Oilfield Chemistry (ISSN 1000–4092, CN 51–1292/TE), founded in 1984, is a quarterly journal issued on the 25th of the last month of each season. The journal is governed by China National Petroleum Corporation, and sponsored by the Polymer Research Institute of Sichuan University and State Key Laboratory of Polymer Materials Engineering (Sichuan University). It is a scientific journal distributed domestically and internationally. The Editor-in-Chief is Prof. ZHANG Xi, and the deputy Editor-in-Chief is Prof. HUANG Ronghua.

 

Aim and Scope

The journal aims to facilitate academic communication between the petroleum industry and the fields of chemistry, chemical engineering, biochemistry, and engineering.

 

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    Volume 41,2024 Issue 2
    • PAN Lijuan, CHENG Zhongfu, FANG Junwei, FANG Yuyan, WEN Jiantai, LYU Junxian

      2024,41(2):191-199, DOI: 10.19346/j.cnki.1000-4092.2024.02.001

      Abstract:

      In addressing the persistent challenge of rheological control in high-temperature and high-density water-based drilling fluids(WBDFs),a new high-temperature zwitterionic polymer viscosity reducer(HP-THIN)was prepared based on molecular structure optimization design and monomer optimization using orthogonal experiments and single-factor experiments. The molecular structure,thermal stability and relative molecular weight of HP-THIN were characterized and determined by infrared spectroscopy,Ulrich viscometer,and thermogravimetric analysis. The viscosity-reducing ability of HP-THIN on different types of drilling muds such as freshwater mud,salt-containing mud,calcium-containing mud,and high-density composite salt-containing mud was investigated at the temperature of 220 ℃. The effects of HP-THIN on adsorption capacity,zeta potential,and particle size of base-mud clay were tested at ambient temperature and compared with similar commercial viscosity reducers Polythin and xy-27. The results showed that,the optimal reaction recipe of the HP-THIN was as follows,the reaction temperature was 60 ℃ ,thereaction time was 3 h,the amount of initiator and chain transfer agent was 1%(based on the total amount of monomers),and the total mass fraction of the monomer was 30% and the molar ratio of AM,AA,AMPS and PTM was 1.9∶7.5∶2.1∶1. The viscosity-average relative molecular weight of the obtained HP-THIN was about 8211,and the HP-THIN exhibited good thermal stability. After aging at the temperature of 220 ℃ ,the viscosity reduction rates of HP-THIN at the optimal dosage of 0.3% on freshwater-based mud,salt-water-based mud,calcium-containing base mud,and high-density composite salt-water-based mud reached 86%,72%,73%,51%,respectively. Compared to xy-27 and Polythin,HP-THIN demonstrated better high-temperature viscosity reduction effect in all different types of drilling fluid base mud due to its strong adsorption capacity with clay platelets, large absolute value of zeta potential,which was conducive to unentangling the complex polymer network structure between clay particles,significantly decreasing the viscosity of the drilling fluid,showing good application prospects.

    • SUN Fanglong, LI Ruigang, SONG Yuancheng, JIAO Yan’an, ZHAN Fubin, TANG Hua

      2024,41(2):200-206, DOI: 10.19346/j.cnki.1000-4092.2024.02.002

      Abstract:

      In order to enhance the plugging performance of oil-based drilling fluids, a hybrid core-shell calcium carbonate-polyurethane well wall reinforcer was prepared via hydrothermal synthesis using calcium chloride,sodium carbonate, glutamic acid,2,4-toluene diisocyanate and dibutyltin dilaurate as raw materials. The effects of well wall reinforcer dosage on the rheological properties,stability and plugging performance of base slurry were investigated by measuring rheological parameters, demulsification voltage,filtration loss and invasion depth. The well wall reinforcer was compounded with some materials such as potassium titanium oxide fibers,sepiolite,diatomite and asphalt oxide. The effects of the compounded well wall reinforcer on the wetting properties,rheological properties,stability,plugging performance,and temperature resistance of the oil-based drilling fluids were studied. The results showed that the well wall reinforcer,with polyurethane as the shell and calcium carbonate microsphere as the core,had a microsphere diameter about 2 μm,exhibited minimal influence on the rheological properties and stability of base slurry,and significantly improved the plugging performance of base slurry. A dosage of 2.5%—3.0% achieved good plugging effects,with a demulsification voltage of 525—542 V and an invasion depth of 0.6 cm. The compounded well wall reinforcer with optimum formula significantly improved the wetting properties of oil-based drilling fluids,had little influence on the rheological properties of base slurry,and helped enhance stability. The demulsification voltage increased to 637 V. The various components of the compounded well wall reinforcer exerted synergistic effects,effectively plugging cracks with different pore sizes,and then exhibited good filtration loss performance. The filtration loss and invasion depth at room temperature were 1.0 mL and 0.2 cm,respectively. After aging at 180 ℃ for 8 hours,the compounded well wall reinforcer still maintained good filtration loss performance. The filtration loss and invasion depth were 3.3 mL and 0.3 cm,respectively,indicating good temperature resistance. The polyurethane soft shell of the well wall reinforcer facilitated the microspheres entry into the leading edge of induced fractures,while the calcium carbonate hard core dispersed stress and prevented further crack extension,effectively plugging the wellbore cracks. Additionally,it exhibited good compatibility with drilling fluids and excellent plugging performance.

    • HOU Yegui, DAI Rongdong, SUN Lijun, WANG Zhiwei, YU Shaoqing, WANG Kai, WANG Jian

      2024,41(2):207-211, DOI: 10.19346/j.cnki.1000-4092.2024.02.003

      Abstract:

      An acid-soluble weighting agent was prepared using hydroxyapatite as raw material and sodium hexametaphosphate as modifier. The chemical structure of sample was characterized by FTIR. The acid solubility,Zeta potential,and wettability of the modified weighted agent were evaluated. Finally,the influence on the rheology and the filtrate loss of drilling fluids as well as the reservoir protection effect was analyzed. The results indicated that the solubilization rate of the modified weighting agent under 10% HCl solution was up to 88.27%. Drilling fluids with modified weighting agents had good rheology and filtration loss reduction properties. The permeability recovery value of the core contaminated by the drilling fluid mixed with modified weighting agent was >90% after soaking in 10% HCl solution for 2 h,which showed that the mud cake formed by the participation of modified weighting agents could be effectively dissolved and removed under the effect of acidic,thus protecting the reservoir.

    • WU Shaowei, YIN Jinrong, LI Zhenyong, ZENG Zhen, XU Min, REN Xianyan

      2024,41(2):212-219, DOI: 10.19346/j.cnki.1000-4092.2024.02.004

      Abstract:

      To avoid the use of organic solvents and improve the problem of self-generated proppants easy to aggregate during growth in the well,an environmentally friendly self-generated proppant was designed using styrene(St)and divinylbenzene (DVB)as phase change component,and aqueous solution containing dispersants as non-phase change one. By adjusting the composition and dosage of dispersants in non-phase change component and the speed of pre-mixing of the two phases,the optimum formula and preparation process of self-generated proppant were determined. The morphology and structure of self-generated proppant were analyzed by scanning electron microscope,X-ray diffraction analysis and infrared spectroscopy. Furthermore,its performances were evaluated by particle strength tester and constant load tester. The results showed that,the pre-mixing speed of the two phases was determined to 120 r/min. The dispersants in non-phase change component was polyvinyl alcohol-1788, methylcellulose and sodium dodecyl benzene sulfonate in mass ratio of 5000∶175∶2. When the reaction was standing at a simulation fractures temperature of 100 ℃,the liquid-solid phase transition time of self-generated proppant was 32.5—40.0 min,and then the rapid increase in strength was achieved about 24 min after the phase transformation. The yield of single particle dispersed proppant could reach 78%. Meanwhile,the size of 60% proppant particles could be controlled in 0.850—0.425 mm(20—40 mesh). The self-generated proppant particles had maximum single particle strength about 32 N,an apparent density of about 1.18 g/cm3,a degree of sphericity of about 0.9 and a low acid solubility of 2.47%. The single particle strength of self-generated proppant was comparable to that of commercially available ceramic proppant,while significantly higher than that of quartz sand proppant. Its acid resistance was significantly higher than that of both. The proposed self-generated proppant and its construction method improved the problems of easy aggregation,low yield and low microsphere formation yield of the self-generated proppant under the absence of shear force. Furthermore,the phase-change solution here did not need to add any organic solvents and is environmentally friendly. It had great potential for deep reservoir exploitation.

    • YANG Yukun, LI Junhan, YU Ming, YANG Simin, AO Hongdan, LUO Pingya, LIN Ling

      2024,41(2):220-228, DOI: 10.19346/j.cnki.1000-4092.2024.02.005

      Abstract:

      The adsorption and retention of polymers on the surfaces of oil and gas reservoir rocks play a significant role in the optimization of drilling fluid formulations and enhancing the economic benefits of unconventional oil and gas reservoirs. In this study,the adsorption of partially hydrolyzed polyacrylamide(HPAM),partially hydrolyzed poly(acrylamide/ diallyldimethylammonium chloride)(HPAD),and hydrophobically associating polyacrylamide(HAP)on shale,coal rock,and sandstone surfaces was indirectly measured by starch cadmium iodide method. The adsorption quantities were quantified. The effects of adsorption time,polymer concentration,temperature,and salinity on the adsorption behavior of the three polymers on rock surfaces were analyzed. The results indicated that the adsorption of HPAM and HAP on rock surfaces conformed more closely to the pseudo-second-order adsorption kinetic model,while that of HPAD adhered more closely to the pseudo-first-order adsorption kinetic model. Compared with HPAD and HAP,HPAM exhibited a higher equilibrium adsorption capacity. The adsorption processes of all three polymers on reservoir rocks better fit the Freundlich adsorption model. The time required to reach adsorption equilibrium was closely related to the polymer and the type of reservoir rock. The adsorption of HPAM reached saturation on the surfaces of all three rock types,while the adsorption of HPAD and HAP increased over time. An increase in temperature intensified desorption,resulting in a decrease in adsorption quantity. Conversely,an increase in salinity reduced the solubility of polymers, leading to an increase in adsorption quantity. The continuous adsorption of polymers on reservoir surfaces was the main reason for their consumption in drilling fluids. The sustained adsorption of HPAD and HAP on reservoir rock surfaces might result in the failure of drilling fluids due to their low concentrations.

    • LI Jiaming, LYU Dongfang, ZHAO Jinzhong, ZHAO Guang, DAI Caili

      2024,41(2):229-237, DOI: 10.19346/j.cnki.1000-4092.2024.02.006

      Abstract:

      The frequent water gushing in sandstone mining strata of Luohe Formation has seriously affected the safety production of the mine. The traditional grouting systems are faced with the problems of serious percolation effect and uncontrollable gelation performance,which is difficult to achieve effective regulation of fissure water. In this work,the microscopic characteristics of sandstone pores were clarified by analyzing the mineral composition and microscopic morphology of five typical natural core samples, such as gravel-bearing sandstone, giant sandstone, coarse-grained sandstone, medium-grained sandstone, and fine-grained sandstone. A solid-free gel system with low cost and excellent stability was constructed for grouting. The injectivity and plugging performance of the gel grouting system were studied by physical simulation displacement experiment. The pore distribution characteristics in the core before and after grouting were studied by nuclear magnetic resonance online displacement experiment. The results showed that the small pore diameter and poor connectivity were the geological reasons for the difficulty of smooth injection and long-distance migration of the traditional grouting systems. Due to the existence of percolation effect,the curing and plugging effect of traditional grouting system was obviously lower than that of theoretical design. A novel gel grouting system with low cost,solid-free,good injection,and long-distance migration performance was constructed by using 0.5%—0.6% polyacrylamide,0.6%—0.7% organic amine monomer crosslinking agent,0.07%—0.08% phenolic monomer crosslinking agent and 0.2%—0.3% organic acid regulator as raw materials. The gel grouting system could achieve gelation within 48 h,meanwhile, had no obvious dehydration within 180 days,showing excellent long-term aging stability. The gel grouting system had good injectivity. The pressure attenuation ratio was 7.85% —20.95% ,meanwhile,the plugging ratio was 82.04% —92.19% after continuous flooding. The gel grouting system increased the seepage resistance and blocked the subsequent fluid by occupying the large channel or fracture space,which realized the effective plugging of the water layer. The research results could provide new ideas for the grouting and water plugging construction of sandstone in Luohe Formation sandstone.

    • LIU Yiwen, FU Meilong, WANG Changquan, XU Shijing, MENG Fankun, SHEN Yanlai

      2024,41(2):238-244, DOI: 10.19346/j.cnki.1000-4092.2024.02.007

      Abstract:

      CO2 flooding is an effective technical measure for tertiary oil recovery in high water cut reservoirs. Using the existing well pattern to inject CO2 is an economical and feasible development method under low oil price. Although the particle migration caused by the displacement process will block the pore throat of rock,the injection of CO2 can effectively reduce the injection pressure,and the dissolution occurred during the injection process improves the seepage capacity of fluid as a whole. By carrying out the experiment of particle migration plugging law after CO2 flooding and the evaluation experiment of CO2-aqueous solution on rock dissolution,and evaluating the variation characteristics of relative permeability curves before and after displacement,the influence of CO2 flooding on reservoir seepage capacity was further explained. The results showed that during the injection of CO2, the injection pressure decreased when the injection rate was 0.1 mL/min and 1.0 mL/min. The core permeability loss was 37.05% after CO2 flooding under the condition of oil,while the core permeability recovery was 30.48% after cleaning the core with toluene and anhydrous ethanol,indicating that the particles would be bound by crude oil during the migration process,accumulate into clusters,and cause blockage. Although there was a certain blockage,the CO2-aqueous solution mainly reacted with chlorite and released Ca2+,Mg2+,Fe2+ and other ions. The concentration of Ca2+ increased by 137.05%,the concentration of Mg2+ decreased by 52.20%,and then the concentration of Fe2+ decreased by 49.45%. It showed that although the generated MgCO3 and Fe2O3 would block the pore throat of rock,the dissolution of CaCO3 by CO2 was stronger,which improved the seepage capacity of the fluid as a whole,thus improving the water injection capacity and the effect of subsequent water flooding to a certain extent. The irreducible water saturation in the relative permeability curve before and after CO2 flooding increased,the residual oil saturation decreased,the two-phase seepage area increased,and then the oil displacement efficiency increased. It further indicated that the dissolution produced by CO2 flooding increased the pore space and seepage channel as a whole,and then improved the injection capacity of injected water.

    • WU Ke, WEN Shoucheng, SHAOWei, XU Mingbiao

      2024,41(2):245-250, DOI: 10.19346/j.cnki.1000-4092.2024.02.008

      Abstract:

      The fracture structure of the Chang 8 reservoir in the Honghe oilfield is complex,which belongs to a low porosity and ultra-low permeability reservoir. The reservoir heterogeneity is strong and the residual oil saturation is high. Because the water phase permeability is low,and the water injection pressure rises rapidly,which exceeds the fracture restart pressure,resulting in serious water channeling and poor effect of water injection development. Combined with the characteristics of nano and microemulsion,a nano-SiO2 microemulsion depressurization and injection-augmenting system was designed,and the temperature resistance, interfacial tension reduction ability,solubilization and formation compatibility of the system were systematically evaluated,and the core depressurization and injection-augmenting displacement experiment was carried out. The experimental results demonstrated that the nano-SiO2 microemulsion system not only exhibited excellent temperature resistance and salt resistance but also possessed high interfacial activity,reducing the oil-water interfacial tension to approximately 10-2 mN/m. The system showed good oil solubilization performance with a solubilization amount of 6.5 mL/30 mL. Simultaneously,the core pressure reduction and injection increase experiment indicated that after injecting 2 PV of 1% the nano-SiO2 microemulsion system into the cores with the permeability of 0.4 × 10-3 μm2, the pressure reduction efficiency exceeded above 28% . The depressurization and injection-augmenting effects of the system were evident,meeting the requirements of the field.

    • LIANG Tuo, YANG Changhua, WANG Huipeng, ZHANG Yongwei, WANG Chen, QU Ming, HOU Jirui

      2024,41(2):251-258, DOI: 10.19346/j.cnki.1000-4092.2024.02.009

      Abstract:

      Nanofluids have become a popular research topic in oil and gas exploration and development due to their potential to enhance oil recovery. the shrinkage behavior of solid-interface oil film was investigated when contacting with 50 mg/L modified lamellar nanofluid in a self-made visualization model. Additionally,oil sand washing experiments were also conducted to determine the oil washing efficiency of the modified lamellar nanofluid at a concentration of 50 mg/L under different conditions. The results showed that the solid-interface oil film shrunk slowly and no wedge-shaped region was observed under simulated formation water condition. However,under the modified lamellar nanofluid environment,the solid-interface oil film shrunk significantly with an obvious wedge-shaped region and two contact lines including an outer contact line and an inner contact line. The shrinkage rate of the outer contact line was 8.5817×10-5 cm/s while the shrinkage rate of the inner contact line was 0.6617×10-5 cm/s. The results from oil sand washing experiments exhibited that the oil-washing efficiency of the modified lamellar nanofluid increased with the increase of oil sand particle size and temperature. What’s more,the oil-washing efficiency also increased rapidly at first,followed by a slow increase as the oil sand immersion time was extended,with an optimal immersion time of(8±2)hours. The oil-washing efficiency of the modified lamellar nanofluid could reach as high as 95.7%. These achievements break through the limitation that only high-concentration spherical nanoparticles can form structure disjoining pressure,providing a possibility for the applications of lamellar nanofluid in oilfield and a technical reference for pilot construction processes.

    • SHU Zheng, XIONG Ying, XU Chengjun, ZHAO Wanwei, FENG Rusen

      2024,41(2):259-264, DOI: 10.19346/j.cnki.1000-4092.2024.02.010

      Abstract:

      Water invasion in carbonate rock gas reservoirs with water can greatly reduce the production. In view of this problem,the surface of carbonate rock was superhydrophobically modified by interface modifier(silane coupling agent). The influence of interface modification on the percolation ability of water phase,gas phase and gas-liquid two-phase was studied through porous medium flow experiments. The results showed that when the mass fraction of interface modifier was 3%,the contact angle between modified carbonate rock and water was 153°,and then the interface of the carbonate rock reached a superhydrophobic state。Under the condition of superhydrophobic carbonate rock and single-phase constant pressure(0.05—0.40 MPa)injection,the seepage velocity of single water phase was increased by 72.1%—85.9%,and that of single gas phase was increased by 52.9%—72.5%, compared with that before modification(contact angle 0°). Under the condition of two-phase flow with gas phase constant pressure (0.3 MPa)and water phase constant flow(0.05—0.20 mL/min),the outlet time of sand filling pipe was reduced by 41.0%— 47.4%,and the seepage velocity of gas phase was increased by 102.1%—104.5% . When gas phase and water phase were both two-phase flow with constant pressure(0.07—0.30 MPa),the amount of water phase entering the pores was reduced by 75.6%— 100.0% ,and the seepage velocity of gas phase was increased by 111.1% —200.0% after the interface of carbonate rock was modified to superhydrophobic. By modifying the superhydrophobic interface in the near wellbore zone of gas reservoirs with water, the capillary force of water phase in the pores became resistance. It could effectively prevent formation water from entering the pores of near wellbore zone and reduce the degree of water invasion. At the same time,it could reduce the viscous friction force of gas phase on the pore surface,and then the water phase produced a“slip effect”at the interface,reducing the seepage resistance of gas and water phases,ultimately increasing the production of gas reservoir.

    • MA Chao, GAO Shengtian, WANG Cheng, LIU Xin, HUANG Xiaoyi

      2024,41(2):265-272, DOI: 10.19346/j.cnki.1000-4092.2024.02.011

      Abstract:

      Aiming at the limitations of conventional kinetic inhibitors,such as low tolerance to subcooling and short induction time in hydrate formations,a novel kinetic inhibitor P(NVP-g-NVCL-g-DMAEMA)was synthesized from N-vinylpyrrolidone(NVP), N-vinylcaprolactam(NVCL)and dimethylaminoethyl methacrylate(DMAEMA). The supercooling degree and induction time in the simulated gas hydrate inhibition processes were used as indexes to optimize the synthetic parameters. The product structure was characterized using infrared spectroscopy,while molecular dynamics simulation software extensively simulated the inhibition process and revealed the mechanism of hydrate kinetic inhibitors. The results showed that the optimum reaction condition was obtained as follows:8∶20∶1 mass ratio of NVP,NVCL and DMAEMA,0.5% initiator(1∶1 mass ratio of ammonium persulfate and sodium bisulfite)in total mass of monomer,65 ℃ reaction temperature and 6 h reaction time. When the mass fraction of inhibitor was 1.0%,the supercooling degree of hydrate formation increased from 2.6 ℃ to 9.6 ℃ under atmospheric pressure, meanwhile the induction time extended from 20 min to 945 min. The inhibition mechanism was mainly driven by inhibiting the formation of hydrate via hydrogen bond adsorption between the carbonyl groups on the five-membered ring or the seven-membered ring of molecular chain,as well as that on the ester group,and the water molecule. Nitrogen atoms on the molecular chain also formed hydrogen bonds and contributed to the adsorption. Furthermore,the steric hindrance of inhibitor also prevented the aggregation of hydrate molecules and thus inhibited the crystallization of hydrate. The kinetic inhibitor not only had active groups that could form hydrogen bonds to enhance the adsorption of inhibitor on hydrate cage,but also had alkyl chains that could affect the movement and distribution of methane molecules,further improving the supercooling degree and prolonging the induction time.

    • JIANG Jianlin, QIN Bing, CAO Fengyi, QIAO Fulin

      2024,41(2):273-279, DOI: 10.19346/j.cnki.1000-4092.2024.02.012

      Abstract:

      To address the issues of poor efficiency of water flooding and low swept volume of chemical viscosity reducers for the conventional heavy oil development,a composite oil displacement system with viscosity reduction and foaming features was developed by using N,N-dimethylamine,sodium 3-chloro-2-hydroxypropane sulfonate and alkyl alcohol polyoxyethylene ammonium sulfate as raw materials. The effects of partially hydrolyzed polyacrylamide(HPAM)on emulsification and viscosity reduction of heavy oil,as well as the effects of polymer,reservoir pressure and heavy oil on the foaming ability and stability of oil displacement system were systematically investigated. The heavy oil recovery of polymer/viscosity reduction composite flooding with and without foam flooding was compared. The results showed that the introduction of HPAM improved the viscosity reduction ability of composite oil displacement systems at the lower concentrations. Under the temperature of 30—80 ℃、mass fraction of 0.3% and an oil-water volume ratio of 7∶3,the composite oil displacement system(referred to as SKY)could reduce the viscosity of heavy oil from 1607 mPa·s to 35.0—60.3 mPa·s,and then reach a high viscosity reduction rate of 96%. Meanwhile,SKY also exhibited excellent foaming performance. The stability of foam was significantly enhanced with the increase of reservoir pressure and heavy oil content. The half-life of foam increased from 8 min to 120 min when the pressure rose from 1 MPa to 13 MPa at 70 ℃. Heavy oil had obvious effect of stabilizing foam. The polymer improved the stability of foam mainly by increasing the viscosity,reducing the drainage rate of foam liquid membrane,and enhancing the strength of membrane. The physical simulation flooding experiments revealed that the polymer/viscosity reduction composite flooding system improved the recovery rate of heavy oil by 10.05 percentage points. After the injection of polymer/SKY and nitrogen,the effect of combination flooding was greatly improved. The produced foam after the injection of gas enhanced sweep efficiency during displacement,so the recovery rate of polymer/viscosity reduction/foam combination flooding was increased by 22.0 percentage points. Therefore,the viscosity reduction/ foam combination flooding technology could realize the integration of viscosity reduction and profile adjustment,which had great application prospects for enhancing heavy oil recovery by water flooding.

    • WANG Qie, FAN Yonghong, GUO Bin, MEDINUEL, QIN Xinzheng

      2024,41(2):280-287, DOI: 10.19346/j.cnki.1000-4092.2024.02.013

      Abstract:

      In order to explore the effect of RhlA and RhlB gene expression on viscosity reduction in microbial oil recovery,a real-time fluorescent absolute quantitative(Q-PCR)method for RhlA and RhlB genes was established,and the Pseudomonas aeruginosa X7 fermentation broth and Karamay Oilfield at different culture stages were detected. The expression levels of RhlA and RhlB genes in different formation waters were measured,and their rhamnolipid production,surface activity,emulsifying activity, emulsifying stability,and crude oil viscosity reduction rate were determined. The results showed that the expression levels of RhlA and RhlB genes were positively correlated with rhamnolipid production,surface activity,emulsifying activity and crude oil viscosity reduction rate. With the increase of fermentation time,the expression levels of RhlA and RhlB genes in the fermentation broth increased continuously and reached the maximum at 24 h,then decreased and stabilized at 60 h,and the maximum expression levels of RhlA and RhlB genes were 2.51 × 106 and 3.25 × 105 copies/μL. The highest expression level of RhlA and RhlB genes reached the maximum value of 824.08 mg/L at 60 hours. The surface activity of the fermentation broth,crude oil emulsifying activity and heavy oil viscosity reduction rate also increased with the increase of fermentation time and reached the maximum value at 24 hours,48 hours and 60 hours,respectively. The rhamnolipid crude extract in the fermentation broth had good stability and could work stably under certain extreme conditions. RhlA and RhlB genes probably affected microbial oil recovery by affecting rhamnolipid production,surface activity,emulsifying activity and viscosity reduction rate of crude oil. This study preliminarily revealed the influence of functional gene expression related to biological surface activity on the viscosity reduction effect of heavy oil,which was important to promote the industrial application of microbial oil recovery.

