension，oil-water interfacial tension and contact angle of SOE solution and the composite systems were investigated. The results showed that the surface activity and water non-wettability of SOE were obviously better than those of hydrocarbon surfactant and the interface activity of SOE was remarkably better than that of perfluorinated surfactant. The critical micelle concentration of SOE was 0.4 g/L in water or 30 g/L NaCl solution at 30°C. The oil-water interfacial tension of SOE solution was 2.80 mN/m，and the contact angle was up to 75.63° for this brine at this temperature. The synergism between SOE and hydrocarbon surfactant was good. When 0.08 mmol/L SDBS was added to 0.2 g/L SOE brine，the oil-water interfacial tension decreased obviously from 3.71 to 0.44 mN/m，and the contact angle changed slightly and remained 66.42°. Moreover，the amount of SOE would be decreased remarkably. The oil-water interface activity of SOE/SDBS composite system was markedly better than that of SOE/OP-10 in the brine. Therefore，the SOE/SDBS composite surfactant could be applied in the depressurization and injection augment for ultra-low permeability reservoir.

Abstract:In order to research the relationship between emulsifying and oil recovery of surfactant-polymer （SP） compound flooding for the conglomerate reservoir，by controlling the emulsifying intensity and the migration law of emulsifying system in long core，the oil displacement effect of binary compound system of partially hydrolyzed polyacrylamide（HPAM）and naphthenic sulfonate surfactant（KPS）with different emulsification intensity was studied，the effect of emulsifying degree on EOR was clarified. The experiment results showed that the medium emulsified SP system with oil-water interfacial tension（IFT）of 5×10-2 mN/m had 8% oil displacement efficiency more than the non-emulsified SP system with IFT of 5×10-3 mN/m. When the critical viscosity of SP system reached，the emulsion with IFT of 5×10-2 mN/m and suitable emulsion composite index could compensate the viscosity of oil displacement system and keep the stability of the viscosity of oil displacement system for a long distance，which was beneficial to EOR. In the multi-factor coupling of EOR decision system for conglomerate reservoir in SP compound flooding， the oil recovery could be increased by adjusting the viscosity ratio of flooding system and emulsion composite index when the permeability range was large. When the permeability ratio was less than or equal to 6，the oil recovery could be greatly improved by controlling the IFT and emulsion composite index. When the remaining oil saturation was less than 50%，the emulsion composite index was controlled at 50%—70%. While the former was more than 50%，the latter was controlled at 30%—50%. The SP compound flooding technology with low IFT and controllable emulsification was implemented in Xinjiang oilfield，the oil recovery rate increased by 28% and the reduction of water content decreased by more than 40%，which realized the personalized design of step-by-step viscosity reduction and step-by-step mobilization of oil displacement system.

Abstract:In order to clarify the relative importance of ultra-low interfacial tension（IFT）and emulsification mechanisms for recovering heavy oil by compound flooding，the IFT，emulsification，foam and oil displacement performances of two compound systems guided by ultra-low IFT and good emulsification were studied. The results showed that，for the ultra-low IFT system，the oil-water IFT could be reduced to 2.6×10-4 mN/m，but it performed poorer in foaming and stabilizing emulsion and foam than the emulsified compound system，while the oil-water IFT of the later was only 0.25 mN/m. Although the properties of those two systems differed greatly，the increased oil recovery by ultra-low IFT system was similar to that of emulsion system during the simple compound flooding，which might be caused by the poor sweep volume during flooding. However，that increased by ultra-low IFT foam was 38.3%，which was much higher than that of 28.9% by emulsion foam flooding. This indicated that the mechanism of oil washing by ultra-low IFT was more critical than that of viscosity reduction by oil-in-water emulsification during foam flooding. Ultra-low IFT foam flooding （water alternative gas injection） could improve heavy oil recovery more than increasing the slug of compound system. The recovery could be increased to 38.3% by 0.3 PV the former strategy，while 30.7% by 0.5 PV the latter. Ultra-low IFT foam flooding was the better way to improve heavy oil recovery at the present，and the displacement of heavy oil by single compound system might be a waste of chemical agents.