    • YUAN Fuqing, SONG Qian, JI Yanfeng, LI Haitao

      2024,41(2):288-295, DOI: 10.19346/j.cnki.1000-4092.2024.02.014

      Abstract:

      During the injection process into the formation,polymers undergo severe physical and chemical degradation,resulting in significant viscosity loss. In order to reduce the viscosity loss during the polymer injection process,the concept of partially cured polymer oil displacement technology is proposed. At 70 ℃,polymer systems with different viscosities and curing degrees ranging from 60% to 100% were prepared by varying the stirring time of mechanical stirrer. The study investigated the seepage characteristics and oil displacement performance of polymers with different curing degrees in porous media based on macroscopic and microscopic models. The results showed that compared to fully cured polymers,partially cured polymer systems exhibited better viscoelastic properties,enabled better mobilization of residual oil and improved microscopic oil displacement efficiency. Partially cured polymer systems could establish higher resistance coefficients and residual resistance coefficients,and then could retain higher effective displacement viscosities after shearing through porous media. The degree of polymer curing was too low to facilitate the entry of polymers into the deep part of reservoir. In polymer system with curing degree of 60%,the blockage mainly occurred near the injection end of sand-filled tube at 0—1/5 distance,while in polymer systems with curing degrees of 80% and 100%,the blockage mainly occurred near the injection end of sand-filled tube at 1/5—2/5 distance. Compared to water flooding,the incremental oil recovery rates of macroscopic oil displacement for polymer systems with curing degrees of 60%,80% and 100% were 26.2 percentage points,29.0 percentage points,and 23.3 percentage points,respectively. Meanwhile,the incremental oil recovery rates of microscopic oil displacement were 37.3 percentage points,44.9 percentage points,and 36.0 percentage points,respectively. For heterogeneous reservoirs,the residual undissolved polymer particles in partially cured polymers exhibited good plugging and conformance control properties. As a result,the liquid absorption in low-permeability layers was increased,the affected volume was expanded,and thus the recovery rate of low-permeability layers was enhanced. The research results could provide theoretical guidance for field tests of partially cured polymer oil displacement.

    • WANG Zhengbo, CONG Sunan, CHEN Weidong, HAN Yu, YANG Hao

      2024,41(2):296-301, DOI: 10.19346/j.cnki.1000-4092.2024.02.015

      Abstract:

      Aiming at the problem that there is no basis for selecting the molecular weight and concentration of polymer in the process of adopting the binary composite flooding in low permeability reservoir,the laser particle size analyzer is used to test the hydrodynamic dimensions of the binary compound flooding system under different conditions,and the change law of the hydrodynamic diameter of the binary compound flooding system with the molecular weight of polymer,the concentration of polymer,the concentration of surfactant and the mineralization degree of the base fluid was clarified. The average throat radius of cores with different permeability was tested by constant velocity mercury injection experiment,and the empirical formula of artificial core permeability and average throat radius was fitted. based on the injection test results of the binary flooding system and the judgment criteria calculated by the field data,it was clear that when the core permeability was less than 20 × 10-3 μm2 ,the molecular weight of the injected polymer should be less than 3 million and the concentration was less than 500 mg/L;when the core permeability was between 20×10-3 —40×10-3 μm2 ,the molecular weight of the injected polymer should be less than 5 million. When the core permeability was between 40×10-3 —70×10-3 μm2 ,the molecular weight of the injected polymer should be less than 12 million. The influence of the salinity of the binding base solution and the concentration of the surfactant on the hydrodynamic size of the binary system could provide guidance for the adjustment of the on-site binary system formula.

    • FU Jian, LIU Yulong, ZHANG Cenqian, WANG Chenyue, SUN Shanshan1, SHE Yuehui, ZHANG Fan

      2024,41(2):302-309, DOI: 10.19346/j.cnki.1000-4092.2024.02.016

      Abstract:

      Spontaneous imbibition is an important method for oil recovery in low permeability reservoirs. There are few reports on the main oil recovery mechanism of microbial enhanced imbibition recovery. In this paper,the patented strains of Brevibacillus potsdamus BS3096 and Pseudomonas aeruginosa LZ3-2 isolated from the reservoir environment in the laboratory were used. Through spontaneous imbibition experiments,the selection of bacteria and medium,the growth conditions of microorganisms,the metabolites of bacteria biosurfactants,the effects of bacteria and other factors on microbial enhanced oil recovery were studied. The experimental results showed that the imbibition fluid containing lipopeptide biosurfactant produced by BS3096 could reduce the oil-water interfacial tension from 0.8848 to 0.2055 mN/m,and the contact angle from 116.4° to 42.8°,so that the wettability of the rock changed from oil wet to water wet. The decrease of oil-water interfacial tension and the change of rock wettability had a significant effect on the recovery of imbibition crude oil. The imbibition recovery of lipopeptide biosurfactant produced by BS3096 could reach up to 60%. The recovery rate of rhamnolipid produced by Pseudomonas aeruginosa PAO1 was 56.26%. The glycoprotein bio-emulsifier produced by LZ3-2 had emulsifying effect on crude oil,and the emulsification rate was 6.96 %. In the imbibition experiment,BS3096 bacteria accumulated in the core,selectively blocked the large pore throat channel,and diverted the imbibition fluid to the small pores in the low permeability area to displace the crude oil,which could increase the recovery rate by 7.5 percentage point. Under the same experimental conditions and surfactant concentration,the order of spontaneous imbibition of biosurfactants and chemical surfactants was biotype > anion > nonionic > cation. The imbibition recovery of lipopeptide biosurfactants was 11.8—44 percentage point higher than that of chemical surfactants. This study provides an efficient,economical and environmentally friendly method for improving oil recovery in low permeability reservoirs,and provides theoretical support for the application of microorganisms and their metabolites in the field.

    • MIAO Wei, WANG Zhigang, LIU Yutang, LIU Jingjing, GUANG Yichu, ZHANG Rui

      2024,41(2):310-314, DOI: 10.19346/j.cnki.1000-4092.2024.02.017

      Abstract:

      In view of the problem that the production rules of conglomerate reservoirs with different modes in polymer/surface binary composite flooding stage have not fully been studied clearly,the residual oil distribution and pore production features of conglomerate reservoir at different stages of production were studied through indoor core oil displacement experiment combined with NMR online monitoring and CT scanning analysis. The results showed that the oil recovery of the single,dual and complex mode cores in the water drive stage was 31.4%,25.8% and 33.4%,respectively,while the enhanced oil recovery of the dual mode rock was higher than that of the complex mode rock and higher than that of the single mode rock in the binary composite flooding stage,which was 27.9,26.4 and 19 percentage points,respectively. Moreover,the pore limit of oil production was lower than that of the water production stage,and reduction amplitude of the complex mode core was higher than that of the single core and dual core. The heterogeneity of single,dual and complex mode cores was gradually enhanced,resulting in uniform displacement of single mode cores and high oil recovery in the water flooding stage. While the oil in complex mode rock was mainly concentrated at large hole with pore size of 32.7—52.5 μm,which was also largely produced in the water drive stage. In the dual modal conglomerate rock,the oil volume in the large pores was lower than that in the complex conglomerate rock,resulting in that the water flooding recovery rate was lower,and the remaining oil volume was higher. In the binary flooding stage,based on the effect of profile control and flooding and the influence of residual oil after water flooding,the dual mode core had the best effect of enhancing oil recovery,followed by the complex mode core.

    • FANG Xiaojun, BU Xiaoyang

      2024,41(2):315-321, DOI: 10.19346/j.cnki.1000-4092.2024.02.018

      Abstract:

      In order to improve the corrosion problem caused by acidizing fracturing,Schiff base acidizing corrosion inhibitor 1-phenyl-3-(1-cyclohexylamine)-propylene(PCP)was synthesized by cinnamaldehyde and cyclohexylamine. Its structure was characterized by infrared spectroscopy and gas chromatography-mass spectrometry. The corrosion inhibition effect of PCP was evaluated by weight loss method,electrochemistry(polarization curve,impedance spectrum,noise)and molecular dynamics simulation. The results showed that the synthesized product was the target product PCP. Under the condition of 15% HCl and 90 ℃, and with the increase of PCP concentration,the weight loss corrosion rate and corrosion current density of J55 steel decreased significantly,while the corrosion inhibition efficiency increased gradually. The corrosion inhibition efficiency could reach more than 99% under different PCP dosage,indicating good corrosion inhibition effect. When the dosage of PCP reached 0.15%,the overall corrosion rate and corrosion inhibition efficiency had little change with increasing concentration of corrosion inhibitor. That is,the adsorption concentration of corrosion inhibitor on the surface of J55 steel had reached the critical micelle concentration,so the adsorption amount did not change. PCP was a mixed corrosion inhibitor,which inhibited both cathode hydrogen evolution and anode dissolution reaction. With the increase of PCP concentration,the arc radius,polarization resistance and noise resistance were all arranged from small to large in following order:blank<0.05%<0.10%<0.15%<0.20%. The low frequency white noise level decreased with the increase of PCP concentration in the current PSD diagram. That is,the corrosion rate of J55 steel decreased continuously,which was consistent with the rule of weight loss method and polarization curve reaction. When PCP molecule adsorbed and balanced with the metal,the whole corrosion inhibitor molecule was in the same plane,and then adsorbed on the J55 steel surface in parallel to achieve complete coverage,thus effectively slowing down the immersion of corrosive medium.

    • NING Fanzhe, LI Zhi, LI Junliang, ZHANG Xiaochuan, GU Shaoxing, FENG Mingxi, MAPingang, WANG Jingqin

      2024,41(2):322-328, DOI: 10.19346/j.cnki.1000-4092.2024.02.019

      Abstract:

      The depth of Xushen gas field is greater than or equal to 3000 m,the well temperature is less than or equal to(le) 150 ℃ ,meanwhile,the climate character is long wintertime and low temperature. Aiming at these characteristics,the anionic surfactant palmitamide sulfobutyrate disodium (ASB-16A) was synthesized using maleic anhydride,cetamide and anhydrous sodium sulfite by two steps of amidation and sulfonation reaction. ASB-16A was mixed with foaming agent lauryl-glucoside (APG1214),antifreeze ethanol,and deionized water to prepare a bubble agent (CYY-1) with cold and high temperature resistance. The foam performance,high temperature resistance,low temperature stability and compatibility with formation water of CYY-1 were evaluated. Finally,CYY-1 was applied in Xushen gas field. The results showed that the optimum formula of CYY-1 was obtained as follows:10% ASB-16A,10% APG1214,44% ethanol,and deionized water. CYY-1 showed better foaming and steady blebbing properties. At 80 ℃,1.25% CYY-1 solution had an initial foam height of 150 mm,a foam height of 150 mm and 75 mm for 3 min and 5 min standing time,respectively,and a liquid volume of 1100 mL. The aging under weak base conditions, such as 8.5 pH value,150 ℃ and 24 hours,had little effect on the foam performance of CYY-1. The stability at low temperature of CYY-1 was better than that of commonly used low temperature bubble agent. After freezing at -35 ℃ for 7 d,CYY-1 became cloudy. But it could still flow in the pipeline,which met the requirements of automatic filling of device. The compatibility of CYY-1 with formation water was good. 0.5% —10.0% solution was still clear and transparent after standing for 48 hours at room temperature,so automatic bubble filling could be implemented. Two wells were tested in the field. The daily gas production of one well increased from 2.46×104m3 to 3.07×104m3. Meanwhile,the daily water yield decreased from 5.77 m3 to 3.70 m3. Stable carrying water production was achieved. CYY-1 was suitable for foam drainage gas production of well temperature le 150 ℃,salinity le 16 g/ L and pH value of 8.5.

    • LIUWan, SUN Tao, WU Hongjun, ZHANG Liang, BAI Xiaofei, ZHANG Lingqian

      2024,41(2):329-334, DOI: 10.19346/j.cnki.1000-4092.2024.02.020

      Abstract:

      The scale plugging problem is one of the main problems causing the production reduction of oil and gas fields. The common acid deplugging agent is highly corrosive,which affects the safe production of oil and gas wells. In order to solve the above problems,the HOMO/LUMO level and binding energy of chelating agents with metal ions were calculated by using Gaussian 09 software to optimize the molecular structure of several chelating agents. The chelating agent diethylenetriamine pentaacetic acid(DTPA)was selected. At the same time,computational chemistry was used to explore the mechanism of the compound detergent,and the synergistic effect between different additives was studied. On the basis of theoretical research,a non-acid scale removal agent system with DTPA as the main agents was developed:12% DTPA+0.3% scale inhibitor PASP+0.4% penetrant JFC. The scale dissolution rate of the system could reach more than 80% for a certain site scale sample,exhibiting good scale dissolving effect. According to the kinetic simulation,it was verified that the dissolving process of calcium carbonate by the descaling agent system conformed to the quasi-second-order kinetic model.

    • LIANG Junyi, ZOU Jincheng, LI Lin, ZHANG Xi, LIANG Bing

      2024,41(2):335-342, DOI: 10.19346/j.cnki.1000-4092.2024.02.021

      Abstract:

      In order to analyze the polymerization process of maleic anhydride(MA)and sodium allyl sulfonate(SAS),two variables were designed,such as neutralization degree and initiator dosage,while the formula and process remained basically unchanged. A series of MA/SAS samples were synthesized by changing one of the variables,and then were characterized by nuclear magnetic resonance spectrometer and gel permeation chromatograph. The results showed that the copolymerization activity of MA and SAS was good. When the neutralization degree did not exceed 100%(relative to the mole percentage of MA),a small amount of initiator (2.4 g sodium persulfate) would cause a high monomer conversion,but 6% —8% of the monomers remained unpolymerized. The type and quantity of remaining monomers were closely related to the neutralization degree and initiator dosage. MA was partially hydrolyzed into maleic acid in aqueous solution. Although the amount of maleic acid was relatively small,it could make a bimodal molecular weight distribution of the copolymer as a relatively poor polymerization activity. Adding alkali could neutralize maleic acid. When the neutralization degree did not exceed 100%,maleic acid mainly became a monosodium maleate with good polymerization activity,indirectly promoting the polymerization of MA monomers. When the neutralization degree was 200%,maleic acid mainly turned into disodium maleate,which had relatively poor polymerization activity and seriously hindered polymerization. When it was not neutralized or the neutralization degree was 100%,it took 7.0—7.2 g of initiator to convert all the monomers. At an appropriate neutralization degree(about 20%),a small amount of initiator(4.0—4.2 g)was needed. A more completely polymerized copolymer could be obtained,saving about 40% of the initiator dosage. The static scale inhibition performance of calcium carbonate,calcium phosphate,and calcium sulfate was studied using MA/SAS copolymers synthesized under optimum conditions. The copolymers showed excellent inhibition of calcium phosphate scale and calcium sulfate scale,as well as good inhibition of calcium carbonate scale. The corresponding maximum scale inhibition rates were 94.38%,100.00% and 59.03%,respectively.

    • CHEN Beier, YANG Li’an, LI Jiansha, LUO Xiangrong, PAN Qianhong, REN Xiaojuan

      2024,41(2):343-349, DOI: 10.19346/j.cnki.1000-4092.2024.02.022

      Abstract:

      Aiming at the wettability evaluation of fracturing oil displacement agents in low-permeability tight reservoirs,the error and uncertainty of the existing contact angle method were analyzed. An improved method for evaluating the wettability of fracturing oil displacement agents was proposed. The wettability tendency index,i.e.,the ratio of wetting contact angle between oil displacement agents and distilled water on the hydrophilic/lipophilic surfaces,was used to characterize the wettability change direction and degree of fracturing oil displacement agents. The results showed that there was some uncertainty in reflecting both the direction and ability of the oil displacement agent to change the reservoir wettability by the contact angle and the maximum value of the contact angle change. Hydrophilic surfaces were very stable and had small deviations in wetting contact angle,while lipophilic surfaces had large deviations in wetting contact angle. The relative average deviations of the wetting contact angles between distilled water and hydrophilic/lipophilic surfaces were 0.281% and 8.929%,respectively. In addition,the differences in the maximum change values of contact angles of some oil displacement agents on hydrophilic/lipophilic surfaces were not obvious. The wettability change degree of oil displacement agents could be better characterized by wetting tendency index. The uncertainty of wetting tendency index was much smaller than that of contact angle. The uncertainties of contact angle(wetting for 30 s)of 0.2% sulfonate oil displacement agents,polyoxyethylene ether oil displacement agents and fluorocarbon oil displacement agents on hydrophilic surfaces were 1.24,3.11 and 0.64,respectively,while their uncertainties of water wetting tendency index were 2.48×10-2,6.33×10-2 and 1.76 × 10-2,respectively. The water-wetting index of natural rock samples under the effect of seven fracturing oil displacement agents was measured by the Amott method. The order of this water-wetting index from largest to smallest was consistent with the order of water-wetting tendency index from smallest to largest measured by the contact angle method. The test results of both methods further confirmed the accuracy and superiority of wetting tendency index. This method was beneficial for quickly evaluating the ability of fracturing oil displacement agents to change reservoir wettability and for preferentially selecting fracturing oil displacement agents for low-permeability tight reservoirs.

    • ZHANG Yunbao, CHEN Danfeng, ZHANG Hong, LI Wentao, DU Ruofei, DONG Hongchao, DU Junhui

      2024,41(2):350-355, DOI: 10.19346/j.cnki.1000-4092.2024.02.023

      Abstract:

      Polymer microspheres drive conditioning are one of the main techniques to improve water drive effectiveness. The transportation in formation and effectively detection in extracted water of microspheres will directly affect the modulation drive. So the fluorescent carbon dots were introduced into the microsphere drive conditioner to play the role of tracer. The fluorescent core-shell microspheres drive conditioner formed from a mixture of core microsphere solution containing fluorescent carbon dots and shell layer aqueous solution. In order to reduce the interference of impurities in the extracted water after oil-water separation on the effective detection of core-shell fluorescent microspheres,the feasibility of the method was verified by firstly performing a linear fitting between the concentration of fluorescent microspheres and fluorescence intensity. Then the extracted water was adsorbed by silica gel. The practicability of silica gel adsorption was verified by comparing the fluorescence emission spectra of the extracted water before and after adsorption. Finally,the fluorescent microspheres prepared from the extracted water were adsorbed with silica gel,and then the standard curve of fluorescence intensity and microsphere concentration was plotted. The results showed that at the excitation wavelength of 347 nm,there was a good linear relationship between the mass concentration of fluorescent microspheres and the fluorescence intensity at the emission wavelength of 445 nm,with the correlation coefficient of determination (R2)of 0.9870. The fluorescence intensity of the water-driven extracted water was significantly reduced after silica gel treatment. The silica gel adsorption could effectively remove the impurities in extracted water. At the excitation wavelength of 347 nm,the fluorescence spectrometer slit of 10—20 nm,and the mass concentration of microspheres from 1 to 1200 mg/L,the mass concentration of fluorescent core-shell microspheres in aqueous dispersion (x) was positively and linearly related to the fluorescence emission peak at 462 nm(y). The fitted equation was y=2497.1042+3.1847x,with R2 of 0.9972,which had a high confidence level. The linear phase between the fluorescence intensity and the concentration of core-shell microspheres could meet the requirements of field detection. The method could provide a reference for the quantitative detection of fluorescent microsphere content in similar reservoirs.

    • YANG Zhongquan, CHENG Tingting, LUO Taotao, LI Jun, YANWende, HOU Jirui

      2024,41(2):356-366, DOI: 10.19346/j.cnki.1000-4092.2024.02.024

      Abstract:

      As conventional oil reservoirs enter the“double high”stage of high production and high water content,the availability of remaining reserves decreases and then the difficulty of stable oil production increases. To tap the remaining oil in reservoir for a long time,it is necessary to strengthen the characterization and understanding of the distribution of remaining oil. By combing the core analysis,one-dimensional core oil repulsion and microscopic oil repulsion experiments carried out at home and abroad for different reservoirs,and combining the techniques of laser confocal,nuclear magnetic resonance imaging,CT scanning imaging and fluorescence analysis,this article comprehensively summarized the research methods on the distribution of one- to threedimensional microscopic residual oils from qualitative to quantitative. The results showed that the oil-bearing thin section analysis was the basic experimental method to study the distribution of residual oil with high retention of the residual oil distribution state, which could truly reflect the characteristics of residual oil and was mature. The traditional core driving model was an indispensable experimental method for the study of the residual oil distribution law and the mechanism of improving recovery,which was the most reflective of the real reservoir situation. But it could only analyze the influence of different factors on the permeability effect from the macroscopic point of view. The real core visualisation model could effectively make up for the shortcomings of traditional core oil repulsion model. But the visualisation experimental device had limited resistance to high temperature and high pressure. Meanwhile,the production cost was high,and the image processing was not very clear. Microfluidic control model,as an emerging technology,had controllable parameters and high experimental reproducibility. At the same time,it could display the microdrive process and the flow of fluids visually under various oil repulsion modes,which could provide a new way of evaluating the effect of oil repulsion. However,there was still a certain gap between the simplified microscopic porous model and the results of actual displacement experiments. The imaging analysis technology mainly based on nuclear magnetic resonance imaging technology and X-ray CT imaging technology,with their respective advantages,combined with the real core experiments,had become an important means of effectively describing the characteristics of residual oil distribution from a microscopic perspective. This review provided important references for researchers to understand the existing research methods for remaining oil,and then provided theoretical support for the study of remaining oil distribution,efficient development,and improved oil recovery in different types of reservoirs.

    • ZHANG Zejun, WANG Zhansheng, ZHANG Hua, WANG Qingji

      2024,41(2):367-376, DOI: 10.19346/j.cnki.1000-4092.2024.02.025

      Abstract:

      Crude oil contains natural surfactants such as asphaltenes,resins,naphthenic acids,fatty acids,microcrystalline waxes, and interfacial active solid particles. During extraction,the shearing,compression and agitation within formation pores,wellbores, nozzles and pipeline valves,along with the addition of surfactants and water in oil displacement agents,as well as pump pressure and pipeline turbulence during collection and transportation,can easily form stable crude oil emulsions. Crude oil emulsions not only cause corrosion in pipelines and pumps and reduce pipeline transportation efficiency,but also lead to catalyst poisoning during downstream refining processes. Chemical demulsification,due to its high efficiency,rapid action,simple equipment requirements, and low energy consumption,is a commonly used method for the efficient separation of crude oil emulsions. Ionic liquids(ILs)are effective demulsifiers due to the advantages such as non-flammability,good thermal stability,recyclability,and low vapor pressure. By summarizing the characteristics of ILs and their current application as chemical demulsifiers,this paper discussed the demulsification mechanisms and factors influencing demulsification performance. It identified issues with the practical application of ILs demulsifiers,and then suggested future research directions. ILs were suitable for demulsification under harsh conditions such as high salinity,high temperature,and high viscosity(e.g. extra-heavy oil). Demulsification mechanisms included adsorption, replacement and ion exchange. Factors affecting demulsification effect included the type and concentration of ILs,relative molecular mass,salinity,temperature,and emulsion type. By selecting appropriate ILs and their dosages,and determining optimum treatment conditions,demulsification efficiency could be enhanced. Although there were still significant challenges and key issues preventing large-scale application of ILs demulsifiers,the development of low-toxicity or non-toxic,low-cost, low-viscosity ILs and their use in conjunction with nanoparticles,and polymer ILs remained highly significant.

    • LIN Zhangbi, YANG Mingjiao

      2024,41(2):377-380, DOI: 10.19346/j.cnki.1000-4092.2024.02.026

      Abstract:

      The new national standard GB/T 7713.2—2022“Presentation of academic papers”partially replaces GB/T7713—1987 “Presentation of scientific and technical reports,dissertations and scientific papers”,which has been implemented on July 1,2023. Good learning and implementation of the new national standard is of great significance to the standardization of academic papers preparation and publication,so as to facilitate the retrieval and dissemination of academic papers and promote the exchange and use of academic achievements. When learning“Presentation of academic papers”,it should pay attention to the difference between requirements,recommendations,permits and statements. The auxiliary verbs used in each clause should be distinguished. Combined with the characteristics of oil and gas industry and the actual editing work,this paper analyzed the common non-standard problems in title,abstract,keyword,text part,quantity and unit,table,number and mathematical formula. Authors and editors should pay more attention to the standardization,which helped to improve the standardization level of academic paper writing and editing.

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    • Study on a Noval Solid-free Polymer Gel System for Grouting in Luohe Formation Sandstone

      LI Jiaming, ZHAO Guang, DAI Caili

      Abstract:

      The frequent water gushing in sandstone mining strata of Luohe Formation has seriously affected the safety production of the mine. The traditional grouting systems are faced with the problems of serious percolation effect and uncontrollable gelation performance, which is difficult to achieve effective regulation of fissure water. In this work, the microscopic characteristics of sandstone pores are clarified by analyzing the mineral composition and microscopic morphology of typical core samples. A solid-free polymer gel system with low cost and excellent stability is constructed for grouting, and the grouting performance evaluation is further carried out. The results show that the small pore diameter and poor connectivity are the geological reasons for the difficulty of smooth injection and long-distance migration of the traditional grouting systems. The noval polymer gel system with low cost, solid-free and easy injection for grouting can achieve gelation within 48h and has excellent long-term aging stability. The system has good injectivity and the pressure attenuation is not obvious after continuous flooding, with the plugging ratio remaining above 80 %. The system increases the seepage resistance and blocks the subsequent fluid by occupying the large channel or fracture space, which realizes the effective plugging of the water layer. The results of this work provide new ideas for the grouting and water plugging in Luohe Formation sandstone.

      • 1
    • Construction and performance of high stability supercritical CO2 Foam for channeling blocking during CO2 flooding

      LI Weitao

      Abstract:

      Aiming at the problems of low sweep efficiency of CO2 flooding and poor performance of conventional foam profile control ability, a high stability supercritical CO2 foam system composed of amphoteric surfactant HSD and modified SiO2 nanoparticles is constructed. Low permeability reservoirs in Shengli Oilfield are buried deep and have high temperature.The system showed good high-temperature resistance. At 120 ℃, the concentration of 0.5% nanoparticles increased the half-life of foam from 17 minutes to 40 minutes, and the stability was improved by nearly 2.5 times. The increase of reservoir pressure can increase both bubble volume and foam stability. Based on the power law model, the effect of nanoparticles on the rheological properties of supercritical CO2 foam system was studied. The results showed that the apparent viscosity of the system increased with the increase of the concentration of nanoparticles under the same shear rate, and the consistency coefficient increased from 0.073 to 1.22. The change rule of apparent viscosity of supercritical CO2 foam in porous media is simulated through core displacement experiment. The steady-state apparent viscosity of foam in porous media increases with the increase of nanoparticles. The foam of supercritical CO2 foam is stacked and discharged in "granular" shape. The size of foam is about 10 ~ 20um. Finally, the mechanism of nano particles enhancing the stability of CO2 foam was confirmed through experiments. The hydrophilic nano silica had interfacial activity due to the adsorption of surfactant molecules, which was adsorbed from aqueous solution to the gas-liquid interface, thus improving the stability of foam.

      • 1
    • Recent progress in synthesis of oligomeric cationic surfactants

      QIAO Fulin

      Abstract:

      In recent years, oligomeric surfactants, as a novel class of surfactant with superior efficiency at very low concentration, have shown promising applications in the fields of enhance oil recovery, pharmaceuticals, corrosion inhibitors, and so on. Oligomeric surfactants are composed of two or more amphiphilic moieties, which are chemically linked by a spacer group, and they bridge the gap between monomeric surfactants and polymeric surfactants. With the help of the spacer group, the spatial distance of multiple amphiphilic moieties becomes closer, contributing to the stronger aggregation ability of the oligomeric surfactants. Meanwhile, the structures of the spacer group and the topological configuration are more diversified, resulting in multifarious transition processes of molecular configuration and aggregation morphology. These characteristics make them show unique advantages as highly-efficient oilfield chemicals and stimuli-responsive soft materials, but the difficult synthesis processes have been identified as the bottleneck of their systematic investigations. In this review, the synthesis methods of linear, star-like and ring-type oligomeric cationic surfactants, which are classified by the spatial topological structure, are summarized in detail, and a brief review of future perspectives on the oligomeric surfactants are also discussed.

      • 1
    • Research status and prospect of lost circulation formation drilling fluid plugging materials

      LIU Jing, MA Cheng

      Abstract:

      Lost circulation is the main technical problem that restricts the improvement of the quality and efficiency of oil and gas drilling engineering. Improving the success rate of one-time plugging is an urgent need to ensure "safe, efficient and economic" drilling in global oilfields. Aiming at the study of drilling fluid leakage mechanism, the drilling fluid leakage mechanism is systematically summarized. Through the research of domestic and foreign scholars in recent years, plugging materials such as bridging, high water loss and curable have been developed. The properties and interaction mechanism of various plugging materials such as bridging, high water loss, curing, polymer gel, etc. are systematically introduced. The existing problems of plugging materials are clarified, and the future development direction of plugging materials is proposed.

      • 1
    • Low interfacial tension small molecule oil displacement agent to improve oil recovery in low permeability reservoir

      MENG Wenyu, TANG Shanfa

      Abstract:

      Poor injection of low permeability reservoirs, low efficiency of wash oil, water flooding can effectively improve recovery factor and so on question, this paper proposes a low interfacial tension of small molecular oil displacement agent (LST) new technology improve the recovery factor of low permeability reservoir, the interfacial activities of evaluation of the oil displacement agent, viscosity, emulsification, wettability and its reservoir environment adaptability and oil displacement effect. The results show that the oil displacement agent has good interfacial activity and viscosity. When the mass fraction is 0.4%, the oil-water interfacial tension is as low as 0.012mN/m-1, and the viscosity is close to that of the reservoir oil (3.4mPa?s). The oil displacement agent also has good oil-water emulsification ability, little influence of static adsorption on interfacial activity and viscosity enhancement, and good hydrophilic wettability, which can effectively improve water recovery efficiency at low dose or cost. By injecting 0.4%LST(0.4PV), the water flooding recovery of homogeneous core (50mD) can be increased by 11.210%, and the comprehensive water

      • 1
    • Performance Evaluation of Gel Plugging System for High Pressure Water Injection Well

      WANG Wanfei, FU Hong

      Abstract:

      In order to meet the strength, gelation time and gel breaking performance requirements of gel plugging system for high pressure water injection wells under pressure, a temperature-resistant and salt-resistant gel plugging system was prepared by using AM / AMPS ( acrylamide / 2-acrylamide-2-methylpropanesulfonic acid ) as binary polymer system and Smel30 (Trihy-droxymethyl compound) as crosslinking agent. The effects of temperature, inorganic salt, simulated oil content and shear time on gelation time and gel strength of the gel system were studied. At the same time, the effect of dosage of gel breaker sodium persulfate on gel breaking effect of gel system was studied. The results showed that the gelation time was shortened with the increase of temperature. When the temperature was 60 °C, the gelation strength was 73.5Pa and the gelation time was 7 h. The addition of inorganic salts reduced the distance between polymer chains, shortened the gelation time, and slightly increased the gel strength. The influence of three salts on gelation time and gel strength was NaCl < MgCl2 < CaCl2; the system has strong resistance to oil pollution; after shearing for 60 min, the gel strength can still maintain more than 81 %, which has strong shear resistance. The gel system did not dehydrate after 15 days of aging and still had strong gel strength; sodium persulfate can be used as a gel breaker with high efficiency and low cost, and the apparent viscosity of the residue is less than 64.4 mPa·s.

      • 1
    • Study of Surface-active Injection Enhancement System for Reservoirs with Low Permeability and High Salinity

      ZHANG Guoqing, GONG Zhuoting, YI Xiao, WANG Zhengliang, ZHENG Yancheng

      Abstract:

      Low permeability reservoirs have the characteristics of small pore throat radius, low permeability and water absorption ability. In order to improve the recovery efficiency of chemical flooding, a compounded system of alcohol ether sulfonate and betaine surfactant was established. The alcohol ether sulfonate DP6E6S characterized by 1H NMR was obtained by the introduction of propylene oxide and ethylene oxide into dodecanol and sulfonation. It was compounded with cetamide betaine PNC to evaluate surface properties, interaction properties, interface properties, wettability and emulsification properties of the complex system and the injection enhancement was obtained by core flooding experiments. It is showed that PNC and DP6E6S have strong synergistic effect of reducing critical micelle concentration (cmc) and surface tension effectively. The interfacial tension of the compound system decreases with the increase of salinity, especially n(PNC): n(DP6E6S) =2:3 and 1:1 which can reach 10-3 mN?m-1 in a wide range of salinity (>5%). The mole ratio of n(PNC): n(DP6E6S) =2:3 and 1:1 formed the more volume phase emulsion showed the best dissolution effect. The particle size of emulsion droplets first decreases and then increases with the increase of salinity. The interfacial tension of the compounded system is still low after core adsorption showed good adsorption resistance. The mole ratio of n(PNC): n(DP6E6S) =1:1 with larger wetting angle and smaller capillary force is conducive to depressurization and injection enhancement. The depressurization rate of the two optimized systems can reach 28.9% and 23.9%, respectively, indicating that low interfacial tension and high wetting angle are conducive to depressurization and injection enhancement of low permeability reservoirs.

      • 1
    • Mechanical strength of polyacrylamide composite hydrogel reinforced by nanocrystalline cellulose

      MA Yanqi, LIN Meiqin

      Abstract:

      The strength of gels determines its use and high mechanical strength gels have been applied in many fields. In order to enhance the strength of acrylamide (AM) gels, nanocrystalline cellulose (NCC) was used to prepare the AM/NCC composite hydrogel.The effects of NCC on the tensile properties, compressive properties, adhesion properties and viscoelastic properties of AM/NCC composite hydrogels were investigated by using texture analyzer and rheometer, and the microstructure of the composite hydrogels was observed by scanning electron microscope (SEM).The results showed that the tensile strength, compressive stress, adhesion and viscoelasticity of AM/NCC composite hydrogel were significantly higher than those without NCC. When the mass ratio of AM to NCC was 5:3, the tensile strength, compressive stress and viscoelasticity of the composite hydrogel reached the maximum. The toughness of AM/NCC composite hydrogel was significantly enhanced, and the tensile stress and adhesion force were nearly 4 times higher than those of AM gel.The strength of AM/NCC composite hydrogel is related to its microstructure, and the network structure of AM/NCC composite hydrogel is significantly denser than that of AM gel.

      • 1
    • Construction and Performance Evaluation of Emulsification-Stripping Dual Effect System for Heavy Oil

      HU Junjie, ZHANG Guicai

      Abstract:

      There are some problems in the development of the heavy oil reservoir in Shengli Oilfield, such as high viscosity and poor fluidity of crude oil, which the recovery efficiency of the water drive is not ideal. Therefore, the emulsification-stripping system was constructed with the instability coefficient of emulsification, the shrinkage rate of oil film and the minimum emulsifying speed as indexes. The emulsification and stripping ability of different surfactants for heavy oil were evaluated. The compound system of 0.3wt%CBT/ASC(m(CBT):m(ASC)=3:2) was optimized. The displacement effect of the emulsification-stripping system was evaluated by the laboratory sand-filling flow experiment. The mechanism of its action was studied by a microcosmic model. The results showed that CBT had excellent emulsification performance and significantly reduced interfacial tension for heavy oil, and ASC had good stripping ability for heavy oil. The compound system has excellent emulsification-stripping function, and the enhanced oil recovery rate can reach 14.18%. The research results have important guiding significance for efficient development of heavy oil reservoir.

      • 1
    • Screening and evaluation of cheap nutrient system for sandstone reservoir in well block LQ, Xinjiang

      WANG Hongbo, MA Ting

      Abstract:

      According to the nutritional requirements of the main oil recovery functional bacteria in the sandstone reservoir of LQ well block, the optimal carbon source, nitrogen source and phosphorus source were selected through single factor experiment, and the concentration of each component was preliminarily determined, on this basis, the significant influence factors of each component were analyzed by Plackett-Burman experiment and factor removal experiment, and the concentration of each component was determined, finally, response surface test was used to determine the concentration of each component, the final concentration was obtained by further optimizing each component according to the factors. The results showed that the selected nutrient system had good emulsifying effect, the main oil recovery function gene hydrocarbon oxidation gene reached 107copies/ml, and the physical model oil displacement experiment improves oil recovered by 11.65%. This study provides a good technical support for the field test of microbial flooding in well block LQ.

      • 1
    • Research progress of drag reducers for fracturing and its drag reduction mechanism

      SI Xiaodong, LI Mingzhong

      Abstract:

      Drag reducer is the key additive of fracturing fluid for unconventional reservoir reconstruction, such as tight sandstone and shale, and its performance will directly influence on the fracturing operation effect. The advantages,disadvantages and application of different drag reducers were analyzed. The turbulent drag reduction and drag reduction failure mechanism of drag reducers were emphatically described. The research progress of nanomaterials in fracturing drag reduction was summarized. This paper points out that in unconventional reservoir fracturing environment such as high temperature, high shear and complex medium, the new type of multi-functional composite drag reducers with the advantages of stability, high efficient drag reduction, low reservoir damage, strong sand carrying capacity, easy flowback and easy recycling will be an important research direction in future.

      • 1
    • Effect of autogenous heat system on fracturing fluid gel breaking performance

      SHEN Xiulun

      Abstract:

      Aiming at the problems of incomplete fracturing and low flowback ability in low-temperature shallow oil and gas wells, the heat generation of three different autogenous heat generation systems, including nitrite and ammonium salt, chromium trioxide, glucose, and hydrogen peroxide, was investigated. And the impact on the fracture gel breaking performance. The experimental results show that the heat generation of the heat generating system of nitrite and ammonium salt is the highest, and the temperature can reach above 80℃. In addition, the order of addition of three different heat generating systems and breakers is also determined in the experiment to make fracturing The liquid gel breaking effect is the best. Among them, the order of adding the heat generating system of glucose and chromium trioxide and the heat generating system of nitrite and ammonium salt is to add the heat generating system first, then add the APS breaker and hydrogen peroxide heat generating system. The order of addition is to add both autogenous heat system and APS breaker at the same time; finally, it is concluded that the autogenous heat system of nitrite and ammonium salt is the best additive for fracturing fluid gel breaking system, which can reduce the viscosity of fracturing fluid to 6 Below mPa.s, the best glue breaking performance.

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    • Development and application of double-protection weighting agent for drill-in fluidZhuo Lvyan You Zhiliang Zhao Cheng

      ZHUO Lvyan

      Abstract:

      The arsenic content of barite supplied in China mostly exceeds the filter value of Second type of construction land in‘GB 36600-2018 Soil environmental quality Risk control stardard of soil contamination of development land’. Iron ore powder and ilmenite powder are commonly used as weighting agents, but they wear drilling tools seriously, which affects the electrical measurement results, and the chroma of drilling fluid is not up to standard after use, so they are rarely used now. Calcium carbonate is also a common weighting agent, due to its low viscosity, the viscosity effect is obvious, which has an impact on drilling. In view of the shortcomings of the environmental protection performance and application performance of the weighting agent, choose calcium carbonate weighting agent,adding barite into it proportionally,after surface coating modification, dry activation treatment and other production processes, The viscosity effect and the arsenic content is reduced.At the same time, it is beneficial to the hydrocarbon reservoir protection characteristics of calcium carbonate weighting agents . Innovation has formed a double-protection weighting agent that protects oil and gas reservoirs and the environment.The technology has been applied to 10 wells,all wells were drilled safely. Compared with the average value of adjacent wells, the penetration rate increased by 10%, the average hole diameter expansion rate decreased by 1.8%, the average oil production per meter of single well increased by 0.60t, and the arsenic content of mud cake reached the standard screening value (less than 60mg/Kg).

      • 1
    • Optimization of synthesis conditions and evaluation of indoor oil displacement effect of a supercritical carbon dioxide thickener

      Fu Hong

      Abstract:

      carbon dioxide flooding (CO2) is an effective means to further develop old oilfields with high water cuts and improve oil recovery based on tertiary oil recovery. Aiming at the gas channeling problem caused by the large viscosity difference between carbon dioxide and crude oil, a supercritical carbon dioxide thickener agent P-1 that can be applied to oil flooding was prepared. Through orthogonal experimental analysis, it is concluded that the amount of initiator has the greatest influence on the molecular weight distribution of the reaction, the optimal molar ratio of the synthetic monomer is 4:1:1, the molecular weight distribution is 1.12, and the yield is 88%. The synthesized product under optimal conditions was characterized by infrared characterization, and the characteristic absorption peaks matched the product. The evaluation results show that the saturation solubility of P-1 in supercritical carbon dioxide is 2.30%, and the minimum miscible pressure is 7.77Mpa.The thickener with a monomer concentration of 0.2% increased the viscosity of supercritical carbon dioxide by 42 times at 30Mpa, 50℃, the viscosity was 1.1675mPa.s, and the viscosity retention rate was 46.41%, while the temperature was raised to 110℃. Simulating the formation environment (15MPa), adding the thickening agent P-1 with a mass concentration of 0.2% can effectively improve the oil displacement effect of supercritical carbon dioxide flooding, and the lower the permeability, the more significant the extraction effect. In the same core, the total recovery degree of supercritical carbon dioxide flooding is more than 10% higher than that of supercritical carbon dioxide flooding after water flooding.

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    • Experimental on lubricating oil for drilling fluid based on aging oil

      Jiaxue Li

      Abstract:

      Aging oil, a by-product of oil field surface production, has complex interface characteristics and is difficult to be dehydrated. Using aging oil to develop drilling fluid lubricant can make use of its emulsifying stability and avoid the problem of removing mud, sand and water from aging oil.Through a large number of experiments, the key emulsifier of drilling fluid lubricant based on aging oil is OP-4, the wetting agent is ABS, and the stabilizer is Na-CMC. The experiment determines that the best formula of the drilling fluid lubricant is 100ml drilling fluid + 3ml aging oil + 1.5g OP-4 + 0.15g ABS + 0.015gNa-CMC. Through the benchmarking national standard experiment, the developed drilling fluid lubricant based on aging oil meets the requirements for lubricants in the standard. Using aged oil as base oil to develop drilling fluid lubricant is a feasible resource treatment scheme for aged oil, which has great application value.

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    • PREPARATION OF HIGHLY POROUS NI-MO CATALYST BASED ON γ-AL2O3 AND ITS CATALYTIC EFFECT ON ULTRA-HEAVY OIL VISCOSITY REDUCTION

      Yuan Chengdong

      Abstract:

      The ultra-heavy oil reservoir in Tahe Oilfield is currently producing by mixing light oils with ultra-heavy oils in wellbore to reduce viscosity. However, the high ratio of needed light oils and abnormal fluid production caused by uneven mixing make the production low efficient and high cost. To solve this challenge, in this work, we proposed the technology of catalytic ex-situ upgrading for viscosity reduction + reinjection of upgraded oil into wellbore to save the amount of injected light oils and improve the recovery efficiency. To develop a catalyst system that can effectively reduce the viscosity of the ultra-heavy oil and achieve high-level ex-situ upgrading, a Ni-Mo catalyst with high porosity based on γ-Al2O3 carrier was developed and its catalytic effect on the ex-situ upgrading and viscosity reduction was evaluated. The results show that the developed Ni-Mo catalyst can reduce the viscosity of ultra-heavy oil at 50 ℃ from 28200 mPa.s to 298 mPa.s. The viscosity is reduced by nearly 100 times, and the viscosity reduction rate is 98.94%. The density is decreased from 1.007 g/ml to 0.8724 g/ml. At the same time, the content of saturates is significantly increased, and the content of resins and asphaltenes was greatly decreased. The developed catalyst system shows an excellent ex-situ catalytic upgrading effect for extra-heavy oil and has a great potential for field application.

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    • Evaluation of inhibition effect of ionic liquid on asphaltene precipitation in crude oil under high temperature and pressure

      CAO Pengfu

      Abstract:

      ionic liquids have great potential to prevent asphaltene precipitation in reservoir development, but the inhibition effect of ionic liquids under high temperature and high pressure is not clear. Based on the calibration of the relationship between asphaltene content and absorbance in organic solvents, the inhibitory effects of two ionic liquids [bmim] Cl and [bmim] BR and two common commercial inhibitors on asphaltene precipitation in crude oil were evaluated by spectrophotometry, and the determination experiments of asphaltene precipitation at high temperature and high pressure were carried out with the best inhibitor and ratio concentration, The effects of ionic liquid on the initial pressure of asphaltene precipitation (AOP) and the size of asphaltene aggregate in formation crude oil and CO2 injected formation crude oil were studied. The experimental results show that the inhibitory effect of ionic liquid [bmim] BR on asphaltene precipitation is much higher than ionic liquid [bmim] Cl and two other commercial inhibitors, and the optimal concentration is 600 ppm. The AOP of pure formation crude oil is 28.7mpa. When [bmim] BR is added, the AOP decreases by 21.6%. When isopropanol is added to ionic liquid, the AOP decreases by 29.6%. The AOP of formation crude oil saturated with 30mol% CO2 is 31.6mpa, which is 10.1% higher than that of pure formation crude oil. When isopropanol and ionic liquid mixed solvent are added, the AOP decreases by 44.3%. Isopropanol can produce ternary interaction with [bmim] BR and CO2, improve the activity of [bmim] BR, greatly reduce the AOP of saturated CO2 crude oil, slow down the growth rate of asphaltene particle size, reduce the deposition depth and blockage degree of asphaltene in the wellbore, and introduce asphaltene deposition into more controllable nodes, which has broad application prospects. The results obtained provide a reference for the prevention and control of asphaltene deposition and rational and efficient development.

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    • Oil contaminated soil treatment new technology-the applicability of the plant type microbial fuel cell research

      gaojie

      Abstract:

      Oil enters the soil during refining, storage, transportation and use, causing pollution. Oil pollutants are highly harmful and difficult to deal with. Plant Microbial Fuel Cell (PMFC) is proposed to solve this problem. The PMFC was constructed with oil-contaminated soil as anode sludge. By detecting the output voltage, power density, apparent internal resistance and oil removal rate, the battery plants and electrode materials were optimized, and the optimized PMFC was used to explore the oil concentration applicability and optimum scope of application. The results showed that the green dill in plants could not survive in the anaerobic environment of PMFC, while the electricity production and degradation properties of white crane taro-PMFC were better than those of Lentinus edodes-PMFC; Compared with carbon sponge-PMFC, the power generation performance and degradation performance of carbon felt-PMFC in electrode materials are significantly improved; PMFC with white crane taro as battery plant and carbon felt as electrode material is suitable for any oil concentration, and with the increase of oil concentration, the power generation performance and degradation performance of PMFC show a trend of increasing first and then decreasing. So there is an optimal oil concentration range of 5-10g/kg. PMFC technology provides a new idea for oil-contaminated soil treatment, which can effectively deal with soil pollution problems while generating electricity and achieve a win-win situation.

      • 1
    • Study on low temperature degradation of HPAM gel by activation of persulfate

      ZHU Jianjun, WANG Yefei

      Abstract:

      Temperature is a key factor limiting the degradation of polymer gel. Aiming at the blockage caused by polymer gel in low temperature reservoirs, the system of TA activated persulfate was proposed to use as a plugging remover to degrade polymer gel in this work. First, the quenching experiment and the radical test were used to determine the mechanism to degrade the polymer; the second was to study the effect of persulfate concentration, TA concentration, temperature and anions in formation water on the degradation, and the optimal reaction concentration was selected according to the change of polymer gel’s degradation efficiency and the corrosion with the concentration; Finally, the degradation effect of the system was compared with the conventional polymer plugging removers. The results showed that TA activated persulfate can rapidly degrade the polymer gel at 35 ℃, and the superoxide anion radicals are the main active radicals in degradation reaction. Compared with other polymer plugging removers, the said system of TA activated persulfate could rapidly degrade polymer gel with mild corrosion in the low temperature reservoir.

      • 1
    • Study on improving anti-pollution performance of shale gas well cementing cement slurry with surfactant

      HE Guanxi

      Abstract:

      When shale gas reservoir is developed by horizontal wells, due to casing eccentricity and irregular well diameter, the displacement efficiency of oil-based drilling fluid is usually low. It is inevitable that some oil-based drilling fluid will be mixed into cementing cement slurry and pollute the performance of cement slurry. Therefore, in order to improve the anti-pollution ability of shale gas cementing cement slurry, the indoor research on improving the anti-pollution performance of shale gas well cementing cement slurry with surfactant AFSG-1 was carried out with on-site oil-based drilling fluid and cementing cement slurry as the research object. The results show that the addition of on-site oil-based drilling fluid will seriously affect the fluidity, thickening time and slurry water mud properties of cementing cement slurry. The greater the proportion of oil-based drilling fluid, the more serious the pollution is; With the increasing amount of surfactant AFSG-1 in the cementing cement slurry, the anti-pollution ability of the cement slurry is gradually enhanced. When the mass concentration of surfactant AFSG-1 in the cementing cement slurry reaches 2%, and then 20% oil-based drilling fluid is added, the fluidity, thickening time and cement stone properties of the slurry are significantly improved compared with those without surfactant. In addition, the effect of surfactant afsg-1 on improving the oil-based drilling fluid pollution resistance of cementing cement slurry is significantly better than that of other commonly used surfactants. The results show that surfactant AFSG-1 can effectively improve the anti oil-based drilling fluid pollution ability of shale gas cementing cement slurry, improve cementing quality and ensure cementing safety.

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    • Corrosion mechanism and performance evaluation of inorganic blockages by neutral chelating system

      Qu Ming, Hou Jirui

      Abstract:

      Acidizing plugging removal technology is often used to solve the problems of reservoir pollution and lack of liquid supply caused by long-term development of carbonate reservoirs. Due to conventional acidizing technology is special for carbonate reservoir, the conventional acidification technology is prone to water lock, corrosion of pipe string and wellbore scaling in the production process, leading to reservoir damage and reducing reservoir productivity. Therefore, this paper developed a neutral chelating system to remove inorganic plugging without backflow and secondary damage to the formation. Composing of chelating agent EDTA and corrosion inhibitor PAA, and a small amount of stabilizer Na2SO3 was added. It was prepared by deionized water fusion filtration, dehydration grinding and grinding at 120℃ and roasting activation at 500℃. The experimental results show that the system has good corrosion ability for inorganic plug such as Ca2+、Mg2+ ion, the corrosion rate is up to 95% within 24h at normal temperature. The corrosion rate of N80 steel is 4.45g/m2·h after 12h at 90℃. The average dissolution rate of natural carbonate cores can achieve more than 70%. Therefore, neutral chelation plugging removal system has a good potential for field application.