Abstract:In order to solve the problem of demulsification and flocculation of seawater-based drilling wastewater（SDW）treated by non-acidic non-oxidants in offshore oilfields，a cationic gemini demulsification flocculant was obtained by synthesizing dihexadecyl dimethyl ammonium bromide（DB）and compounding cationic polyacrylamide CPAM，reverse phase demulsifier OT and polyaluminium chloride PAC. The influence of pH value，reagent dosage and temperature on the treatment effect of seawater-based waste drilling fluid was evaluated. The mechanism of demulsification and flocculation of DB was analyzed. The SDW was characteristic of higher mineralization，oil content（753.01 mg/L），suspended solid content（75000 mg/L），larger viscosity（75 mPa s），and higher Zeta potential（-47.4 mV）absolute value，so it had strong stability. At room temperature（24℃） and pH=11，when PAM dosage was of 10 mg/L，PAC dosage was of 470 mg/L and OT dosage was of 370 mg/L，the oil content of supernatant of SDW after treatment decreased to 99.37 mg/L，suspended solid content decreased to 347.43 mg/L，Zeta potential increased to -20.1 mV，and the viscosity decreased to 23.1 mPa s. Furtherly，after adding 57 mg/L DB，the suspended solids content decreased to 25.8 mg/L，the removal rate of suspended solids was 99.97%；the content further decreased to 24.5 mg/L，the oil removal rate was 96.7% ；the Zeta potential increased to -9.8 mV，and the viscosity decreased to 14.9 mPa s. The demulsification and flocculation effect was excellent，indicated that there was positive synergy among DB，CAPM，OT and PAC. The corrosion rate of the supernatant to N80 steel sheet was only 0.01 mm/a，which was lower than 2.33 mm/a，the industry corrosion protection standard（60℃，first-class sea area，N80 steel）. When the SDW was treated with DB CAPM，OT and PAC synergistically，the obtained supernatant met the standard of discharge and reinjection，and could be used to reprepare drilling fluid，achieving the purpose of high-efficiency treatment of seawater-based drilling wastewater by non-acid and non-oxidant.

Abstract:Aimed at the problem of spontaneous imbibition physical simulation test using volume method and weighing method，In this paper，a set of device and method for measuring the efficiency of spontaneous imbibition and displacement in low permeability reservoir was developed. Through the innovative design of experimental method and device，the traditional volume method and weighing method were effectively combined to realize the mutual verification of the two data and improve the reliability of the experimental results. A low-permeability core was used to verify the operability of the device and method. The study of self-priming oil displacement efficiency in low permeability reservoir plays a positive role.

Abstract:After more than half a century's development，the oilfield chemical chemicals have become an indispensable materials for oil and gas production. However，the harsh oil and gas environment such as low permeability，high temperature and high salinity also poses new challenges to the research and development of organic oilfield chemical materials such as polymers and surfactants. The traditional "passive resistance" strategy cannot fully meet the requirements. In this paper，a new idea of "environmentally self-adaptive oilfield chemical materials" was proposed. Based on the author's own work，the principle， performance and potential of permeability adaptive polymer，temperature-adaptive polymer and surfactant，salinity-adaptive polymer，CO2-adaptive viscoelastic surfactant and pH adaptive viscoelastic surfactant were introduced on principle，properties and potential applications. Finally，the future trend of environmentally adaptive materials used in oil and gas production was prospected.

Abstract:Deep profile control technology is an important means to overcome the current situation of reservoir and achieve deep， precise and collaborative development. On the basis of fully analyzing the existing problems of oil reservoirs，this paper summarizes the principles and methods of the deep profile control technology of gel，jelly，granular，foam，microorganism and other low cost wastes，points out the advantages and problems of each system，summarizes the application of various system，in the field at home and abroad，and puts forward the next development trend for China's oil fields.

Abstract:In order to reduce the miscibility pressure between CO2 and crude oil and improve the oil displacement efficiency of CO2 miscible flooding，three methods to reduce the miscibility pressure were summarized，including miscible solvent，supercritical CO2 microemulsion and CO2-soluble surfactant. The structure characteristics of CO2-soluble surfactant and its mechanism of reducing the miscibility pressure of CO2 were analyzed. The miscible solvent method required a large amount of hydrocarbon gas and the cost was high. Supercritical CO2 microemulsion method could reduce the miscibility pressure to a certain extent，but the degree of reduction was relatively low. CO2-soluble surfactant could dissolve in CO2 so that CO2-soluble surfactant could act on the oil and gas interface，reduce the interfacial tension of oil and gas，and reduce the miscibility pressure. However，there were few kinds of CO2-soluble surfactants at present. Therefore，it was urgent to develop new CO2-soluble surfactant to improve the miscibility of CO2 and crude oil，and achieve high efficiency development of CO2 miscible flooding for crude oil.

Abstract:In-depth study of the interactions occurring between emulsion droplets is important to a range of applications from the food and pharmaceutical industries to oil recovery and mineral flotation. The traditional method of studying the stability of dispersion system is mainly based on the judgement of macroscopic properties of large number of particles. However，it is not mature to study the stability mechanism of emulsion by studying the interaction force between single droplets. The stability mechanism of emulsion can be directly elaborate by measuring the interaction force between monodisperse droplets. Based on the classic DLVO theory，the model of steric repulsion and depletion attraction，the surface force apparatus，atomic force microscope， total internal reflection microscope and optical tweezers were used to directly determine the interaction force between liquid and liquid interface. In this paper，the feasibility，principle and characteristic of the above measurement technologies applied to measure the interaction between droplets in emulsion were mainly reviewed，the advantage and disadvantage of different test methods for measuring the interaction force between droplets were compared，which provided reference for further research on the microscopic mechanism of emulsion stability.