      • 1
    • Viscosity Prediction Model for Water-in-Oil Emulsion Based on Quantitative Characterization of Crude Oil Physical Properties

      LUO Haijun, WANG Zhihua

      Abstract:

      Eight kinds of crude oils with different physical properties were used to prepare water-in-oil (W/O) emulsions. The viscosity characteristics of the W/O emulsions were measured by rheometer. The effects of temperature, water cut of emulsion and shear rate on the apparent viscosity of W/O emulsions were studied. The results show that the apparent viscosity of the W/O emulsion decreases with the increase of temperature, increases with the increase of water cut, and decreases with the increase of shear rate, showing the property of shear thinning. The power law model was used to describe the rheological properties of W/O emulsion, i.e, . With the increase of water cut of emulsion, the consistency coefficient K of W/O emulsion increased gradually, while the rheological property index n decreased gradually. With the increase of temperature, the consistency coefficient K decreased gradually, while the rheological property index n increased gradually. Based on the experimental data and quantitative characterization of crude oil physical properties, a viscosity prediction model for W/O emulsion was established which could be applied to different crude oil and different shear conditions. The prediction deviation of the model shows that the average relative deviation between the calculated viscosity value and the measured viscosity value is 8.1%.

      • 1
    • Development and field application of anti-returning and plugging agents

      Zeng Guang, Wan Xiumei

      Abstract:

      Aiming at the characteristics of shale gas plugging in Sichuan-Chongqing block, easy to blow back and high requirements for pressure, this paper developed a kind of ARP anti-return leakage plugging agent based on high softening point resin. It has the ability of deformation, cementation and curing. It can be used in combination with bridge plugging particles to cement and solidify with plugging agent particles in formation cracks to improve pressure bearing capacity and anti-return ability. The laboratory evaluated the dispersibility of the ARP plugging agent in the field oil-based drilling fluid and the bonding strength with the field leakage plugging agent, and tested the pressure bearing capacity and anti-return ability after the cementation was cured. According to the needs of field application, the density of ARP anti-return leakage plugging agent is determined to be 1.8g/cm3, the particle size is 0.5-2mm, and the optimal ratio is formed with the field plugging agent. That is, ARP anti-return leakage plugging agent accounts for 25 parts, and on-site leakage plugging agent accounts for 75 parts, and its bonding strength can reach 7.8MPa. When plugging 2-3mm natural cracks, the positive pressure can reach 8MPa, and the anti-reflection ability can reach 3.3MPa. At the same time, the on-site construction process is designed according to the material characteristics, and a good on-site application effect is achieved.

      • 1
    • The corrosion inhibition performance and mechanism analysis of phenyl and benzoyl thiourea in hydrochloric acid

      Yu Yi

      Abstract:

      The inhibition performance and mechanism of two thiourea-based derivatives, phenylthiourea (PHTU) and benzoylthiourea (BOTU) for 20# steel in 15% HCl solution were investigated by corrosion weight loss experiments, scanning electron microscope (SEM), and quantum chemical calculations. The results indicated that both PHTU and BOTU showed good inhibition performance for 20# steel in 15% HCl solution, and the corrosion inhibition rate could reach more than 83% at 2 mmol/L. The adsorption of PHTU and BOTU on the steel surface was in accordance with the Langmuir adsorption model, and the adsorption model was a mixed physical and chemical adsorption. Quantum chemical calculations results showed that the reactive sites in the corrosion inhibitor molecule were mainly distributed in the C=S double bond, C-N bond and the C=O double bond. The N atoms in the corrosion inhibitor can form physical adsorption with the steel surface through electrostatic gravity after being protonated by the acid. The high electron cloud density of C=S bond, C=O bond and phenyl group can provide electrons to form chemisorption with the empty d orbitals of iron atoms through coordinate and feedback bonds, which can then be stably adsorbed on the metal surface to form a protective film and inhibit the corrosion process.

      • 1
    • Development and Function Mechanism of High Temperature Resistance Intercalation Adsorption Inhibitor

      Wang Xiao-Jun

      Abstract:

      High temperature resistance intercalation adsorption inhibitor has been developed for ?reducing wellbore instability caused by which conventional inhibitors could not controll effectively hydration of clay surface, There are a lot of strong adsorption groups and hydrophobic groups in the molecular structure of the new inhibitor, which was low molecular weight, non-toxic environmental protection and good thermal stability. The analysis of inhibition mechanism showed that, the new inhibitor,the electrostatic repulsion and short-range repulsion of surface hydration of clay can be effectively reduced by the combination of strong adsorption group and exchange of hydrated sodium ions.And by changing the surface tension and wettability of clay, the self-imbibition capacity and specific hydrophilicity of shale can be controlled, and the invasion of water phase can be reduced. Meanwhile.?the new inhibitor had strong adsorption and anti-desorption ability, could adsorb on the clay surface for a long time, improved the hydrophobicity of the clay surface, and reduced the invasion of free water. Laboratory evaluation experiments showed that the new inhibitor had good properties of inhibiting mud production, controlling clay hydration expansion and preventing mud shale collapse, which was beneficial to the stability of rheological property and borehole wall of water-based drilling fluid, it had a good application prospect.

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    • Laboratory study on solid-free constant rheological drilling fluid with reservoir protection for deep-water drilling

      Chen Liang, You Fu-chang.

      Abstract:

      In the drilling process of deep-water oil and gas fields, due to the low temperature near the bottom mud line, it was easy to lead to the thickening, paste plugging, slurry running and other problems of drilling fluid. The thermosensitive thickening copolymer ASSN was prepared with acrylamide, N-vinyl caprolactam, diethylbenzene and sodium allyl sulfonate as raw materials. ASSN was combined with fenugreek gum , which had strong salt resistance and significant cutting effect, to form a flow pattern regulator with low temperature constant rheological properties, and formed a set of solid-free constant rheological drilling fluid with reservoir protection for deep-water drilling with other treatment agents. 0.5%ASSN+0.3% fenugreek gum as flow pattern regulator played a good role in regulating the rheological properties of drilling fluid at low temperature. Its low temperature control ability of drilling fluid was less affected by different weighting agents, and it had good compatibility with other drilling fluid treatment agents, so that the FLAPI of drilling fluid was only 5.2mL. And it had good resistance to contaminated soil, field drilling cuttings, salt and seawater intrusion and excellent reservoir protection (recovery value of field core permeability was greater than 95%).

      • 1
    • Synthesis and Performance Evaluation of an Amphoteric Polymer Viscosity Reducer

      ZHANG Cheng, DUAN Ming

      Abstract:

      In this paper, acrylic acid (AA), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), and methacryloxyethyl trimethylammonium chloride (DMC) wereSusedSasSmonomers, based on the aqueous solution explosion polymerization process, a low molecular weight zwitterionic polymer viscosity reducer for drilling fluids was synthesized by using environmentally friendly tetramethylthiuram disulfide (TMTD) instead of sulfhydryl compound as the chain transfer agent. Taking the room temperature viscosity reduction rate as the evaluation index, the optimum synthesis conditions of the viscosity reducer have been determined: the monomer concentration was 55 wt%, the addition of TMTD was 0.75 wt%, the addition of oxidation-reduction initiator was 3 wt% of the monomer concentration, the neutralization of (AA+AMPS) was 50%, the addition of AMPS was 5.5 wt%, and the addition of DMC was 4.5 wt%. Under this condition, the number average molecular weight of the synthesized zwitterionic polymer viscosity reducer is 914 g/mol, and its viscosity reduction rate in the fresh water base slurry is 91.53%, and it has good temperature resistance, which can meet the temperature resistance requirement of 180 ℃. This research provides a green and environmentally friendly option for the synthesis of low molecular weight zwitterionic viscosity reducer.

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    • Effects of CO2 on the Aggregation Behaviorof Asphaltene Molecules in Heavy Oil

      JIANG Huixin, WANG Chuangye

      Abstract:

      The aggregation behavior of asphaltenes significantly affects the viscosity of heavy oil. Studying the aggregation behavior of CO2 on asphaltenes in heavy oil can further analyze the mechanism of CO2 displacement. Under different CO2 pressures and conditions, CO2 dissolution experiments were carried out on heavy oil and heavy oil added with benzene and ethanol as CO2 solubilizers. After separating the four components, CO2-treated asphaltenes were obtained. X-ray diffractometer, scanning electron microscope, transmission electron microscope and other analytical instruments were used to characterize the interlayer spacing, surface morphology and microstructure of asphaltene aggregates extracted under different experimental conditions, and the effect of CO2 on asphaltenes in heavy oil was analyzed. Influence mechanism of aggregation behavior. The results show that the dissolution of CO2 in heavy oil leads to an increase in the interlayer spacing of asphaltene aggregation stacking, which slows down the aggregation behavior of asphaltene molecules, thereby reducing the viscosity of heavy oil.

      • 1
    • Research progress and prospects of lubricants in water-based drilling fluid

      WANG Kai, LI Xiaoming

      Abstract:

      A great number of researches about eco-friendly and high-performance lubricant have been conducted to improve the lubrication of water based drilling fluids, solving the high friction of long horizontal section of horizontal wells and promoting the development of drilling technology for horizontal well. In this paper, the domestic and international research progress of lubricant for water based drilling fluids has been reviewed including the lubricants from alcohol ether, alkyl glycoside, modified vegetable oils, mixed lubricants, extreme-pressure lubricants, and encapsulated lubricants. The advantages and disadvantages of these lubricants are compared and the outlooks for the development of water based drilling lubricants are expected.

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    • Laboratory Screening and Evaluation of Surfactant Flooding System with Salt Resistance

      ZHOU Ming

      Abstract:

      Aiming at the problems of unsatisfactory injection production ratio in the actual oil production and development process of Yanhua 182 Well Group, low production and low energy of development wells, high salinity, high calcium and magnesium ions in formation water resulting in the failure of conventional surfactant, a system of surfactant flooding with anti-salt was prepared. Without chelating agent and stabilizer, the system of surfactant flooding consisted of PPM-12(bis{[(N-methylN-(3- dodecanoxy-2-hydroxyl) propyl-N-(2-hydroxyl-3-sulfonic acid sodium) propyl] methylene} ammonium chlorides),AES-12 (sodium lauryl ether sulfate) and OB-2 (dodecyl dimethylamine oxide). The optimum total concentration of surfactant flooding system was 0.3wt%, and the suitable weight ratio range was 4:1:1-1:1:4. The optimum ratio is 2:1:3, and the oil-water interfacial tension can reach the lowest value (0.0012 mN.m-1). The adsorption, emulsification, salt resistance of the composite surfactant flooding system was studied under optimum conditions. The results of adsorption performance showed that the system was still in the order of 10-3 mN.m-1 after six adsorption. The results of emulsification showed that the water separation time of the system was 3995s. The experimental results of resistance to sodium, calcium and magnisesium ions showed that the system could reach the order of 10-3 mN. m-1 in the range of sodium, calcium and magnesium ions in the oilfield. Magnesium ions have the greatest influence on the interfacial tension of the system, followed by calcium ions and sodium ions. Experiments show that the PPM-12, AES-12 and OB-2 compound system is suitable for EOR of Chang 6 reservoir of Hua 182 well groups, with an average EOR of 10.3%. It has a good application prospect in similar high salt and low permeability reservoirs.

      • 1
    • Synthesis and performance study of the high temperature-resistant acid gelling agents

      LI hui, LUO bin

      Abstract:

      Compared with other acid gelling agents, amphoteric gelling agents have the advantages of low price and convenient synthesis and can improve the viscosity of acid based on supramolecular effect of gelling agents. Hence, amphoteric gelling agents have wild application prospect in acidizing fracturing field. Two amphoteric gelling agents were synthesized from acrylamide (AM), 2-acrylamide-2-methylpropanesulfonic acid (AMPS), dimethyl diallyl ammonium chloride (DMDAAC) and methacryloyloxyethyl trimethyl ammonium chloride (DMC) by free radical aqueous solution polymerization. The results indicated that acid dissolving time of two amphoteric gelling agents less than 40 min. The viscous acid containing the compound of two amphoteric gelling agents mixed in a certain mass ratio was 39 mPa·s at room temperature (25°C) and 170S-1and was 15 mPa·s at 160°C and 170S-1 after continuous shear for 90min, which demonstrated that the compound had excellent viscosity increasing property, temperature resistance and shear resistance performance

      • 1
    • The effects of wettability on water coning in bottom water reservoirs

      HU junjie, ZHANG guicai

      Abstract:

      The wettability of the rock has an important influence on the delay of the water coning recovery after the bottom water reservoir is pressed, but the degree of its influence is not clear. In view of this, four wetting adjustment systems with different wetting abilities were constructed with the contact angle as the index of wetting agent, which were dissolved in oil-soluble viscosity reducer, and their properties were evaluated. On this basis, the intrinsic relationship between wettability and production property conditions was quantitatively described, and the degree of influence of wettability on inhibiting water coning recovery was further illustrated. The results show that the reservoir under the action of oil wetting agent has the best effect of inhibiting bottom water recovery, the equilibrium pressure ratio reaches 3.75, and the net recovery degree increases by 15.17%. However, the equilibrium pressure ratio of the reservoir under the action of strong water wetting agent is only 0.54, and the net recovery is increased by 6.51%. There is an obvious regularity between wettability and produced physical properties. Adjusting the wettability of the reservoir can effectively restrain the rise of the water cone and improve the oil recovery.

      • 1
    • Development and application of micro-expansion degradable gel temporary plugging agent for acid fracturing

      WU Wenchuan, YU Xiaorong

      Abstract:

      Diversion acid fracturing is one of the effective measures to increase production of carbonate reservoir. Importantly, the key of this technology lies in the temporary plugging agent. However, the existing acid fracturing with temporary plugging agents are of poor acid resistance, complicated removal process, and high cost. Aiming at solving those problems, a micro-expansion temporary plugging agent (WDS) for acid fracturing was prepared through aqueous radical polymerization in this study. The degradation performance, temporary plugging performance, and reservoir damage of the WDS were studied, and it was applied in field construction. The results showed that it was first micro-expanded and then degraded in different solutions. The complete degradation time of the WDS reduced from 78 h to 45 h with the rising temperature from 70 ℃ to 120 ℃. The complete degradation time reduced from 75 h to 48 h with the rising concentration of HCl from 3% to 20%. According to the results of displacement experiment, with the increase of the injection, the temporary plugging pressure increased, and the time to reach the maximum temporary plugging pressure reduced. And with the increase of the fracture width, the temporary plugging pressure decreased, and the time to reach the maximum temporary plugging pressure increased. In addition, the WDS was less harmful to the core, and the permeability recovery value of cores of more than 90%. Furthermore, the field application results indicated that the construction pressure increased by 10 MPa after adding the WDS, and the effect of temporary plugging was remarkable. In conclusion, the WDS can be completely degraded under the conditions of temperature, acid, and salinity, and the effect of temporary plugging is remarkable. It has a good application prospect in diverting acid fracturing.

      • 1
    • Synthesis, Characterization and Drag Reduction Properties of a Long-chain End-group Hydrophobically Associative Polymer

      YANG LIN

      Abstract:

      In order to develop a new type of slick water drag reducer, this paper uses terpolymer of acrylamide (AM), hydrophobic monomer dodecyl dimethylallyl ammonium chloride (C12DMAAC), and sodium acrylate (NaAA) as raw materials. The long-chain end-group hydrophobic associative polymer HPAM-L was synthesized by the self-made long-chain hydrophobic initiator AIBL. The performance was characterized, and the friction resistance of HPAM-L solution at different concentrations was measured by a flow loop friction tester. The results show that the viscosity-average molecular weight of HPAM-L is about 7.43 × 106 g/mol, the critical association concentration is about 1~1.5 g/L, and it has good temperature resistance and shear stability. The aqueous solution of HPAM-L has a wide range of Linear viscoelastic region, and the higher the concentration, the more obvious the elastic characteristics. When the solution concentration is 0.075%, 0.086%, 0.1% and 0.15%, the maximum drag reduction rate can reach 71.6%, 73.1%, 73.3% and 74.1%, respectively, and the drag reduction performance is good.

      • 1
    • Analysis of Factors Affecting Silicon Removal by Hydroelectric Flocculation Depth in Ultra-heavy Oil Production

      YANG Changgen, FAN Yuxin

      Abstract:

      Electrocoagulation has been treated by experiment on deep silicon removal of super-heavy oil produced water using aluminum plates as cathode and anode. The optimal PAC dosage, pH value ,current density and PAM dosage are obtained through single factor variables. The results show that single electrocoagulation can not achieve deep silicon removal. Electrocoagulation together with PAC and PAM has a synergistic effect on the removal of silicon from super-heavy oil produced water. The effluent of SiO2 by electrocoagulation reaches 20mg/L and the SiO2 removal rate is 92% when the PAC is 200mg/L, the pH is 8.0, the current density is 10mA/cm2, and electroflocculation time is 13 minutes, which can achieve deep silicon removal. With the increase of electric flocculation time, the removal rate of SiO2 increases, but the rate of change decreases.

      • 1
    • Synthesis and demulsification performance evaluation of nano iron sol stabilized by biosurfactant

      ZOU Jing, WANG Zhengliang

      Abstract:

      In view of the high cost and pollution of physical and chemical demulsifiers in the demulsification process of oilfield wastewater, it is necessary to study and synthesize new environmentally friendly demulsifiers. In this paper, a combination of sol-gel and solvothermal method is used to prepare biosurfactant (Biosurfactant, BS) stabilized nano-iron sol materials, to study the optimal BS concentration, and use SEM, XRD, FTIR, laser particle size analyzer, Zeta Potential etc. characterize the BS-stabilized nano-iron sol, and study its morphology, size, phase, functional group, sol stability, particle size distribution and other influencing factors. The demulsification performance of the synthesized nano-iron sol on the oily sewage emulsion prepared by the oil-water mixture on Weizhou Island was investigated. The results showed that after fermentation of the glycolipid biosurfactant T bacteria with a specific medium for 6 days, the supernatant after centrifugation was taken to synthesize iron sol. When the concentration of supernatant was 80 % and 100 %, iron particles with diameters of about 200 nm and 40 – 200 nm could be synthesized, respectively. When the concentration was 60 %, the demulsification effect of nano-iron sol product was the best. At low temperature, it could produce good demulsification effect on the oil-in-water emulsion formed by sodium dodecyl sulfate, and the dehydration rate reached 78 % after 24 h. It shows that the method used in this paper can synthesize BS stable nano-iron sol with good demulsification characteristics. It is suggested that biological metabolites and chemical agents should be combined organically in the future to prepare environmentally friendly composite nano-demulsifiers, while studying its repeated use and other issues.

      • 1
    • Measurement of relative permeability curve of heavy oil - water by nuclear magnetic resonance

      Pu Wanfen, Chang Jiajing

      Abstract:

      Relative permeability was an important basic measurement parameter in heavy oil development experiment. Due to the high viscosity of heavy oil, oil-water emulsification was prone to occur during water flooding process, which made it difficult to obtain the heavy oil-water relative permeability curve accurately. The traditional measurement method of relative permeability curve regarded the core as a "black box", and measured the volume of oil and water at the outlet by the method of manual reading or weighing, which had the disadvantages of low measurement accuracy and less information. In order to accurately measure the heavy oil-water relative permeability curve, this paper selected the long artificial sandstone core. Based on the nuclear magnetic resonance measurement technology, through the simultaneous calibration of crude oil and formation water of Bohai B reservoir, the unsteady state method was used to measure the heavy oil-water relative permeability curve, and the T2 spectrum test was carried out on the core and the produced fluid at the outlet. Thus, the pore volume (147.18cm3), irreducible water saturation (25.9%), residual oil saturation (43.83%) of the core and the oil and water content at the outlet were obtained more accurately, and the heavy oil-water relative permeability curve was obtained more accurately. Moreover, the D/T2 two-dimensional spectrum test was carried out on the produced fluid with oil-water emulsification, and the emulsification of oil and water was judged more accurately. The research results can provide some theoretical guidance for the development of heavy oil water flooding, which is beneficial to the study of the mechanism of heavy oil water flooding.

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    • Preparation and Performance Evaluation of Depressurization and Oil-displacing Agent in Low Permeability Reservoir

      QU Huimin

      Abstract:

      Affected by reservoir physical properties, there is a contradiction between the insufficient formation energy and difficult water injection in water flooding development of low permeability reservoirs. On the one hand, the water injection pressure is high and the underinjection is serious. On the other hand, the formation pressure drop of low permeability reservoirs is large, the productivity decreases rapidly, and the oil recovery rate and recovery degree are low. After water flooding, there are still many forms of residual oil such as membrane or oil droplets. In view of the above problems, this work synthesized metronidazole asymmetric Gemini surfactant, and combined with dehydro rosin surfactant, cetyl alcohol, ethanol to form a functional enhanced injection and oil displacement agent. The agent reduces the interfacial tension between oil and water, emulsifying crude oil and removing oil film. The cationic component forms molecular film on the rock surface with water as the transfer medium, stabilizes clay, improves the wettability of rock surface and reduces water injection resistance. Combined with the field test of pressure flooding, the daily oil increment of the well group is 13.4 t/d at the beginning and 12.6 t/d after 5 months. The injection capacity of the well was significantly improved. Before pressure flooding, the injection volume of the water well is 0 at the high pressure of 30 MPa, and 30 m3/d at 27.5 MPa after pressure flooding.

      • 1
    • Plugging Mechanism and Prevention of Oil Well in Polymer Flooding Reservoir

      LIU Ying, WANG Zengbao

      Abstract:

      Polymer flooding widely used in oilfields for a long time corresponds to serious plugging of oil wells and decreased liquid volume, which seriously affects the further development of reservoirs after polymer flooding. Using XRD, SEM and other technical means to analyze the composition and composition of oil well plugging products; through different plugging fluid simulation and near-well reservoir condition simulation, the plugging degree and main controlling factors of oil well plugging are studied. The results show that the plugs in the oil wells of polymer flooding reservoirs are mainly polymer aggregates that are cross-linked and embedded to adsorb formation mineral salts and clays, accounting for 65.6%; followed by formation sand particles and cements, and crude oil, respectively, 17.8 %, 16.6%. The plugging of porous media caused by the formation of sand particles is the main controlling factor of plugging near the oil well. The polymer agglomerates formed by polymer derivative cross-linking and adsorption agglomeration aggravate the degree of blockage of the oil well. Based on the guidance of the research on the plugging mechanism of polymer flooding reservoirs, the near-well crude oil cleaning of plugged oil wells + the oxidative degradation of polymer micelles, the integrated prevention and control program of oil well plugging and sand control for the effective sand consolidation control of far wells has good application effects, and the average single well extraction 86.8%.

      • 1
    • The Effect and Mechanism of Surfactants with Different Interfacial Properties to Improve Oil Recovery

      LIU Qian

      Abstract:

      Taking the low permeability tight reservoir of Chang 6 as the research object, two self-made surfactants S1 (with strong modification wettability) and S2 (ultra-low interfacial tension) with different interfacial properties were selected. Their static and dynamic permeability effects were characterized by NMR, and their oil displacement process was studied by 2.5-dimensional micro model, The EOR effect and mechanism of surfactants with different interfacial properties are analyzed. The results show that both S1 and S2 have good enhanced production effects. Imbibition is a process in which water enters small pores to replace oil to large pores. Surfactants can greatly promote the production of small pores; During oil flooding, the dominant channel is obviously formed, which can realize wettability reversal, and has additional imbibition effect, which greatly increases the sweep volume and oil washing efficiency, and can disperse the crude oil into small scale state. Among them, the S1 capillary with stronger wettability ability is more powerful and has a higher degree of mobilization of small holes, but the recovery rate is slower, but the additional imbibition during displacement is stronger, which can achieve ultra-low interfacial tension.The S2 with ultra-low interfacial tension can achieve smaller oil phase flow resistance, faster imbibition speed, and faster recovery to reach equilibrium.

      • 1
    • Accelerating the dissolution of hydrophobically associative polymers by Cyclodextrin

      李玺

      Abstract:

      Hydrophobically associating polymers are highly concerned for their excellent rheological performance. However, the poor dissolution caused by the interactions of hydrophobes restricts their popularization and application on oilfields. Irreversible viscosity loss of polymer solution will inevitably occur through the current physical accelerated dissolution modes. In this paper, cyclodextrins (CDs) are used to accelerate the dissolution of the hydrophobically associating polymer by the inclusion of hydrophobic groups, and avoiding solution viscosity loss. The inclusion of cyclodextrins on hydrophobes improves the interaction of associating polymers with solvents, and as the molar ratio of cyclodextrin to hydrophobic groups (CD: [H]) increases, the dissolution time of the hydrophobically associating polymer decreases exponentially. Rheology results have shown that CDs can significantly shorten the dissolution time of the hydrophobically associating polymers by disrupting association structures of hydrophobic groups through inclusion. Utilizing the competitive inclusion properties of cyclodextrin inclusion complex, the rheological properties of the solution can be completely restored by adding an appropriate amount of nonionic surfactants with stronger affinity to the CDs to the hydrophobes of associating polymer.

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    • Performance evaluation and application of the microbial huff and puff system for Sheng li oil field Luo 9 Shi 1 block

      CAO Gongze, LI Caifeng

      Abstract:

      Luo 9 Shi 1 block has some problems of high temperature, high viscosity, high water cut and low water flooding efficiency.In order to improve the output of high water cut oil well, the composite system of biological polysaccharide and microorganism was developed. Its temperature resistance, plugging performance, emulsion viscosity role and model of the displacement effect were studied. Finally, the composite system of huff and puff was applied in the field.The results showed that the viscosity of the new biological polysaccharide remained in the range of 120 ~ 125mPa.s at 55 ~ 95℃ and the temperature resistance was strong.When the new biological polysaccharide injected into the core, the pressure increases by 5.6 times and the permeability decreases by 53.3%, which could effectively seal the core.When the ratio of microbial fermentation liquidⅠto microbial fermentation liquidⅡwas 1:2, the high temperature emulsification ability was the strongest and the emulsification viscosity reduction rate was 81.4%. The physical simulation of oil displacement experiment showed that the composite system of biological polysaccharide and microorganism improved oil recovery by 13.9%, which was better than the single system in oil displacement. The application results of five oil Wells showed that four oil Wells had achieved success and the cumulative increase of oil amounted to 2730t. The effect of increasing oil and dewatering was significant, which continued to be effective.It effectively improved the low efficiency of oil well in Luo9 Test 1 block.

      • 1
    • Development and Evaluation of cryogenic Microbial Demulsification System in shale oil production fracturing fluid

      Gong Zhaobo, Ma Ting

      Abstract:

      In order to meet the demand for demulsification in Xinjiang oilfields, and reduce the environmental pollution of common oilfield chemicals, this article based on environmental safety and the complex situation of shale oil fracturing produced fluids in the Madong block in Xinjiang, and fifteen kinds of biodemulsifiers synthesized by microbial fermentation were screened and evaluated by the bottle test method. The demulsification of the fermentation broth and the purified extract was compared, and the results showed that the biodemulsifier XJ-4-2 synthesized by the XJ-4 bacteria had good compatibility with the extracted fluid from the Madong block and more than 80% dehydration rate. In order to improve the demulsification efficiency and reduce the cost, a composite system of biological demulsifier and conventional chemical demulsifier is adopted. After optimization, the demulsification efficiency of the composite system of biological demulsifier XJ-4-2 and chemical polyether demulsifier reaches above 95%. Through the optimization of the dosing process, the initial water content is 43.76%. When the chemical demulsifier 200mg/L is added at 60 ℃, the dehydration rate after 2h sedimentation is 91.45%, the remaining water content ratio of crude oil was 8.43%, and the oil content ratio of sewage is 228mg/ L. The initial water content of the improved crude oil is 33.85%. At 50 ℃, when the compound formula 200mg/L is added, the dehydration rate after 2h sedimentation is 94.56%, the remaining water content ratio of crude oil 1.84%, and the oil content ratio of sewage is 156mg/L. In summary, the biological demulsifier has high dehydration rate at low temperature and low sewage oil content. It is of great significance for the efficient separation of produced fluids from fracturing exploitation of shale oil in the Madong block and ensuring the normal operation and economic benefits of the oilfield.

      • 1
    • Static Adsorption of JCP-1 Nano-spheres on Mineral Surface in Liquid Phase

      JIANG Xu, CHEN Junbin

      Abstract:

      Nanospheres have been widely used in low permeability reservoir development. In order to study the adsorption mechanism of nano-spheres on rock and mineral surfaces, it is necessary to quantitatively characterize the influence of mineral types on the adsorption capacity of nano-spheres on rock and mineral surfaces. Firstly, starch - cadmium iodide method was used to calibrate the concentration of JCP-1 nano-microsphere emulsion, and then the adsorption capacity of the microspheres on the surface of single component mineral and multi-component mineral was determined respectively. Then, based on the measured data of microsphere adsorption on the surface of single component minerals, the predicted value of microsphere adsorption on the surface of multi-component minerals was obtained by weighted superposition according to the relative content of rock minerals. The results show that the static adsorption capacity of JCP-1 nanospheres on different mineral surfaces varies greatly. The adsorption capacity of clay minerals to microspheres is generally stronger than that of non-clay minerals. Kaolinite has the strongest adsorption capacity for this type of microspheres, which is 14.75 times stronger than quartz. The adsorption capacity of the microspheres on the surface of potash feldspar is much stronger than that of the other two non-clay minerals, and the variation value of adsorption capacity is 1.96 times and 8.42 times of that on the surface of albite and quartz, respectively. For the adsorption capacity of microspheres on the surface of multi-component minerals, the relative error between the predicted value of weighted superposition method and the measured value is within 3%. Finally, based on the adsorption phenomenon at solid-liquid interface during the migration of nanospheres in pore channels, it is considered that the clay minerals on the pore walls strengthen the adsorption of microspheres, which is beneficial to change the pore radius and achieve "partial fluid flow direction" under the condition of "incomplete plugging".

      • 1
    • Cationic Surfactant Pretreats Formation to Enhance Squeeze Life of Scale Inhibitor

      SONG Haojun, REN Shaoran

      Abstract:

      In the process of seawater injection development in offshore oilfields, the incompatibility of injected water and formation water often leads to serious sulfate scaling in oil wells. Although the squeeze treatment can be used to prevent scale, the squeeze life of the scale inhibitor is generally shorter. This article considers adding an adsorption enhancer to the pre-flush to increase the adsorption capacity of the scale inhibitor in the formation and reduce the desorption speed of the scale inhibitor. Quaternary ammonium surfactant DTAC and cationic gemini surfactant GS-A6 were selected as adsorption enhancers, and sodium polyacrylate PAAS was selected as scale inhibitor. The compatibility experiment, static adsorption experiment and dynamic adsorption-desorption experiment of adsorption promoter and scale inhibitor were carried out. The results show that at 120℃, the two adsorption enhancers have good compatibility with the scale inhibitor, and the adsorption enhancer can effectively increase the adsorption amount of the scale inhibitor in the formation and prolong the squeeze life of the scale inhibitor. The adsorption enhancer DTAC was greatly affected by oil saturation, and the adsorption enhancement effect decreased significantly at high oil saturation. The adsorption enhancer GS-A6 has a stable adsorption enhancement effect under different concentrations and different oil saturation conditions, and is suitable for oil well scale inhibition in different development stages.

      • 1
    • Integrated Thickener with High-Viscosity and High-Drag Reduction used for Fracturing Deeper Shale Gas

      WEI Juanming

      Abstract:

      Slick water hydrofracking represents an important technique for the efficient development of shale gas, but there are a series of challenges such as low viscosity, large freshwater consumption and slick water-to-gel transition, which limit its application in hydrofracking of deeper (>3500 m) shale gas reservoirs. To address these issues, an integrated thickener with high-viscosity and drag reduction (HVFR) was synthesized by free radical polymerization, and their solubility, thickening ability, drag reduction and proppant carrying capability as well as heat- and shear-resistance were examined. The results showed that the viscosity-average molecular weight of HVFR is 22.7 x 10^6 g/mol, and the HVFR exhibited a rapid dissolution rate with thickening rate of 93% within 1 min, which is conducive to the online continuous mixing of fracturing fluid. At a flow rate of 150 L/min, the drag reduction can reach higher than 70% for both low- and high-viscosity slick water, and up to 68% for gel. It is also demonstrated that HVFR thickener exhibited multifunctional properties and can be freely transited between low- and high-viscosity slick water as well as gel by altering the concentration of HVFR. The cross-linked fracturing fluid based on HVFR displayed not only remarkable heat- and shear-resistance, but also proppant carrying capacity. The viscosity of the cross-linked fracturing fluid can be maintained at 120 mPa*s after shearing for 120 min at 120 oC and 170 s^(-1).

      • 1
    • Performance evaluation of low density elastic sealing cement slurry to improve the sealing capacity between cement layers

      XING Xuesong

      Abstract:

      Abstract: Under the existing cementing slurry technology, ensuring the long-term stability of wellbore integrity is facing challenges, especially the conventional low-density slurry. After perforation, the integrity of cement stone is damaged more seriously, resulting in sealing failure, poor cementing quality between cement stone and casing and well wall, and channeling is easy to occur. In view of the above problems, it is preferred to use compound liquid fiber to improve the strength and toughness of cement paste, nano lightening agent to improve the settlement stability of cement slurry, and 10% res-1 elastic material is preferred to reduce the elastic modulus of cement paste and improve the deformation capacity of cement paste. The comprehensive performance evaluation of low-density elastic sealing cement slurry was carried out in the laboratory. The results show that the 1.5g/cm3 low-density elastic sealing cement slurry system has good rheology, adjustable thickening time of cement slurry, water loss less than 50ml, and linear expansion rate of 0.45%, which can effectively inhibit the generation of micro annulus and micro gap. Compared with ordinary low-density cement slurry, the permeability and elastic modulus of low-density elastic sealing cement slurry are reduced by 69.5% and 78.4% respectively, and the compressive strength and flexural strength are increased by 61% and 54% respectively, indicating that the cement slurry has good compactness, flexibility and elastic deformation ability. The evaluation of the sealing capacity of the cement sheath shows that under the conditions of alternating pressure range of 20mpa-40mpa and pressure rise and fall frequency of 5 times, the anti channeling strength in the simulated sealing is greater than 7 MPa/m2, which can effectively improve the long-term sealing capacity of the cement sheath and improve the cementing quality.

      • 1
    • Research on the Mineralized Deposition of Nanoparticles and Its Application Exploration on the Improvement of Wellbore Stability

      Liu Zhendong

      Abstract:

      In the drilling of shale formation, the problem of wellbore stability is relatively prominent. Due to the special physical and chemical properties of shale, it is easy to absorb water and expand, resulting in the wellbore falling and collapsing, so it is necessary to reinforce the wellbore during drilling. In this paper,the process of biomineralization is simulated to study the self-assembly technology of nanoparticles. Based on the selection of cationic polymers and nanoparticles, this paper focused on the self-assembly deposition process of modified calcium carbonate and BPEI, as well as the structural analysis of the deposition layer. The experimental results displayed that modified nano-calcium carbonate could form a well deposition layer on the simulated well wall. In addition, this paper also explored the application of this technique on the improvement of wellbore stability which would provide a new strategy to solve the problem of wellbore instability.

      • 1
    • Dynamic analysis and preparation of drag reduction and sand-carrying dual-functional polymer materials for shale fracturing

      ZHOU Cheng-yu

      Abstract:

      In order to solve the problems of large frictional resistance at the front end and low viscosity at the tail end of volumetric fracturing in shale reservoirs. The steric hindrance of twin tail monomers with different carbon chain lengths, mean square terminal distance and mean square displacement (MSD) of the polymer materials were studied based on molecular dynamics. The drag reducer LMA-AM-DiC12AM (LAD) was synthesized by micellar polymerization with Lauryl methlacrylate (LMA), Acrylamide (AM) and N,N-dodecyl acrylmaide (DiC12AM). The rheological properties, drag reduction and sand carrying properties of LAD solution were studied by rheometer and friction tester. The results show that DiC12AM monomer has small steric hindrance, the best chain flexibility of polymer materials molecules, the best ability to bind water molecules, and the great drag reduction potential. LAD has good shear stability (viscosity is 75mPa·s) and shear recovery performance. It can withstand a temperature of 60℃ at present. Its drag reduction rate reach 67.4%. The average sedimentation rate of 40/70 mesh ceramsite is 2.05×10-4 mm/s. The polymer materials agent has both drag reduction and sand carrying properties, which is basically consistent with the simulation results.

      • 1
    • Application of the Nanoparticles Augmented Enhanced Oil Recovery

      ZHANG Xiaojun, GUO Jixiang

      Abstract:

      Nanoparticles(NPs) are seen as potential solutions to overcome the challenges, such as low sweep efficiency, associated with these traditional EOR techniques. The application of nanoparticles augmented chemical EOR, gas EOR, and thermal EOR techniques in recent years have been summarized in this paper. The main principles, characteristics and research results of the nanoparticles augmented EOR process were introduced. Also, EOR challenges using NPs and the needed future research are highlighted. It provided foundation for the development of NPs augmented EOR technologies.

      • 1
    • Development and performance evaluation of high temperature-resistant core-shell nano plugging agent used for oil-based drilling fluid

      Du Zhenghong, Peng Wu

      Abstract:

      Nano pores and micro fractures are well developed in shale formation. However, the particle size of conventional plugging agent is large and it is difficult to plug pores and fractures in shale. A high temperature-resistant core-shell nano plugging agent CLG-NM was prepared with inorganic nano silica as the core and poly (styrene-butyl acrylate-acrylic acid) as the shell. The plugging agent was characterized by infrared spectroscopy, transmission electron microscopy, dynamic light scattering and thermogravimetry, and its plugging performance was evaluated by shale pressure transfer experiment. The results show that the particle size distribution of CLG-NM is 40 ~ 300 nm, the median particle size is 89.4 nm. CLG-NM maintains thermal stability below 372 ℃. Furthermore, CLG-NM has good compatibility with oil-based drilling fluid. After 3% CLG-NM was added into the oil-based drilling fluid of Weiye 28-7hf well, the rheological property of the drilling fluid changed slightly. The high temperature and high pressure filtration (aging at 180oC for 16h) decreased from 3.1mL to 2.8mL, and the demulsification voltage kept higher than 700mV. Compared with KC-2 and PT-seal, CLG-NM has better plugging effect on the nano pores and fractures in shale.

      • 1
    • Research on Polyelectrolyte Hydrophobic Associated Composite Suspension Stabilizer for Cementing

      ZHAO Qiyang, CHEN Xuewen

      Abstract:

      In deep and ultra-deep oil and gas resource cementing, due to the high temperature of the formation, some admixtures in the cement slurry fail at high temperatures, resulting in serious settlement of solid particles and loss of stability of the slurry, which increases the risk of channeling during cementing. In this work, a polyelectrolyte hydrophobic association composite suspension stabilizer P-AB with good temperature resistance was studied. The results of infrared spectroscopy, thermogravimetric analysis, particle size analysis and cryo-scanning electron microscopy show that: P-AB can form a unique grid structure through electrostatic interaction and hydrophobic association, which helps prevent cement slurry settlement and free water separation ; 1% P-AB aqueous solution can maintain a high viscosity at 40℃-150℃; after adding 0.5%-1% of P-AB to the cement slurry at a high temperature of 200℃, the density difference between the upper and lower sections of the cement stone will be less than 0.02 g/ cm3, the free liquid of the slurry is 0, and Zeta potential analysis shows that the addition of P-AB can improve the dispersion performance of the slurry. This technology is conducive to improving the cementing quality of deep and ultra-deep wells and reducing cementing risks.

      • 1
    • Research Progress of Active Components in Crude Oil and Interaction on Influence of Emulsion Stability

      SUN Lin, Ren Zihan

      Abstract:

      A large amount of emulsion is easily formed in the process of crude oil production due to the existence of active components, including asphaltene, resin, petroleum acid, and wax. Based on the composition and existing state of active components in crude oil, the influence mechanism of each active component on the emulsion stability was described. The interaction between active components and asphaltene with their influence on emulsion stability is summarized. Among the active components of crude oil, these are pointed out asphaltene is the main component of the interfacial film, and suitable resin with asphaltene can strengthen emulsifying effect. The results between carboxylic organic acid and asphaltene are various owing to different relative molecular weights, and the wax can enhance the strength of the interfacial film when they crystallize or interact with asphaltene. Meanwhile, current problems and future development directions are prospected.

      • 1
    • Preparation and properties of gel dispersion for profile-controlling and flooding by aqueous RAFT polymerization

      YANG Ziteng, ZHANG Peng

      Abstract:

      Based on reversible addition fragmentation chain transfer (RAFT) aqueous polymerization, the micro/nano-polyacrylamide gel dispersions for profile-controlling and flooding were prepared to solve the problems of complicated preparation processes of common profile-controlling and flooding agents and the need to add organic solvents. A new water-soluble RAFT agent was synthesized, and then polyacrylamide gel dispersions were prepared by using the RAFT agent in water. The effects of reactant ratio, polymerization temperature, polymerization time and solid content on its properties were investigated. The rheological and viscoelastic properties of gel dispersions were tested. The temperature response, salinity responsiveness and pH responsiveness of gel dispersions were characterized. The results showed that the viscosity of gel dispersions decreased with the increase of temperature and decreased with the increase of pH value, but had little effect, and their viscosity was almost not affected by mineralization. Finally, the microstructure and particle size were characterized by atomic force microscope (AFM), scanning electron microscope (SEM) and nano particle analyzer. The results showed that the gel dispersion was irregular globular structure. The micron diameter of the gel dispersions was 0.92 ~ 6.13 μm and the diameter of the nanoparticles was 48 ~ 76 nm, which confirmed that the molecular scale of gel dispersions prepared by RAFT aqueous polymerization was micro/nano scale.

      • 1
    • Preparation and performance evaluation of polymer microsphere as drilling fluid filtrate additive

      Liu Yun

      Abstract:

      As the existing filtrate reducers often have an unsatisfied performance in the high temperature and high salinity environment, a polymer microsphere is synthesized by inverse emulsion polymerization of water-soluble monomers (sodium p-styrene sulfonate, 2-acrylamide-2-methylpropanesulfonic acid and acrylamide) using liquid paraffin as the continuous phase, Span 80 and Tween 60 as emulsifier. Infrared spectroscopy, thermogravimetric analysis, scanning electron microscope and laser particle size analyzer are used to characterize the product. Then the swelling performance, salt resistance, aging performance, temperature resistance and plugging experiments also are studied. It is shown that microspheres display a spherical morphology with a particle size of 2.82-10.26 μm, and begin to decompose at 270 ℃. It is found that the final expansion ratio in deionized water approaches to 500%. In addition, microspheres exhibit a good fluid loss reduction performance in high salinity and high temperature conditions, and have anti-aging property. After plugging experiments, the polymer microspheres are observed in macropore of core slice, where plug performance is achieved by polymer microspheres.

      • 1
    • Preparation and analysis of acrylate- methacrylic acid copolymer emulsion reversed demulsifier

      ZHANG Tao

      Abstract:

      Requirements for sewage treatment chemicals are very high due to the limited sewage treatment equipment and short residence time in offshore oilfield. Thus, it is necessary to develop a high-efficient reversed demulsifier to improve the separation efficient of oil and water. In this work, acrylate-methacrylic acid copolymer emulsion reversed demulsifier (EMASA) was synthesized via emulsion polymerization method by using EA, MAA and SA as precursors. The structure and thermal properties of synthsized copolymer were characterized using FT-IR?, 1HNMR and DSC. The oil removal rates of synthesized copolymers were further investigated based on the water from the offshore oilfield A platform(water type is sodium bicarbonate). Results suggests that the oil removal rate of EMASA was 96.5% under a filling concentration of 30 mg/L, and the value further increased to 98.9% at the assistance of the flocculant,ECHA. Pilot scale test of the property of EMASA was further carried out on platform A. It was found that the OIW at the outlet of the oil system decreased from 255.75mg/L to 197.58mg/L under a EMASA filling concentration of 30mg/L, and the oil removal rate of the oil system increased from 94.89% to 96.05%. The mechanism of the role of EMASA was also clarified based on the results of dynamic light scattering, interfacial tension and expansion modulus.

      • 1
    • Experimental investigation of zeolitic imidazolate framework nanoparticles for enhanced oil recovery

      HE Xuan, LIU Yuetian

      Abstract:

      Nanomaterials have attracted extensive attention in the study of enhanced oil recovery due to their unique physical and chemical properties. However, there are still some shortcomings such as poor dispersion, easy agglomeration and low recovery rate. It is very important to synthesize new nanoparticles and apply them to the research of enhanced oil recovery. In this paper, ZIF-8 nanoparticles were prepared for EOR applications and their microstructures were characterized by X-ray diffraction and field emission scanning electron microscopy. In order to prepare the nanofluids, the nanoparticles were dispersed in brines with different concentrations, which were characterized through analyzing their stability. Then the prepared nanofluids were used to measure the interfacial tension and contact angle between crude oil and water on the surface of sandstones. Finally, the core displacement experiments were carried out. The results show that the average diameter of the prepared ZIF-8 nanoparticles is 65.8nm, and the phase state is single without impurities. When the mass fraction is not higher than 0.03%, the dispersion in water is excellent, and the absolute value of Zeta potential is about 30mV, which has a high stability. After adding 0.03% ZIF-8 nanoparticles in simulated formation water and low salinity water, the interfacial tension values decreased to 4.662 and 3.965mN/m, respectively, which decreased by 75.76% and 73.27% compared with that without adding. The contact angle decreases from 114°, 109° to 78° and 73°, respectively, and the rock surface towards to more water-wet, which is more conducive to the peeling of oil film. Thus, the recovery was increased by 8.25% and 10.71% with 0.03% ZIF-8 nanofluid under the high and low salinity conditions, respectively.

      • 1
    • Anti-blocking system in water injection process of low permeability loose sandstone reservoir with high clay

      Liang Yukai, Yu Xiaocong

      Abstract:

      Aiming at the problem of high injection pressure caused by particle migration blocking the reservoir pore throat in the process of water injection in high clay loose and low permeability sandstone reservoir, a neutral gradient anti plugging system was optimized through laboratory experiments. The low-speed gradient anti plugging system is 0.5% KCl clay stabilizer, and the high-speed gradient anti plugging system is 0.2% KCl + 0.3% organic cationic clay stabilizer. The anti-swelling property of gradient anti plugging system and the changes of core pressure and permeability during displacement were investigated. The results showed that the anti-swelling rate of the system was more than 91%. Compared with the blank production water displacement, at low speed, after being treated by the anti-plugging system, the pressure growth multiple was reduced from 5.41 to 2.03, and the permeability retention rate was increased from 18.49% to 49.15%; At high speed, after being treated by the anti-plugging system, the core permeability gradually recovered. When 8PV was replaced by production water, the permeability retention rate increased from 10.56% to 91.58%, and the pressure growth multiple decreased from 9.47 to 3.28. The plugging prevention system is neutral, which provides a strong support for the advanced green water injection and efficient development of low permeability reservoirs.

      • 1
    • Evaluation and application of polymer microsphere / surfactant composite profile control and flooding system

      WU Tianjiang

      Abstract:

      According to the characteristics of Changqing Low Permeability Reservoir, polymer microsphere / surfactant composite profile control and oil recovery technology is proposed. The initial particle size of polymer microspheres is generally 50-300nm, and it has hydration expansion characteristics with expansion ratio of 5-10 times. The aggregation characteristics of microspheres during hydration and expansion were observed by SEM, and the particle size distribution was Gaussian normal distribution. The most economical concentration of surfactant is 0.3%. The results show that the viscosity of the mixture increases after adding surfactant to polymer microspheres, and the dispersed phase particles of microspheres shield the interfacial activity and micelle formation ability of surfactant, which results in the decrease of interfacial tension, which is not conducive to surfactant flooding. When the mass concentration of microspheres is greater than 0.4%, the plugging rate is more than 80%. The best injection mode of polymer microspheres and surfactant is slug injection with volume ratio of 1:1. The application effect of this technology in Ansai Oilfield is good, and the cumulative oil increase is 3576t, showing good technical adaptability.

      • 1
    • Synthesis and Properties of a MultipStudy on Synthesis and properties of reinforced materials for oil well cement

      Liu Xuepeng

      Abstract:

      In this paper, a heterogeneous particle was synthesized from diphenylmethane diisocyanate (MDI), polyepoxypropane glycol, silicate aqueous solution and heavy calcium carbonate, which was used to reduce the elastic modulus of oil well cement. The first phase of multiphase particles is a porous continuous phase, and the second phase is basically spherical; In the multiphase particles, the second phase is embedded in the holes of the first phase, and the spherical second phase contains 18 ~ 20% Si element. The experimental results show that the cement stone with multiphase particles has lower elastic modulus than that of neat paste cement stone, but the strength does not decrease; Multiphase particles have little effect on the thickening time and rheology of cement slurry; The spherical structure at the interface of multiphase particles contains a large number of silicon hydroxyl groups, which participate or partially participate in the hydration of cement, forming a permeable structure at the interface to ensure the continuity of cement hydration structure.

      • 1
    • Foam Properties and CO2/N2 Response Properties of Anionic Surfactant/ Tertiary Amine Compound Foam

      LIU Dong-Mei, SUN Shuang-Qing

      Abstract:

      In this paper, the foam performance of sodium dodecyl sulfate (SLS), sodium dodecyl sulfonate (SDS), sodium dodecylbenzene sulfonate (SDBS) and N-dodecyl-N, N-dimethyl tertiary amine (C12A) equimolar compound solution were studied through foam experiments, and the influence of inorganic salt and oil relative to the foam performance of the compound system. In addition, for the SLS/C12A compound system and SDS/C12A compound system with better foam performance, CO2 response defoaming and N2 heating recovery re-foaming and defoaming experiments were carried out. The research results show that the SLS/C12A compound system has the best foam stability and strong salt tolerance. The anti-oil effect of the SDS/C12A compound system is remarkable, and the two compound systems both show good CO2 responsiveness and reversibility. According to the change of the solution and the change of surface tension after defoaming, the response mechanism is inferred that the protonated C12A and anionic surfactants are electrostatically attracted to form a complex, which precipitates out of the solution, which reduces the surface activity of the solution and accelerates the breaking of the foam.

      • 1
    • Research progress and application prospects of drilling fluid additives in intelligent water-based drilling fluid chemical system

      Shen Haokun

      Abstract:

      Traditional water-based drilling fluid has some disadvantages, such as tedious process of drilling fluid configuration, poor pertinence and weak adaptive ability. Intelligent water-based drilling fluid has become a new research direction in the field of oilfield chemistry because of its better pertinence and universality, and can greatly reduce the degree of manual intervention. Through literature analysis, the mechanism and research progress of intelligent materials such as intelligent water-based drilling fluid additive in water-based drilling fluid are described. According to the characteristics of different intelligent drilling fluid additives, the feasibility of intelligent materials in water-based drilling fluid is discussed, and the research ideas, methods and application prospects of intelligent drilling fluid additives in intelligent drilling fluid system are prospected.

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    • The Research and Oilfield Trial of Horizontal Well Selective Water Shutoff Agent in Glutenite Oil Reservoir

      Li Yikun

      Abstract:

      The Kunbei glutenite reservoir has thick layer and strong heterogeneity in plane, interlayer and intralayer. In the early stage of development, the horizontal well production yield decreases and water cut rises rapidly. Horizontal wells are in urgent need of water control. Based on the characteristics of Kunbei reservoir and production, Acrylamide (AM)-2-acrylamido-2-methylpropanesulfonic acid (AMPS)-dimethyldiallylammonium chloride (DMDAAC) terpolymer selective water shutoff agent for horizontal wells was synthesized. The injection performance of water shutoff agent was investigated by rheological mechanics experiment, and the selectivity of water shutoff agent was investigated by core plugging simulation experiment. The core experiment shows that the injection pressure is increased by 6.06 times after water plugging, the water flooding plugging rate is 83.5%, and the oil displacement plugging rate is 20%, which has remarkable oil-water selectivity.On the basis of laboratory experiment and well performance, the oilfield trials of water shutoff for 6 horizontal wells have been carried out in Kunbei Oilfield. The remarkable effect of increasing oil and reducing water has been gained.

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    • Application of New Low-damage and High-performance Micro-foam Drilling Fluid in Coalbed Methane Wells in Eastern Yunnan

      Ma Tengfei, Zhou Yu

      Abstract:

      The third member of Feixianguan Formation and the first member of Feixianguan Formation in eastern Yunnan are easily unstable formations. In order to protect coal bed reservoirs, new low-damage high-performance micro-foam drilling fluid technology is designed and applied. The developed foaming agent LHPF-1 was compounded with foaming agent BS-12 and tackifier XC, and the response surface optimization experiment was used to analyze the influence of the interaction between the three treatment agents on the foam composite index Fq. On this basis, fluid loss agents and inhibitors are optimized, and the final microfoam drilling fluid formula is determined to be: 0.25%LHPF-1+0.25%BS -12+0.25%XC+1%SPNH+1%NH4HPAN+0.2%KPAM. The research results show that the density of the drilling fluid can be reduced to 0.49g/cm3, the foaming volume can reach 420mL, the half-life of the foam can reach more than 2000min, the thickness of the foam liquid film can reach 50% of the foam size, and the coal core plugging rate and permeability The recovery value is above 90%, and it is resistant to 7% of debris and coal pollution. The drilling fluid was applied on-site in the second opening section of Well LC-C7-2D in the Laochang exploration area in eastern Yunnan. The pure drilling time was 4 days without any complicated downhole accidents. The average caliper expansion rate for the whole section was 5.9% , The fluid loss is less than 5mL.

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    • Study on the low-damage slick water fracturing fluid of Baikouquan Formation in Mahu 1# well area

      ZHANG Ying, YU Weichu

      Abstract:

      Baikouquan formation in Mahu 1# well area is a typical tight oil reservoir with low porosity and low permeability, which large-scale hydraulic fracturing is need to increase production. However, there are three major problems. First, the fracturing fluid has poor drag reduction effect and is harmful to the reservoir. Second, water resources are scarce and oil field sewage treatment is difficult. Third, the recovery rate needs to be improved because of the distribution of residual oil between the joints. So, the JHFR drag reduction agent was synthesized which is low-damage. And then, JH slick water fracturing fluid with low damage was constructed. JH mainly composed of 0.1% JHFR drag reduction agent and 0.2% JHFR multifunctional additives. The fluid is characterized by instant dissolution (15 s), high efficiency drag reduction (76.9%), low oil-water interfacial tension (0.89 mN/m), and good anti-swelling effect (CST ratio 0.92)., and other characteristic. The system has good compatibility with formation water and backflow fluid in the Mahu 1# well area, and the damage degree to core permeability is low. So, it is suitable for large-scale continuous fracturing in the Mahu 1# well area.

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    • Study and Field Application of Organic Boron/Zirconium Composite Linear Gel Fracturing FluidWAN Qingshan1*, BAI Lei1,LI Bin2,CHEN Liyan1,ZHAKE Jian1

      Wan Qingshan

      Abstract:

      Based on the formation principle of partially hydrolyzed polyacrylamide (HPAM) and polyhydroxyl alcohol weak gel, the crosslinking agent FHBZ-1 was used to prepare the crosslinking gel with HPAM and polyhydroxyl alcohol, and it was used as the fracturing fluid of LG-2 composite linear gel. Zirconium crosslinking agent was prepared by mass ratio of Zirconium chloride, lactic acid, propyl alcohol, triethanolamine of 6:5:1:24 in 75℃ water bath for 2h. Boron cross-linking agent was prepared by mass ratio of Borax, mannitol, water/glycerol (volume ratio 3:1) Mixed solvent, NaOH of 18:16:6:2, pH value: about 10, reaction temperature: 80℃, reaction time 5h.The organic boron crosslinking agent and the organic zirconium crosslinking agent were mixed according to the volume ratio of 1:2 to form FHBZ-1.The crosslinking, temperature resistance and shear resistance of LG-2 linear gel fracturing fluid system were evaluated respectively.Experiment from LG - 2 linear gel fracturing fluid optimization ratio of 0.3% (wt) HPAM + 0.5% (wt) CPA - 1 + 1.2 (v) % FHBZ - 1 + 0.05% (v) ZP + 0.3% + 0.05% APS NW (v).The final viscosity of 448mPa?s was obtained by shear at a constant speed of 170s-1 for 90min at 130℃, indicating its good temperature and shear resistance.The performance of LG-2 linear glue fracturing fluid was evaluated at 60 and 90℃. The viscosity of LG-2 linear glue fracturing fluid was small, and the amount of residue was low, which was about 16mg/L and 12mg/L, respectively.Field test of WY-8 shale gas well verified that LG-2 linear glue fracturing fluid system has excellent performance of seam making and sand carrying.

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    • Research on Mechanism of Pickering Microemulsion Control Swelling of Clay in Heavy Oil Reservoir

      Guo MIngzhe

      Abstract:

      Inhibition of clay expansion is a premise of effective thermal recovery in water sensitive heavy oil reservoir, however, a quantitative description of mechanism that stabilizer inhibits clay expansion, which is remaining unclear. First, a Pickering microemulsion applied to control clay swelling was proposed, besides mechanism of expansion inhibition Pickering microemulsion was analyzed by combination of Fick"s law and Langmuir theory of adsorption. Then, effect of Pickering microemulsion formed by the compounded mixtures of hydrophobic nano SiO2 and lauryl three methyl ammonium bromide (DTAB) on water surface tension was tested, and the suppression bentonite’s swelling rate of the Pickering microemulsion was also measured, which obtained optimum formulation. Finally, the dynamic anti-swelling effect of the Pickering microemulsion was studied by slug displacement experiments through best formula. The quantitative analysis shows that it is feasible to prevent clay swelling by surface adsorption. When the ratio of nano-SiO2 to DTAB is 1:2 and the concentration is 0.6wt%, the best inhibition effect of bentonite was obtained. The best slug injection volume is 0.2PV in test. with unceasingly increasing microemulsion injection volume, the anti-swelling effect was more obvious. But the rate of increase of water cut also was accelerated, which indicated that the clay swelling should be properly controlled in heavy oil reservoirs with high permeability.

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    • water-soluble resin-based cementing fluid system

      HE Yingzhuang, YAN Siming

      Abstract:

      In view of the problems of gas channeling and wellhead pressure caused by high pressure and fracturing in the development of oil and gas fields, water-soluble resin was used as the main cementitious materials and a resin-based cementing fluid system at low and medium temperature was prepared. The engineering performance, anti-channeling ability, mechanical property, temperature resistance and curing kinetics of the system were studied. The results show that the density of the resin system can be adjusted to 1.20~1.80g/cm3 through the combination of weighting agent and suspending agent, and it has good flowing ability. The thickening time can be adjusted from 60 to 410 min by changing the dosage of curing agent and accelerator between 60℃ and 90℃. When the displacement efficiency is 91.5%, the consolidation strength of cured resin is 3.01 MPa, the interface breakthrough pressure is more than 12 MPa, which is much higher than that of conventional cement stone under similar displacement efficiency. The compressive strength of cured resin is above 50MPa after curing at 90℃ for 24h, and the elastic recovery rate is more than 85% after six cycles of alternating stress loading, which is better than that of ordinary set cement. The TG analysis demonstrates that initial decomposition temperature of cured resin is 398℃, which indicates that the resin-based cementing fluid has good temperature resistance. The curing kinetics equations of S-HR/CA-1and S-HR/DCY systems, and the relationship between curing degree and curing time was determined. The resin cementing fluid has consolidation strength and strong deformation recovery ability at the cementing interface, which is conducive to ensuring the long-term integrity and sealing performance of cementing material, and preventing fluid channeling of oil and gas wells. The study of curing kinetics provides a theoretical reference for the research and application of this kind of resin working fluid system.

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    • Demulsification Mechanism of quartz sand on heavy oil emulsion

      ZHANG Dianchen, ZHANG Shijian

      Abstract:

      Because the heavy oil emulsion is opaque and it is impossible to intuitively understand the influence of sand particles on the stability of heavy oil emulsions, some scholars have detected the asphaltenes adsorbed on the surface of mineral particles by Fourier transform infrared spectroscopy. It is speculated that these particles destroy the strength of oil/water interfacial film due to the adsorption of asphaltenes on the oil/water interfacial film and promote the aggregation of water droplets,Sso as to realize demulsification and stratification of heavy oil emulsion.SHowever, this understanding cannot explain some phenomena in our experiment. In this paper, experiments such as bottle experiment, rheology test and wettability test are carried out, and the influence mechanism of quartz sand on the stability of heavy oil emulsion is obtained: when the sand particle size is small and the water droplet particle size is large, the phenomenon of water droplets completely wetting and wrapping the sand particles will occur, the proportion of water droplets wrapping the sand particles will increase, and the settlement speed will accelerate,SThis is the main reason for the demulsification and stratification of heavy oil emulsion by sand, and this understanding is also verified by the sedimentation experiment of sand in white oil.

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    • Synthesis and evaluation of a new small molecular clay stabilizer ZWS-1with high temperature resistant

      SHEN Huibing, WU Pingping

      Abstract:

      In view of the problems such as poor washing resistance of inorganic salt clay stabilizer, easy adsorption and blockage of pore channel and poor temperature resistance of polymer clay stabilizer, it is urgent to develop a new type of small molecule clay stabilizer for high temperature and low permeability reservoir. In this work, high temperature resistant clay stabilizer ZWS-1 was synthesized with trimethylamine and γ-chloropropyltriethoxysilane. The optimized weight concentration of ZWS-1 applied for clay stabilization was 1.5%. A synergistic effect was observed on 5% ZWS-1 and 4% KCl, which exhibited a decrement of clay swelling of 98.3%, and the washing resistance of 91.4% at 150 ℃. The characterization results indicate that ZWS-1 leads to the agglomeration of clay particles and increase the stability of clay. Fourier transform infrared spectroscopy (FTIR) results reveal that ZWS-1 reacts with hydroxyl groups of the clay surface, which indicates that the presence of chemical bond between ZWS-1 and clay minerals.

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    • Research on Imbibition of Surfactant to Improve the Production Characteristics of Crude Oil in Matrix-fracture Dual Media

      WANG Xingkun, DAI Caili

      Abstract:

      Surfactant imbibition is an important means to improve the production of tight oil matrix crude oil and the characteristics of surfactant imbibition in the tight oil matrix-fracture model to improve crude oil production was studied in this paper. First, 0.05 wt% of ASB is preferred as a surfactant for imbibition by spontaneous imbibition, measuring interfacial tension, and wettability. Furthermore, through the matrix-fracture core model and the microfluidic model, the effects of the fracture tortuosity and the velocity in the fracture on the dynamic imbibition of the near-fracture matrix to improve the production characteristics of crude oil were studied respectively. The results show that the degree of crude oil recovery by dynamic imbibition of the near-fracture matrix increases with the increase in the tortuosity of the model, that is, the higher the fracture complexity, the higher the degree of dynamic imbibition recovery; the faster the flow velocity in the fracture, the oil-water interface in the capillary the faster the migration rate, that is, the faster the imbibition rate, and the migration rate of the oil-water interface and the flow velocity in the fracture conform to the law of quadratic function as a whole. Also besides, the effects of the action depth and concentration of surfactant on the spontaneous imbibition of the deep matrix to improve the production characteristics of crude oil were studied through static imbibition experiments. The results show that the deeper the surfactant action depth, the lower production of crude oil per unit volume. When the surfactant concentration is high, the variation law of the degree of spontaneous imbibition production is consistent with the interfacial tension as the main control parameter of the capillary force is the interfacial tension. When the surfactant concentration is low, the main controlling parameter of the capillary force is the wettability of the rock surface. At this time, the variation law of the degree of spontaneous imbibition and production is opposite to the interfacial tension.

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    • Efficient preparation of nano starch particles and its effect on the performance of drilling fluid

      Ma Peng, Zhang Lei

      Abstract:

      In order to meet the requirements of environmental protection and efficient drilling of unconventional shale reservoirs, it is necessary to develop a new type of drilling fluid system with excellent performance and environmental friendliness. In this paper, ultrasonic treatment and precipitation method are combined to solve the problem. First, ultrasonic treatment is used to reduce the viscosity of starch solution with a high concentration of 5%. Thus, the precipitation method is used to prepare nano-starch particles under the condition of high concentration starch solution. After preparation by the method, the average size of the nano starch particles is as small as 30nm, and the particle size is mainly concentrated in 20-50nm with a relatively uniform distribution. The salt resistance of the nano starch particles is 20g/L NaCl at 150°C. After adding 1.0% nano starch particles to the base slurry, the apparent viscosity, plastic viscosity, dynamic shear force and fluid loss are 22.0 mPa.s, 14.5 mPa.s, 11.5 Pa and 9.3 mL, respectively. After aged at 150℃, the apparent viscosity, plastic viscosity, dynamic shear force and fluid loss after 16 hours are 21.1 mPa.s, 14.0 mPa.s, 10.8 Pa and 10.0 mL, respectively. More importantly, nano-starch particles and bentonite can form a network structure, which can increase the apparent viscosity, plastic viscosity, and shearing force of the drilling fluid, and decrease fluid loss, and it can still maintain excellent performance after aging under high temperature. The combination of ultrasonic treatment and sedimentation method is easy to be operated, low cost, easy to be promoted and applied. The formed technology can provide an important technical support for the development of a new type of nano-drilling fluid system.

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    • Dynamic characteristic and mechanism of different types surfactant for detaching residual oil film

      XU Guorui, LI Xiaoxiao, ZHOU Jingjing, WANG Shuo, LI Xiang, LIU Fenggang

      Abstract:

      Oil film is an important type of residual oil after water flooding, and improving its utilization will further enhance oil recovery(EOR). To investigate the dynamic detachment characteristics of different types of surfactants on oil films, a visual physical simulation method for oil film detachment was used to quantitatively characterize the dynamic characteristic parameters. Through 11 different types of typical surfactants, the effects of different molecular structure and properties of surfactants on the mobilization rules and function mechanisms of oil films were clarified. The results show that there are significant differences in the dynamic characteristics and detachment mechanisms of different types of surfactants for peeling oil films. The detachment of oil films by anionic surfactants is mainly affected by the number of hydrophilic groups in the molecular structure and the emulsifying performance, while the detachment effect of cationic surfactants on oil films is mainly affected by the number of hydrophilic groups in the molecular structure, interfacial tension(IFT) and the wettability alteration. Non-ionic surfactants are mainly affected by the synergistic effect of the number of hydrophilic groups in the molecular structure, interfacial tension, and emulsifying performance. This results can further guide the molecular structure design of surfactants and the theoretical investigation of oil displacement.

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    • Growth law of indigenous microorganisms producing dispersions in low permeability reservoirs and its application potential for regulating flooding and plugging

      Gao Yiwen, WEI Dengfeng, Wang Weibo, NI Jun, GUAN Yaqian, GUO Maolei, WANG Qianrong, CUI Kai

      Abstract:

      The Yanchang oilfield in the Ordos Basin, characterized by its tight to ultra-low permeability reservoirs, faces challenges in fluid flow during development processes such as water and CO2 injection due to its inherently low matrix permeability, strong heterogeneity, and the widespread occurrence of naturally developed micro-scale fractures. In the practical application of traditional profile control and water plugging techniques in oilfield operations, the range of profile control is limited to the near-wellbore zone. Although it can enhance the water absorption profile of injection wells, the phenomenon of water channeling in the deep formation has not been fundamentally improved. Currently, chemical reservoir deep-profile control agents often exhibit application deficiencies, leading to issues of either being difficult to inject or incapable of effective plugging. This passage utilizes reservoir microbial resources to develop a green, low-carbon microbial dispersant for profile control agents. The dispersant consists of indigenous microbial cells and their metabolic products, forming small spheres (microbial dispersal bodies) that grow as individual entities and are dispersed in the aqueous phase. This innovative microbial dispersant is employed to address the application bottleneck of conventional chemical profile control agents. Research results indicate that the optimal activation and growth conditions for dispersant-producing bacteria (Novosphingobium sp., with a similarity of 98-99%) in low-permeability reservoirs are as follows: temperature of 40-45°C, salinity of 60000 mg/L, and pH of 7-8. The viscosity of the microbial dispersant solution is 2 mPa.s, primarily exhibiting a viscous effect. Additionally, it demonstrates excellent salt resistance (up to 100000 mg/L) . The profile control and plugging mechanism of the microbial dispersant involve the adaptive growth characteristics of individual functional bacteria within the dispersant, matching the porous medium environment. The dispersant continuously migrates to the depths of fractures and high-permeability porous media, altering the flow direction of injected water/CO2 gas, ultimately achieving full-profile control. Rock core displacement experiments indicate that the microbial dispersant exhibits excellent profile control and plugging capabilities in water and CO2 displacement environments, with plugging rates exceeding 90%. Microbial dispersant profile control and plugging technology show promising applications in low-permeability reservoirs.

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    • Dissolution and distribution of CO2 in coexisting formation oil and water

      YANG Renfeng, ZHANG Lijun, TAN Xianhong, TIAN Xiaofeng, YANG Xugang, SHU Xiaohan, ZOU Guodong, YANG Erlong, JANG Changdong, HU Shaobin

      Abstract:

      In order to reveal the dissolution law of CO2 in formation oil-water mixture, with the oil and water from BZ25-1 reservoir, the dissolved amount of CO2 in coexisting oil and water under different water saturation, pressure and temperature conditions was tested through high-pressure physical property experiments. The results show that with other conditions unchanged, with the increase of pressure, the dissolved amount of CO2 in oil and water increases, but the amount of dissolution in oil increases more, and the proportion of dissolved CO2 in the water decreases, As the pressure increased from 18MPa to 31MPa, the percentage of CO2 dissolved in water to that dissolved in oil decreased from 22.96% to about 12.51%; With the increase of temperature, the dissolution of CO2 in oil increases, while the dissolution in water does not change obviously, and the proportion of dissolved CO2 in water decreases slightly, as the temperature increased from 125℃ to 145℃, the percentage of CO2 dissolved in water to that dissolved in oil decreased from 13.41% to 10.35%; the water saturation basically has no effect on the dissolved amount of CO2 in oil and water, but with the increase of water saturation, the ratio of the dissolved CO2 in water to that in oil increases, as the water saturation increases from 35% to 65%, the percentage of CO2 dissolved in water to that dissolved in oil increases from 13.43% to 48.81%, under the condition of water saturation of 65%, in order to reach the saturated CO2 state of oil, about 50% extra CO2 needs to be injected due to the dissolution of CO2. Therefore, in order to fully dissolve CO2 into crude oil to improve its physical properties and thus to improve the production effect by CO2 injection, it is beneficial to increase the injection pressure as much as possible, to keep the formation at a high temperature, and to increase appropriately the injection amount of CO2 according to the water saturation to meet the consumption of CO2 dissolution in water.

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    • Research and Application of Fine Layered Chemical Sand Control in Complicated Fault-Block Reservoir

      LI Jianda, QIAN Qin, CAO Gongze, LI Peng, WANG Guoqiang, HAN Hong

      Abstract:

      To solve the problem of the uneven injection of sand consolidating agents in strong heterogeneous reservoir, a fine layered chemical sand control technology based on the "intralayer low viscosity active agent sand consolidation and interlayer selective seperate layer sand control" was carried out. Indoor tests showed that the low viscosity active sand consolidation system was characterized by the good injectability, low damage and high consolidation strength. The viscosity of the sand consolidation system was 4.5mPa·s, the permeability of the consolidated sand core was more than 1 μm2, and the compressive strength of the cemented core was more than 5 MPa. The selective seperate layer chemical sand control string was complemented based on the injection parameter optimization, which could implement the selective injection of sand consolidation agents. The fine layered chemical sand control performed well in field tests. After a cumulative production of 2700 days, the liquid production of the test well was 52.4 m3/d, and the oil production was 5.3 t/d. The production and effective period have been significantly improved. It is of great significance to prolong the lifespan and increase the efficiency of sand control wells in complex fault-block reservoir.

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    • Construction and performance of MoS2 nanoflooding system with high dispersion stability

      GAO Yanbo, FAN Hui, WANG Fang, ZHOU Juan, WANG Xiaoye, DONG Xianpeng, LU Licheng

      Abstract:

      For domestic low permeability reservoir accounted for more and more large, conventional flooding agent cannot meet the requirements of production, nano flooding material because of its good injection, small reservoir damage, improve the oil recovery effect is obvious and is applied to low permeability reservoir mining, the MoS2 nanoscale because of its simple preparation method and low cost by more and more attention. However, due to the poor dispersion stability of nanomaterials in low permeability reservoirs, they often need to play a synergistic role with surfactant to improve their performance. It is of very important significance to clarify the interaction between MoS2 and surfactant to improve the application range of MoS2. Here, MoS2 nanosheets were synthesized by hydrothermal method, using thioacetamide as sulfur source and molybdenum trioxide as molybdenum source. The effects of different surfactants on the dispersion stability of MoS2 nanosheets in saline was studied, and a new nanoscale oil-driven system CTAB-MoS2, and finally, the interfacial performance and enhanced recovery performance of CTAB-MoS2 was constructed. The experimental results showed that the introduction of CTAB significantly improved the dispersion stability of MoS2 nanosheets in 3000 mg/L NaCl solution, the self-stabilization time of 0.1wt.% CTAB-MoS2 increased from less than 3h to 12h, the average particle size of CTAB-MoS2 decreased from 122.7nm to 98.1nm compared with MoS2, and the absolute value of Zeta potential changed from 25 mV to 33.8mV. CTAB-MoS2 can spontaneously form interface membrane and climbing membrane at the n-heptane/water interface, and can reduce the tension of n-heptane / water interface to 0.175 mN/m, and also has good emulsifying effect. Based on its excellent salt tolerance and good interface activity, CTAB-MoS2 has some enhanced oil recovery effect in the hypotonic environment. Only 0.5PV concentration of 0.005wt.% was injected at 60℃ and NaCl concentration of 3000 mg/L. The construction of CTAB-MoS2 is expected to provide a solution for the efficient development of low permeability fields and a research idea for improving the dispersion stability of nanomaterials.

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    • Development and performance evaluation of anti-multivalent cationic fluid loss agent

      Cao Jiajun, Zhang Yongwei, Qin Yuqing, Yu Jiashui, Yu Ting, Yang Lili

      Abstract:

      Complex geological circumstances arise during the discovery and exploitation of oil and gas. Drilling into layers of salt and gypsum results in formation water with a very high mineralization content. This water may also contain a significant amount of divalent and trivalent metal cations, such as Al3+, as well as Mg2+ and Ca2+, which can seriously affect the viscosity and fluid loss reduction of water-based drilling fluids. In order to create an anti-multivalent cation zwitterionic hyperbranched polymer fluid loss reducer, or XZ-DJ2, this article presents a branching agent based on zwitterionic polymers to address this issue. Experiments were conducted to investigate the ideal reaction conditions and characterize several physicochemical characteristics. The base slurry containing 2% XZ-DJ2 had filtration losses of 5.6 mL and 6 mL, respectively, before and after aging at 150 °C for 16 hours, according to performance testing. The filtration losses were 6.3 mL, 6.2 mL, 5.2 mL, 6.8 mL, and 7.0 mL, respectively, following 16 hours of age at 150 °C with 30%NaCl,30%KCl,5%CaCl2,5%MgCl2 and 1%Al2(SO4)3.18H2O . This indicates that XZ-DJ2 has excellent temperature resistance and resistance to multivalent cation contamination and XZ-DJ2 achieves the goal of reducing filtration loss by improving the density of filter cake rather than increasing the viscosity of drilling fluid, which is conducive to drilling speed increase and further saves drilling fluid operation costs.

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    • Evaluation of the Indoor Mobilization Performance of Nanoscale Particle Dispersions

      QIAN Zhihong, YU Xiaoling, WANG Lei, ZHU Jie, DAI Zhipeng, ZHANG Guicai

      Abstract:

      Dissection plugging is an important means to improve the recovery rate of water drive in high water content oilfield, and granular plugging agent is widely used as an important chemical plugging agent. In this paper, the flow of self-developed nano-sized oil-soluble resin particles dispersions of conditioning repellents in cores and their blocking ability were tested using a core replacement device. The injection performance and plugging performance of oil-soluble resin dispersions conditioning repellents within the formation were mainly evaluated using the replacement pressure as an index. The experimental results show that the oil-soluble resin dispersions conditioning repellents have good injection performance and blocking performance. As the concentration of the oil-soluble resin increases, the injection pressure of the oil-soluble resin dispersion rises. As the formation permeability decreases, the injection pressure of the oil-soluble resin dispersion increases. And when the resin concentration is 5%, the dispersion system has good injection performance in formations with different permeability. The blocking rate of oil-soluble resin dispersion on the ground layer increases with the increase of oil-soluble resin concentration, and the blocking rate remains basically unchanged when the resin concentration exceeds 5%. The blocking rate increases as the formation permeability decreases and provides a good blocking effect at formation permeabilities of 30 mD or less. In addition, the oil-soluble resin dispersions have good scour resistance in formations of all permeabilities. Keywords: nanoparticle dispersions; alternation experiment; profile control and water plugging; enhanced oil recovery

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    • Research Progress of superhydrophobic materials for oil-water separation

      ZHENG Lintao, WANG Ruifang, ZHOU Ming, ZHANG Tianci

      Abstract:

      The processes of oil extraction, transport, and paper production lead to the generation of large quantities of oily wastewater, which poses a great threat to the living environment of human beings. Traditional oil-water separation strategies are usually inefficient, costly and cumbersome. Therefore, it is crucial to develop new, green, economical and efficient materials for oil-water separation. Superhydrophobic materials have attracted much attention in the field of oil-water separation due to their unique properties. In this review, based on the research on superhydrophobic materials used for oil-water separation in recent years by scholars at home and abroad, we firstly give a brief introduction to superhydrophobic materials, and then focus on the research progress of two-dimensional and three-dimensional superhydrophobic oil-water separation materials. Finally, an outlook is given for superhydrophobic oil-water separation materials, including considerations for sustainability and environmental friendliness. This thesis aims to provide some references and inspirations for the research of superhydrophobic materials in the field of oil-water separation.

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    • Molecular design and miscible interaction of miscible flooding agent based on molecular simulation

      JIA Junhong, FAN Wei, LI Mei, DAI Shanshan, QIN Sen, YANG Jialong, WANG Ruiyao

      Abstract:

      In this work, molecular simulation was introduced into the design of molecular structure and the study of mixing mechanism of miscible flooding agents, which partly solved the problems of long time and high cost of slim tube experiments. First, the structures of five types of functional groups with mixed-phase potential were initially identified, and the affinity of each type of functional group for CO2 was judged based on quantum mechanics by using the electron transfer in the process of electron density and Fukui function studies as well as the energy change in the process of adsorption reaction energy and frontier orbital studies. The molecular structure design of the amphiphilic miscible flooding agents was carried out based on the full consideration of the number of functional groups and spatial site resistance. Based on molecular dynamics, the interactions and dispersion aggregation of the three miscible flooding agents, simulated oils and CO2 were investigated, and the mixed-phase ability of the Miscible Flooding Agents was comprehensively evaluated in combination with the diffusion coefficient. The results showed that increasing the number of pro-CO2 groups synergized with the appropriate spatial site resistance was beneficial to enhance the down-mixing effect.

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    • The biological toxicity source of sulfide agents and some correspondent treatment methods

      WANG Chunsheng, ZHU Jinzhi, ZHANG Zhen, ZHANG Shaojun, WU Xiaohua, LUO Xiao, LI Qiang

      Abstract:

      Sulfonated treatments commonly used in deep-well water-based drilling fluids have significant biotoxicity without exact sources, leading to the restriction of environmental protection regulations when used. To solve this problem, the relationship between the physicochemical characteristics (such as functional groups, molecular weight and molecular structure, content of heavy metals and organic poisons, particle morphology) of typical sulfonated treatments and their biotoxicity was analyzed. Results showed that the sulfonic acid groups in agents were not biotoxic, the molecular weight and structure were unrelated to the toxicity, and the traces of heavy metals and organic toxicants were negligible factors. The removal of residue by dialysis through a semi-permeable membrane and the followed separation of water using a Soxhlet extractor makes the treatments biologically non-toxic, further demonstrating the predominate contribution of residual sulfonating agents (sodium bisulfite and sodium metabisulfite) and the adsorptive inactivation of solid-phase large particles dispersed in water on the Vibrio fischeri to the biotoxicity. Finally, depolymerized the sulfonated agent using a homemade MOF and applied in drilling fluid, satisfactorily, the rheological properties, API and HTHP filtration loss in that biologically non-toxicity system were both almost perfectly consistent with the original agents, providing powerful technological support for the application of sulfonated treatments.

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    • Quantitative analysis of OP-20 and SDS binary complex system

      YANG Guojun, JIANG Yi, SHI Dongpo, WANG Yuan, SUN Jianxiao, ZHU Shenghua, TIAN Minglei, LI Geng

      Abstract:

      A method for the determination of the content of each component in the binary surfactant system of octylphenol polyoxyethylene ether (OP-20) and sodium dodecyl sulfate (SDS) was studied and established. The content of OP-20 in OP-20/SDS binary complex system was detected by ultraviolet spectroscopy. SDS had a significant effect on the absorbance and critical micelle concentration (ccmc) of OP-20. After adding 0.3 mmol/L SDS, the absorbance of OP-20 at the maximum absorption wavelength of 224 nm increased from 1.727 to 1.751, and the ccmc decreased from 0.223 mmol/L to 0.198 mmol/L. HP-β-cyclodextrin (HP-β-CD) has a significant masking effect on the detection of OP-20 in the OP-20/SDS binary complex system by ultraviolet spectroscopy. Job's experiments showed that HP-β-CD and OP-20 were included in a molar ratio of 1:1. After adding HP-β-CD, the content of OP-20 in the complex system can be accurately detected by ultraviolet spectroscopy. The recovery rate changed from 96.42% ~ 106.92% to 99.28% ~ 101.38%, the interference of SDS on OP-20 was significantly reduced. The experimental results of FT-IR and 1H-NMR showed that the reason for eliminating the mutual interference between SDS and OP-20 was that the OP-20 molecule entered the HP-β-CD molecular cavity and formed an inclusion complex. The content of SDS in OP-20/SDS binary complex system can be accurately detected by conductivity method, and OP-20 will not significantly interfere with the detection of SDS by conductivity method. When the concentration of OP-20 in the solution is 0.1 ~ 0.3 mmol/L, the recovery rate of SDS in OP-20/SDS complex system is 100.83 % ~ 101.92 %. This method can effectively detect the content of each component in the OP-20/SDS binary surfactant system.

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    • Evaluation and Application of In-situ Emulsification Flooding System in 95℃ High Temperature Reservoir

      Liu Yu, Liu Yanhua

      Abstract:

      According to the characteristics of high temperature reservoir in Henan oilfield, in-situ emulsification flooding system was developed at 95℃ and its performance was evaluated. The results showed that the selected surfactant had good solubilization ability of crude oil, which can form micro emulsion system with crude oil in situ, has ultra-low interfacial tension, good adsorption resistance and temperature resistance, and the oil washing efficiency was 78%. Considering the strong fluidity of the micro emulsion, the optimized temperature resistant polymer has high mobility control capability that under the water quality conditions of 0.2mg/L~0.4mg/L oxygen content and 15mg/L~20mg/L sulfur content, the viscosity retention rate that more than 100% can be achieved after aging at 95℃ for 60 days. The experiment of natural core flooding showed that the phase characteristics of the produced liquid and core slice pores in in-situ emulsification flooding were obvious, the heavy components of crude oil were effectively displaced, and all types of remaining oil were well used, which had the ability to form emulsification flooding in the whole process of displacement. Further variable concentration step injection combined with profile control slug injection can increase the recovery rate by 28.4% in heterogeneous core test. At present, the technology has entered the stage of pre-slug injection in the mine field, and the digital-analog predicted enhanced recovery rate of 8.06 percentage points.

      • 1
    • Effects of High-temperature Resistant Resin Powder on the Performance of Cement Slurry in Thermal Recovery Wells

      LIU Weihong, WANG Xiaoliang, HU Qianhong, XU Mingbiao

      Abstract:

      During the exploitation process of heavy oil reservoirs, the thermal stress generated by the injection of high-temperature steam often leads to the failure of cement. Aiming at this problem, a type of poly aryl ether ketone high-temperature resistant resin powder was selected as elastic material to be added to the cement slurry, and the influence of resin powder on the conventional properties, mechanical properties, and high-temperature resistance of the cement was studied. The results showed that when 4% resin powder was added to the cement slurry, the consistency coefficient of the cement slurry was 0.80Pa·sn, the filtration loss was 34mL, the thickening time was 225 minutes, and the compressive strength was 17.69MPa. The conventional performance of the cement slurry met the requirements of on-site operations. The elastic modulus of cement stone can be reduced to below 4GPa, indicating that the addition of resin powder can improve the elasticity of cement stone. After 28 days of high-temperature curing at 320 ℃, the compressive strength of cement stone was 18.68 MPa, the impact strength was 1.97 KJ/m2, and the elastic modulus was 3.67GPa,which exhibited good high-temperature resistant strength and elasticity. Compared with the cement stone without resin powder, the permeability of the cement stone decreased by 61.3%, the elastic modulus decreased by 39.1%, and the peak strain increased by 119.0%. The addition of resin powder reduced the brittleness of cement stone, increased its elasticity and capability of anti-deformation, and can effectively enhance the ability of cement stone to resist thermal stress damage during steam injection operations in thermal recovery wells.

      • 1
    • Synthesis and Performance Evaluation of Double Cross-linked Gel Plugging Agent Used in High-temperature and High-Salinity reservoirsYANG Zu-guo1,3, MA Qin-jie2,3, GUO Ji-xiang1, GUO Jin-tang4

      YANG Zuguo, GUO Jixiang, MA Qingjie, GUO Jintang, GAO Qiuying

      Abstract:

      The high temperature and high salinity reservoirs put forward higher requirements for gel materials, compared with conventional reservoirs. The existing gel has the problems of short gel time, poor dilution resistance and poor long-term stability under high temperature formation conditions. We designed a two-stage cross-linked gel structure, the temperature-resistant and salt-resistant double-crosslinked gel plugging agent was synthesized by solution polymerization using glycidyl methacrylate ( GMA ) and diethylene glycol dimethacrylate ( EDMA ) as main raw materials, polyethylene glycol ( PEG ) as solvent, tert-butanol hydrogen peroxide ( TBHP ) as initiator system and fumed silica ( AEROSIL ) as reinforcing agent. We studied the effects of monomer dosage, crosslinking agent dosage, initiator dosage and reinforcing agent dosage on the gelation time and elastic modulus of the gel. The results show that the initial viscosity of the system is 350mPa . s, the gel time is 2 ~ 10h, the elastic modulus is 5230Pa, and the compressive strength is 0.221MPa.In the simulated formation water with a salinity of 2.2 × 105 mg / L, there is no volume shrinkage after aging at 140 °C for 30 days. The elastic modulus can reach more than 4000Pa, and the reverse breakthrough pressure gradient of the displacement experiment reaches 5.5MPa / m.

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    • Performance and application of self-settling high strength casing plugging agent

      XU Guorui, GUO Yonghua, WANG Xiaolong, CHANG Zhen, LI Xiang, FENG Xuan

      Abstract:

      Wellbore integrity management is one of the key issues to ensure the safe production of oil and gas Wells. At present, there is still a lack of self-developed plugging agent materials with the same plugging ability as foreign products. In view of this, through the optimization of the main agent and curing agent system, a liquid high-strength plugging agent was developed in this paper. The material has low initial viscosity (90 mPa·s) and high plugging compressive strength, and has good settling and curing performance. The mechanism of solidification and good plugging ability of the plugging agent was analyzed by scanning electron microscopy and infrared spectroscopy. The plugging simulation test was carried out, which confirmed that the plugging agent has excellent pressure capacity (>160 MPa/m), and can settle and cure at a height of 20 m, which has a strong plugging ability. Finally, the system was applied in A horizontal well in south east china sea, and the leak point plugging operation was successfully completed. This study provides a new pure liquid sealing system for wellbore integrity management, and the product has good application potential.

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    • Preparation and Performance Study of Rubber Powder-Doped Flexible Particle Plugging Agent

      YANG Zuguo, XI Linhui, GUO Jixiang, XUE Yan, LI Liang, LI Shenglin

      Abstract:

      The long-term water flooding in oilfields leads to high water cut in oil wells, requiring environmentally friendly, low-cost, high-quality, and efficient chemical plugging agents for oilfield profile control. In this study, a thermoplastic flexible particle plugging agent was prepared by adding rubber powder. Experimental results showed that the rubber powder blended flexible particles had an appropriate particle size distribution and a porous structure. Compared to the particles without rubber powder, the rubber powder blended flexible particles exhibited higher thermal stability and better mechanical properties, including hardness, elasticity, cohesiveness, and recoverability. The flexible particles remained stable in high-temperature and high-salinity water, and exhibited good thermoplasticity by undergoing cohesion at high temperatures. Physical model experiments demonstrated that the rubber powder blended flexible particles could generate stable pressure difference fluctuations, quickly adapt to fractures’ deformation and pressure changes, and form effective plugging. In summary, the rubber powder blended flexible particles possess excellent deformability, thermal stability, and injection performance, making them suitable for addressing the problem of deep fluid diversion in oilfields and enhancing oil recovery.

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    • Research progress of foam system stabilized by nanoparticle for oil flooding

      LIANG Xiaotian, 张景楠, LI Bin, LI Meng, SHI Yan, WU Chao

      Abstract:

      The stability of conventional foam system is poor, and the nanoparticles were used to stabilize foam. This paper mainly focuses on the nanoparticle stabilized foam for oil flooding, the important achievements made by scholars in the process of foam formulation research are elaborated. According to the main components of the foam formula, it is summarized into three types, and the characteristics of different types nanoparticles in stabilizing foam are analyzed. It is pointed out that the current research and development of nanoparticles stabilized foam for oil flooding will develop towards diversity, functionality, high-performance, low-cost, environment-friendly, and recycling. Finally, it is proposed that many researches in the formula of nanoparticle stabilized foam for oil flooding are based on experiments, and further research is still needed on the micro mechanism of nanoparticle stabilized foam, to form parameters that can quantitatively describe the impact of foam stability, to achieve functional customization of the new foam system, and to apply foam systems with different functions to different reservoirs or different production fields.

      • 1
    • The flow law and liquid resistance effect of water-in-oil emulsion in porous media

      JIA Leilei, ZHONG Liguo, LUAN Zhengxuan, HU Changhao, WANG Goudong, GONG Yuning, SHANG Ce, LIU HAO

      Abstract:

      Highly colloidal and asphaltic crude oil easily forms a water-in-oil emulsion with the water phase under the shear action of the throat, producing a liquid resistance effect and plugging the formation, resulting in a severe drop in well production. The flow law and liquid resistance effect of water-in-oil emulsion within a complex porous medium influenced by crude oil viscosity, water content, and the emulsion particle size/throat diameter ratio were investigated using indoor core replacement experiments and microscopic pore flow simulation techniques. The results demonstrated that the water-in-oil emulsion's liquid resistance effect increased with increasing water content, resulting in a rise in the beginning pressure gradient. For high-viscosity crude oils, crude oil viscosity has a stronger effect on the emulsion start-up pressure gradient, but for low-viscosity crude oils, the degree of matching of emulsion particle size to throat size has a bigger effect on the emulsion start-up pressure gradient. The droplet liquid resistance effect has a stronger influence on emulsion particle size than the throat shear effect, resulting in a progressive rise in the particle size of the water-in-oil emulsion as it flows through the porous medium. The liquid resistance effect increases seepage resistance when the capillary number of a water-in-oil emulsion decreases. The mechanism and influencing elements of the liquid resistance effect of water-in-oil emulsion in porous media are clarified in this research, which gives a theoretical basis for improving recovery in highly colloidal and asphaltene reservoirs.

      • 1
    • Research progress on nanomaterials and nanocomposites for well cementing

      XIA Xiujian, YU Yongjin, QI Fengzhong, LI Changkun, XU Pu, LIU Huiting

      Abstract:

      The nanomaterial technology with rapid development has become a hot research and application topic in the field of oil and gas well cementing engineering. This article discusses the research and application progress of commonly used nanomaterials and polymer nanocomposites in the field of well cementing. Among them, nanoscale functional materials including silicon dioxide, zeolite powder, halloysite nanotubes, calcium carbonate, clay, magnesium oxide, alumina, carbon nanotubes/carbon nanofibers and grapheme have significant effects on improving the mechanical properties of set cement. However, their application is limited due to the difficulty of dispersing nanomaterials. Polymer latex, nanoemulsion and other organic nanoparticles can significantly improve the channeling prevention performance of cement slurry, the oil washing effect and flushing efficiency of preflush, and play an important role in ensuring the safety and quality of cementing. The modification technology of polymer nanocomposites has been extensively studied in terms of improving the temperature resistance and comprehensive performance of polymer cementing additives. Its comprehensive performance has been greatly improved compared to traditional polymers, and even significant technological breakthroughs have been made. The article proposes suggestions for the research and development of polymer nanocomposite used as cementing admixtures in response to major technical difficulties in complex deep and unconventional oil and gas well cementing. It also proposes product research and development routes from two aspects: nano surface grafting modification and nano intercalation technology, which have an important guiding role in the research and development of key cementing additives. It is expected to promote the progress of complex oil and gas well cementing engineering technology.

      • 1
    • Development and Application of a Nano Homogeneous Phase Retarded Acid System

      崔波, FENG Pu yong, YAO Er dong, RONG Xin ming, Wang Shun, ZHOU Fu jian

      Abstract:

      A new retarded acid system, nano homogeneous phase retarded acid was developed to solve the problems of high friction of emulsified acid and damage of gelled acid polymer residue in carbonate reservoir. The system consists of 20%HCL, 5% PA-NA nano emulsion, 0.1% drag reducer and functional additives. The properties of homogeneous phase retarded acid system were systematically analyzed and evaluated by means of rotating rock disc instrument, scanning electron microscope, EDS spectrometer, conductivity meter, particle size analyzer, interfacial tensiometer, wetting Angle tester, friction tester, acid erosion crack conductivity meter and core flow meter. The experimental results show that the homogeneous phase retarded acid system is a nano homogeneous dispersion system with oil in the inner phase and acid in the outer phase, and the particle size distribution is 8~100nm. It overcomes the disadvantages of high friction of emulsified acid and damage of thickened acid polymer residue, and has the properties of strong retarded speed (retarded rate greater than 90%), low friction resistance (lower resistance rate greater than 75%), low viscosity, low damage and high acid corrosion fracture conductivity. It can dissolve organic scale and inorganic scale at the same time (asphalt dissolution rate is greater than 5%, carbonate karst hydrolysis rate is 100%); It can remove the damage of reservoir emulsification, water lock and wetting modification. The homogeneous phase retarded acid system is adsorbed on the surface of positive electric limestone by negatively charged nano-emulsion to establish the "isolation barrier" of acid rock and achieve strong slow speed. Through differentiated acid erosion and viscous fingering, high acid erosion fracture diversion is realized. Through the special oil-water miscible structure of nano-emulsion, the organic scale and inorganic scale can be removed simultaneously. The successful application of this system in the field is of great significance for deep reservoir stimulation and multiple damage removal of carbonate reservoir.

      • 1
    • Prerparation and properties of an amphiphilic oil displacement polymer

      ZHANG Jing, CHEN Bin, SUYanhui, WANG Bin, KANG Lei, LIU Guanjun, XU Hao, WU Xiaoyan

      Abstract:

      The tertiary oil recovery technology in offshore oil fields faces severe reservoir conditions, such as high temperature, high salinity, and oil viscosity, while the platform space is very limited. This special working environment requires oil displacement polymers to have strong salt resistance, temperature resistance, long-term thermal stability, and rapid dissolution ability. Therefore, it is urgent to develop oil displacement polymers with good viscosity increasing and instant solubility performance. Based on the above objectives, an amphiphilic oil displacement polymer (HAP) was developed. A new type of HAP was prepared by using acrylamide (AM), acrylic acid(AA),2-acrylamide-2-methylpropanesulfonic acid (AMPS), and independently developed long-chain alkyl polyether based amphiphilic functional monomers (POM). The free radical aqueous solution polymerization was used for low-temperature initiation to prepare the HAP, and a high-performance polymer product was obtained through optimization of the synthesis process. Compared with commercially available temperature and salt resistant polyacrylamide, HAP solution exhibits outstanding temperature and salt resistance, shear resistance, and good long-term stability under simulated reservoir conditions. The core displacement experiment shows that the crude oil recovery rate of HAP polymer target fluid under simulated SZ36-1 oilfield conditions is 8.8 percentage points higher than that of commercially available temperature and salt resistant polyacrylamide with the same concentration.

      • 1
    • Development and performance evaluation of new foaming agent for foam fracturing of coalbed methane reservoir

      XI Baohua, LIU Dongna

      Abstract:

      Foam fracturing is a common technical means in the fracturing and stimulation of coalbed methane reservoir, and the selection of foaming agent is particularly important. In order to develop a foaming agent with better foam performance, lower cost and excellent comprehensive performance, a new foaming agent HBS-J was prepared from tea saponin, alkenyl succinic anhydride and sodium bisulfite through esterification and sulfonation reaction. Its structure was characterized by infrared spectrum, and its comprehensive performance was evaluated. The results show that the new foaming agent HBS-J has good foaming performance, salt resistance, oil resistance and surface activity. When the mass fraction of HBS-J is 0.3%, the comprehensive index of foam can reach 25193 mL · min, and the foaming ability and stability of foam are relatively strong; When the Na+ concentration in the saline solution is 79310mg/L, the Ca2+ concentration is 5405mg/L, the Mg2+ concentration is 2021mg/L or kerosene volume fraction reaches 25%, HBS-J can still form a relatively stable foam system, and its foaming ability, salt resistance and oil resistance are significantly better than traditional foaming agents. HBS-J also has good reservoir protection performance, and the damage rate to the permeability of coal bed matrix is less than 10%, so it will not cause serious damage to the coalbed methane reservoir during the foam fracturing construction. The research results show that the new foaming agent HBS-J can be used as a foaming agent for foam fracturing of coalbed methane reservoir.

      • 1
    • Research progress on integrated working fluid for fracturing, shut-in and back-flow

      XING Liang, DONG Zhengliang, ZHANG Yanjun, ZHANG Yanru

      Abstract:

      The goals of cost reduction and efficiency increase in the oil and gas industry, the demands for environment protection development, and the rapid development of integrated geological engineering technology have posed new challenges and requirements for wellbore working fluids. After the working fluids contact with the formation during the fracturing process, a series of physical or chemical reactions occur. It not only affects the effectiveness of hydraulic fracturing, but also closely relates to the process of shut-in and backflow after fracturing, thereby affecting the subsequent production of oil and gas wells. In addition, the different working fluid systems also faces some problems such as homogenization waste, functional singularity and physicochemical incompatibility. Therefore, clarifying the required characteristics and research status of the working fluids at each stage is of great significance for the development of integrated working fluids. Based on this, the characteristics that the working fluid needs to meet and current results in various stages such as fracturing, shut-in, and flowback are elaborated. The characteristics and research status for polymer, surfactant, foam and gas working fluids are emphatically described. By summarizing the characteristics of working fluids mentioned above, the discussion and outlook on integrated working fluids are conducted around three aspects: "synergistic effect of fracturing and extraction", "temporary plugging of fracturing to improve liquid energy efficiency", and "low-carbon, green integrated working fluids". The integrated working fluid involves a broad range of researches and techniques. It is necessary to strengthen the collaborative studies between multiple processes, which can provide a reference for the development and enhancement of the integrated working fluids during fracturing, shut-in and backflow.

      • 1
    • Fabrication and Degradation Test of Ammonium Persulfate Nanocapsules for Controlling Degradation Profile of Insoluble Residue in Slickwater

      PU Jingyang, LI Gensheng, SONG Xianzhi, LUO Sihui, WANG Bin

      Abstract:

      This study aims to investigate the key scientific and technical issues in the construction and thermal-triggered release of ammonium persulfate (APS)-entrapped nanocapsule breaker to precisely control the chemical breaking and degradation reaction between APS and polymers in a volume fracturing project of tight oil. The research focuses on studying the mechanism of hydrophobic polymers’ nano-precipitation on the interface of water-in-oil microemulsion droplets to construct the APS-entrapped nanocapsule breaker with sizes ranging from 215 to 355 nm. The polymers are motivated to precipitate onto the droplet which easily causes a polymer shell formation with low energy-consuming. The mechanism of pre-loaded Pluronic P-123 on the shell of the nanocapsules as “thermal switches” which can be triggered by environmental temperature is comprehensively investigated. Controlled-release behaviors of the APS nanocapsule breaker under different conditions via these switches have been studied. The APS nanocapsule can delay the degradation time of HPAM up to 24 hours. The research results provide a new way to solve the degradation problem of slickwater residual in complex network systems of tight oil, especially in the deep micron-sized fracture system.

      • 1
    • Study on the Efficiency of Microalgae-Bacteria Treatment of Oilfield Produced Water and Domestic Sewage

      PAN Jie, LI Tong, LI Ran, ZHAO Jin

      Abstract:

      The oilfield produced water and domestic sewage were mixed for microalgae-bacteria symbiotic culture. The effects of different mixing ratios (1/3, 1/5, 1/15, 1/35) on biological growth and nutrient removal were investigated. The experimental results showed that the growth of microalgae-bacteria was the best in the mixed solution of produced water/domestic sewage =1/3, and the total biomass reached 0.56 g/L, among which the density of algae was 0.33 g/L, the density of aerobic bacteria was 0.23 g/L, and the content of chlorophyll-A of algae reached 649.27 μg.(mg.DCW)-1. In terms of nutrient removal, the sewage with high mixing ratio is more conducive to the absorption of nutrients by microalgae and bacteria. When the mixture ratio of produced water and domestic sewage is 1/3, the removal rates of organic matter and ammonia nitrogen are the highest, the total COD removal rate is 65%, and the removal rate of ammonia nitrogen is 37%. The wastewater with a mixture ratio of 1/5 of produced water and domestic sewage has the best total phosphorus removal effect, and the removal rate reaches 70%.

      • 1
    • Synthesis and evaluation of high temperature microsphere fluid loss reducerMA chao1,2,3*,LIU yilin1,TANG jiajing1,ZHOU xu1,LIU chao1

      LIU Yilin

      Abstract:

      With Oil and gas exploration and development in deep and ultra-deep Wells has become the main way of strategic replacement of oil and gas resources, and drilling engineering has put forward higher requirements for the temperature resistance of fluid loss reducer in drilling fluids. β-cyclodextrin has a special rigid and stable structure of pyramidal ring and a special adsorption capacity of hydrophobic inside and hydrophilic outside. β-cyclodextrin was grafted with maleic anhydride, and organosilicone polymer 3-(trimethoxy-silicyl) methacrylate with excellent high temperature stability was introduced, and copolymerized with sodium p-styrene sulfonate and dimethyldiallyl amine chloride. A high temperature resistant microsphere fluid loss reducer (LY-1) was synthesized. The optimal synthesis conditions of the fluid loss reducer are: The monomer mass fraction was 25%, the initiator mass fraction was 1% of the monomer mass, the monomer mass ratio m(C8H7SO3Na):m(KH570):m(DMDAAC):m(MAH-β-CD) was 15:3:2:15, pH was 10, the reaction temperature was 75℃, and the reaction time was 4h. The total heat loss of the polymer is about 35.98% in the range of 284°C ~ 453 °C, and has good temperature resistance at 300 °C. After adding 3%LY-1 to the 4% sodium bentonite slurry and rolling at 200℃ for 16h, the filtration loss of the slurry decreased from 140mL to 12. The polymer has good filtration loss performance, but has little influence on the rheological property of the slurry.

      • 1
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    • YANG Mingjiao,LIN Zhangbi

      2019,36(1):188-190, DOI: 10.19346/j.cnki.1000-4092.2019.01.035

      Abstract:

      From the perspective of editorial practice,common problems in the major part of scientific paper,including abstract, introduction,experiments,result and discussion,conclusion,were analyzed. In order to improve the researchers’writing level,a method of using mind mapping to clear the writing thoughts was put forward.

    • DU lin,LIU wei,CHEN Xingyi,QING Xiaoyuan,REN Xuefei

      2019,36(2):367-372, DOI: 10.19346/j.cnki.1000-4092.2019.02.034

      Abstract:

      Diffusion of CO2 in oil phase plays an important in enhanced oil recovery,since its impact on the recovery improvement percentage and oil viscosity reduction percentage. The research progress on the CO2 diffusion coefficient measurement methods including direct method and indirect method,were summarized. The difference of mathematic models and research progress of indirect method were pointed out in this paper. Based on the summary,it is pointed out that the improving the analysis of impact factors,enriching the research dimension,and improving the study of diffusion law in different scale pores will become the focus and hotspot of the future.

    • ZHANG Rusheng1,WANG Zengbao2,3,ZHAO Mengyun1,LIU Changyin1,SUN Zhiyu1,JI Yuan2,ZHAO Xiutai2

      2019,36(2):225-229, DOI: 10.19346/j.cnki.1000-4092.2019.02.007

      Abstract:

      In order to reduce the damage to the reservoir caused by the leakage of fracturing fluid and the solid phase residue after breaking the gel,based on the shielding temporary plugging oil and gas layer protection theory and the characteristics of microcapsule breaker,the helper-breaking capsule type shielding temporary plugging protection agent in fracturing named TD-1was prepared by liquid drying method,which used organic acid as the core material,ethyl cellulose as the capsule material,polyethylene pyrrolidone as the porogen,and polyvinyl alcohol as the protective agent. The preparation condition was optimized and the performance of TD-1 was evaluated. The results showed that the main particle size of TD-1 was about 300 μm,the content of organic acid in coated core material was 34.1%,and the release rate was 69.0%,when TD-1 was synthesized under the condition of 2.0% polyvinyl alcohol,4.0% ethyl cellulose and polyvinyl pyrrolidone,and 500 r/min stirring rate. TD-1 was helpful for gel breaking of fracturing fluid,which could reduce the viscosity of fracturing fluid by 35.6% and the solid residue content by 44.9%. Meanwhile TD-1 had little effect on the viscosity of fracturing fluid and gel breaking time. TD-1 could form a temporary plugging zone on the surface of reservoir,which could reduce the invasion damage caused by the fracturing fluid filtrate and solid phase material. TD-1 improved the permeability recovery rate by 11.32% and made the core permeability recovery rate reached 82.47%,showing good effect on temporary shield plugging reservoir.

    • MA Jingyuan, PAN Yidang, YU Peizhi, AN Yuxiu

      2019,36(1):181-187, DOI: 10.19346/j.cnki.1000-4092.2019.01.034

      Abstract:

      From the aspects of amine inhibitors,nanocomposites and other inhibitors,the research status of new shale inhibitors at home and abroad and some inhibitor evaluation methods were reviewed. The inhibition mechanism of various inhibitors was analyzed. In general,the hydration expansion and dispersion of shale was inhibited by various inhibitors mainly from both chemical and physical aspects,thereby improving shale stability

    • ZHANG Wenzhe1,2,LI Wei1,2,WANG Bo1,2,LIU Yun3

      2019,36(2):191-195, DOI: 10.19346/j.cnki.1000-4092.2019.02.001

      Abstract:

      In order to speed up the development of tight oil and improve the horizontal well drilling technology of tight reservoir in Yanchang oilfield,meanwhile,aiming at the polyacrylamide potassium salt(K-PAM)polymer drilling fluid system used in the current stage of Yanchang oilfield had shortcomings such as poor rheology,insufficient plugging and inhibition,the indoor optimization of the commonly used fluid loss reducer,inhibitor,lubricant,plugging agent and other treatment agent was preferred to obtain a formula of strong plugging type nano-polymeric alcohol water-based drilling fluid suitable for tight reservoir. Finally,the drilling fluid was applied in the field. The results showed that the polymer fluid loss additive COP-FL could significantly improve the water loss and wall-forming property of the system. The non-fluorescent anti-collapse lubricant FT342 had strong inhibition. The liquid extreme pressure lubricant JM-1 had good overall lubrication effect. And blocking agent anhydrous polymeric alcohol WJH-1 and nano-emulsion RL-2 could increase the drilling fluid blocking rate by 51.7%,which could enhance the wellbore stability. The horizontal section strong plugging type drilling fluid system,whose formula was 4% sodium bentonite,0.2% soda ash,0.4% K-PAM,2% COP-FL,1.5% FT342,1.0% JM-1,5% WJH-1 and 3% RL-2,was applied to two horizontal wells in tight reservoir of Yanchang oilfield. During the construction process,the system had good leakage prevention and sealing effect. The mechanical drilling speed increased by 30% compared with the adjacent one,the construction period shortened by 35% ,the downhole accident rate reduced by 85.7%,and the drilling cost reduced by 34.7%,which provided effective technical support for the excellent drilling of horizontal wells in tight reservoir of Yanchang oilfield.

    • LIU Yi1,2,LUO Cheng1,LI Liangchuan1,2,WU Jun1,2,WU Zuohao1,YAN Fei1,2,DAN Jiamin1,2

      2019,36(3):394-399, DOI: 10.19346/j.cnki.1000-4092.2019.03.003

      Abstract:

      Aiming at the problem of gel nonuniform breaking using ammonium persulfate(APS)at fracturing fluid in Gaoshangpu oilfield,a gene fragment of β-mannan enzyme was extracted from marine thermophilous bacteria. The gel breaking principle of APS and biological enzyme was analyzed by means of GPC and electrospray ionization mass spectrometry. The proper temperature and the range of pH vale of β-mannan enzyme was researched. The fracturing fluid prepared with guar gum,biological enzyme,capsule breaker and other additives was applied in some deep wells of Gaoshangpu oilfield. The results showed that mannan enzyme was endonuclease. The viscosity and molecular weight of guar gum were greatly reduced by intersecting action which directly affected on the glycosidic bond and mainly produced 2—6 oligosaccharides with few monosaccharide. While APS preferred to break the C—C bond on the sugar ring. β-mannan enzyme tolerated 120℃ and 4—10.5 pH value. The optimum temperature was 70℃ and the pH value was 6—7. The enzyme activity at 120℃ was 40% of the highest enzyme activity,and the activity could maintain 55 min. While when the temperature was 90℃,the activity maintaining time increased to 180 min. Adding APS and biological enzyme into the fracturing fluid could reduce 22%—45% residue content. When the fracture was completely closed,the technology of injecting high concentration biological enzyme acquired effective stimulation in 9 fractured wells. The average injection pressure initially decreased about 13 MPa,the average cumulative injection quantity was 1.2×104 m3,and the validity was 290 days.

    • ZHANG Xiaogang,SHAN Haixia,LI Bin,ZHANG Yi,ZHOU Yaxian,WANG Zhonghua

      2019,36(2):196-200, DOI: 10.19346/j.cnki.1000-4092.2019.02.002

      Abstract:

      A new fluorescent-free biomass lubricant ZYRH was developed to overcome the disadvantages of high fluorescence level and poor thermal stability of commonly used lubricants. The fluorescence grade,emulsifying stability,lubricity,temperature resistance and salt resistance of ZYRH were studied. The effects of ZYRH on the rheology and wall building properties of drilling fluid were investigated. The results showed that the ZYRH level was less than 3,the stability of emulsification was good,the tolerance to temperature was up to 200℃,and the salt resistance was saturated. After adding 1% ZYRH lubricant to the base pulp, the decrease rate of the extreme pressure lubrication coefficient was 91.5%—93%,the biological toxicity EC50>1×106 mg/L. ZYRH was compatible with polymer drilling fluid,polysulfonate drilling fluid and microbubble drilling fluid. ZYRH was applied in 25 wells,such as Wei 455 well and Wen 23 gas storage,and achieved good results,and the product had no pollution to the environment.

    • WU Weipeng1,2,HOU Jirui1,2,QU Ming1,2,WEN Yuchen1,2,LIANG Tuo1,2,YANG Jinbin1,2,ZHAO Mengdan1,2

      2020,37(1):133-137, DOI: 10.19346/j.cnki.1000-4092.2020.01.023

      Abstract:

      The 2-D smart black nano-card is a new nanosheet material which is independently developed by the institute of enhanced oil recovery from china university of Petroleum(Beijing). The nano-card has the advantages of small size(80×60×1.2 nm)and large specific surface area(57 m2/g). In this paper,2-D smart black nano-card displacement experiments was carried out with different porosity and permeability two-dimensional visualized models. Through analyzing the influence factors such as core permeability, particle concentration and injection rate on oil displacement effect,the migration rules and microscopic seepage mechanism of the 2-D smart black nano-card system were studied. The experiment results revealed that the nano-card had advantage hydrophile-lipophile balance(HLB). The wettability of the rock surface could be changed,the wedge osmotic pressure could be generated by the two-phase interface,and the microscopic cyclotron could be formed. Besides that,nano-card had enormous surface contact compared with previous spherical nanoparticles such as SiO2. Therefore,nano-card could effectively displace the remaining oil from the formation,peel off the oil film on the throat wall on micro pores,expand the sweep volume of the low permeability layer,and thus,improve the degree of the crude oil recovery.

    • MA Zhenpeng1,LI Hui1,YANG Zhigang1,YU Tiantian2,MA Tianqi1,ZHANG Shuxia1

      2019,36(2):215-218, DOI: 10.19346/j.cnki.1000-4092.2019.02.005

      Abstract:

      Based on the analysis of the water quality characteristics of the guar gum fracturing flow-back fluid(GGFFBF)from acertain oil well in Yanchang oilfield,the process of water quality regulation-flocculation-O3 oxidation was carried out to treat the GGFFBF and the treated GGFFBF was reused to prepare the slick water fracturing fluid. The effects of various process parameters on the treatment effect were explored. The results showed that when adjusting the pH value of the 500 mL GGFFBF to 9.0 and adding 800 mg/L flocculant IF-A and 1.0 mg/L coagulant FA-B,and then pumping O3 for 40 min at a speed of 30 mL/min,the treated GGFFBF was colorless,clear and transparent,and the water quality was good. The SS content was less than 3.0 mg/L,the Feion content was below 0.5 mg/L,the viscosity was reduced to 1.28 mPa·s,and the bacterial content was low. The slick water fracturing fluid was prepared with the treated GGFFBF,and the performance of the slick water fracturing fluid was similar to that of the slick water fracturing fluid prepared with tap water,according with DB.61/T 575—2013 standard. The treated GGFFBF met the requirements for water preparation for slick water fracturing fluid.

    • FENG Xiaoyu1,2,3,HOU Jirui1,2,3,CHENG Tingting1,2,3,ZHAI Haoya1,2,3

      2019,36(2):280-285, DOI: 10.19346/j.cnki.1000-4092.2019.02.018

      Abstract:

      Nanoparticle flooding technology has a good oil displacement effect in low permeability reservoirs,but the problem of nanoparticles agglomeration in aqueous solution and blocking small pores in the formation has not been well solved. Low-cost oleic acid is used herein to surface modification of nano-TiO2 for reducing the agglomeration of nanoparticles,and the oil displacement system was optimized through low-permeability core simulation flooding experiment. The results showed that when the molar ratio of oleic acid to nano-TiO2 was 1∶1 and reacted at 60℃ for 4 h,the obtained modified nano-TiO2 had the longest stabilized dispersion time in aqueous solution. Infrared spectroscopy confirmed that the oleic acid group was successfully grafted onto the surface of nano-TiO2 . SEM and Zeta potential indicated that the dispersibility and stability of the modified nano-TiO2 particles was greatly improved. The particle size test results showed that the average particle size of nano-TiO2 in aqueous solution was 246.7 nm. the contact angle of unmodified nano-TiO2 and modified nano-TiO2 system with mass fracion of 0.05% on the surface of hydrophilic slide was 29.95o and 81.44 o,respectively,and the interfacial tension value was 0.475 and 0.74 mN/m,respectively,which explained the mechanism of enhancing oil recovery of the modified nano-TiO2 was still mainly relying on changing rock wettability and reducing oil-water interfacial tension. As for the low peameability reservoir with peameability of 9×10-3~12×10-3μm2,the reasonable injection parameters of the displacement system was 0.1% modified nano-TiO2+0.05% OP-10,and the reasonable injection volume was 0.3 PV,at this time,the enhanced oil recovery reached up to 15%. The nano-TiO2 solution could not only reduce the pressure of the injected water,but also improve the recovery rate of low-permeability core.

    • ZHANG Jingnan1,2,TIAN Lei3,ZHANG Hongwei1

      2021,38(1):184-190, DOI: 10.19346/j.cnki.1000-4092.2021.01.034

      Abstract:

      Nanofluid flooding is of great significance to reduce the cost of oil development and enhance oil recovery. A series of important results have been achieved about the research on the mechanism of nano-fluid flooding. This paper focuses on the basic research related to the nanofluid flooding mechanism. And the four mechanisms of nanofluid enhanced flooding are summarized based on the different academic opinions and research results. According to this,it is pointed out that under the combined effects of structural separation pressure,rock wetting change and reduced oil-water interfacial tension,the nanofluid exhibits the dual characteristics of“roll-up”and“diffusion”in the process of oil displacement,thus having enhanced oil displacement. Finally,it is pointed out that nanofluids will have a very broad application prospect in the field of enhancing oil recovery,but a lot of research is needed on the effect and influencing factors of nanofluid flooding. In addition,the effective combination of nanofluid flooding and foam flooding is a way to enhance oil recovery.

    • XU Yuande,GE Jijiang,SONG Longfei,ZHANG Yuhao,DU Xiaojuan

      2019,36(2):230-235, DOI: 10.19346/j.cnki.1000-4092.2019.02.008

      Abstract:

      In order to deal with the issue that high strength chromium gel always had high crosslinking speed,the formula of plugging agent was optimized by selecting cationic polymer and using of alumina sol. The chromium gel plugging agent suitable for deep profile control was developed and its performance was evaluated. The results showed that for acrylamide (AM)/ acryloyloxyethyltrimethylammonium chloride(DAC)binary copolymer organic chromium gel,the lower the cationic degree,the longer the gelation time was. Alumina sol could effectively delay the gelation time of cationic polymer chromium gel and improve its strength and long-term stability. The optimum formula of chromium gel system was 0.8% polymer Y5 with 5% cationic degree, 0.3% chromium acetate and 0.2% aluminum sol. The gelation time was 55 h at 90℃ and the elastic modulus was 16.6 Pa,which belonged to high-strength gel. The plugging agent had good injection ability and strong shear resistance. Meanwhile,it had strong temperature and salt resistance,and its blocking rate could reach more than 96%. This plugging agent had long gelation time and strong plugging performance,which could satisfy the requirements of deep profile control.

    • FAN Yue1,JIN Hao1,FANG Bo1,LU Yongjun2,QIU Xiaohui2,SUN Rui1

      2019,36(2):209-214, DOI: 10.19346/j.cnki.1000-4092.2019.02.004

      Abstract:

      To improve the thickening ability and crosslinkingperformance of cellulose,widen its application in fracturing fluid field,a new kind of hydrophobic etherifying agent(3-chloro -2-hydroxypropylerucylamideammonium acetate was prepared to modify carboxymethyl hydroxyethyl cellulose (CMHEC). Hydrophobic erucamidopropyl dimethylamine carboxymethyl hydroxyethyl cellulose (ED-CMHEC) was first prepared. The rheological and crosslinking experiments of CMHEC and ED-CMHEC were carried out. The results showed that ED-CMHEC solutions exhibited higher viscosities,more apparent thixotropy and viscoelasticity,compared to CMHEC solution. At the mass fraction of 0.3% ,the viscosity of CMHEC and ED-CMHEC solutions at the temperature of 30℃ and at the shearing rate of 170 s-1were 18.0 mPa·s and 71 mPa·s,respectively. The shear thinning behaviors of CMHEC and ED-CMHEC solutions at different concentrations could be well described by Cross model. Under the same crosslinking conditions that the dosage of zirconium organic crosslinker was 0.2%,the viscosity of gel formed by 0.3% ED-CMHEC solution was 2.4 times than that by 0.3% CMHEC solution,which indicated that ED-CMHEC had a stronger crosslinking performance.

    • HU Ting

      2019,36(2):277-279, DOI: 10.19346/j.cnki.1000-4092.2019.02.017

      Abstract:

      In view of the high concentration of hydrogen sulfide in water injection system of an oilfield in Bohai Sea,the modified triazine liquid desulfurizer and polyphosphate scale inhibitor were selected by measuring the desulfurization efficiency of desulfurizer on injected water and the effect of scale inhibitor on calcium ion concentration in injected water. Furthermore,the field pilot test was carried out on platform C where was the location of water injection well. The results showed that the desulfurization efficiency of modified triazine liquid desulfurizer for injected water was 98.1%,and the desulfurization effect was the best,but the concentration of calcium ion in water would reduce and scaling would occur. While used with polyphosphate scale inhibitor,the deposition of calcium ion could be significantly reduced. During the pilot test of the platform,the dosage of desulfurizer and scale inhibitor was 500 mg/L and 20 mg/L respectively. The concentration of hydrogen sulfide in the water source well system reduced from 800 mg/m3 to about 20 mg/m3,and the amount of hydrogen sulfide in the production fluid reduced from 150 mg/m3 to about 4mg/m3,which met the desulfurization requirement of the platform and avoided depositing scale.

    • ZHOU Quan1,LI Ping1,HA Junda2,WANG Li1,LV Hang1

      2019,36(2):240-244, DOI: 10.19346/j.cnki.1000-4092.2019.02.010

      Abstract:

      With the end of the block of polymer flooding area or the late effect,the dominant percolation channel is more prominent, and the difficulty of effective mining is increased. In view of the demand for fixed plugging in the deep fixed point after polymer flooding,in order to further tap the remaining oil and reduce the ineffective circulation of the injecting fluid in the process of production and development after polymer flooding,a low initial viscosity controllable gel plugging agent,composed of hydrolyzed anionic polymer with molecular weight of 25 million,metalion crosslinker,regulator,retarder,strengthening agent,was developed,and the performance of gel plugging agent system was evaluated. The results showed that the formulation of the system prepared with reclaimed wastewater was as follows,500—1000 mg/L polymer LH2500+1000—2500 mg/L cross-linking agent CYJL+200—500 mg/L regulator(citric acid)+ 100—150 mg/L retarder(sodiumsulfite)+ 100—200 mg/L enhancing agent(polyphosphate sodium),the initial viscosity of the system was low,being of within 10 mPa·s,and the gelation time was controllable within 10—30 days,and the gelling viscosity was above 2000 mPa·s. the tolerance to salinity was up to 20000 mg/L,and the suitable pH range was 8—9. The system has better core plugging performance,the blocking rate of the system to the core with the permeability of 0.48—3.9 μm2 was more than 99%,and the residual resistance factors was in range of 95.6—396.1.The results of the three-layer parallel core experiments indicated that the system had less pollution to the mid-low permeability core,meeting the in-sit plugging demand.

    • LIU Jing1,2,LIU Yi1,2,LI Liangchuan1,2,WANG Jinzhong1,2,ZHANG Xia1,2,TANG Cong1,2

      2019,36(2):271-276, DOI: 10.19346/j.cnki.1000-4092.2019.02.016

      Abstract:

      Aiming at the problems of rapid rising of water injection pressure and under-injection during the process of water injection in Gaoshangpu oilfield,a cationic-nonionic surfactant and pressure-lowering and injection-increasing agent JDZC was designed through the physical characteristics of low permeability reservoir in Jidong oilfield. The effects of JDZC dosage on surface tension,oil-water interfacial tension and emulsifying ability,and the temperature resistance,pressure-lowering and injection increasing ability of JDZC were studied. Finally,JDZC was applied in the field. The results showed that the temperature resistance of JDZC made from polyoxyethylene ether nonionic surfactant and rosin-based triquaternary ammonium salt could reach 130℃. With the increase of JDZC dosage,the surface tension of JDZC solution decreased and stabilized gradually. The surface tension of 500 mg/L JDZC solution was 28 mN/m. The critical micelle concentration of JDZC solution prepared with injected water in Jidong oilfield was 1000 mg/L. The minimum interfacial tension between 500—5000 mg/L JDZC solution and Jidong crude oil was maintained in the order of 10-2 mN/m. The emulsifying ability of JDZC to crude oil was good,and the larger the dosage,the stronger the emulsifying ability was. JDZC had obvious effect of reducing pressure and increasing injection for the core of Gaoshangpu main formation. The permeability of core after washing increased by 40% and the pressure decreased by 26%. The field application results of 38 wells showed that the field implementation efficiency was 94%,the initial injection pressure of water injection wells decreased by 8.5 MPa on average,the validity period was more than half a year,and the average enhanced injection of single well was more than 2×103 m3,which improved the water injection problem of Gaoshangpu low permeability reservoir.

    • SONG Jinbo1,WANG Lushan2,LI Changyou1,WU Mingming1,WEI Qingcai1

      2019,36(2):245-249, DOI: 10.19346/j.cnki.1000-4092.2019.02.011

      Abstract:

      The effective period of film-forming sand control agent depended on the molecular adsorption performance onto the surface of reservoir rock. In order to prolong the effective period of film-forming sand control agent,the adsorption performance of some cationic compounds onto the rock surface was simulated by combining molecular simulation with Monte Carlo method.According to the results of molecular simulation,the amphiphilc cationic polymer was designed and synthesized as a new film-forming sand control agent. The erosion resistance performance of film-forming sand control agent was studied,and it was implemented in Shengli oilfield. The results of simulation computation showed that hexane diacid monomer (HDA) and cyclohexane diamine monomer could not be well dissolved in water,but could be well dissolved in oil. HDA-DM1 polyamide chain had relatively good adsorption performance with -56.34 kcal/mol adsorption energy on the surface of quartz,indicating good thermal and mechanical performance. The core flooding experiment results showed that HDA-DM1 had good wash-resistant ability which was 3 times higher than that of standard requirement. The film-forming sand control agent was applied on 10 wells successfully,the sand control effect was obvious and the sand control life extended.

    • CHEN Fuming1,QU Yuan2,3,YU Haoyang1,YANG Yang1,FU Gaoqiang1,GUO Yufang4

      2019,36(2):201-208, DOI: 10.19346/j.cnki.1000-4092.2019.02.003

      Abstract:

      The volume expansion and separating water of submicron cement after solidification can not be explained by existing theories. In order to explore its mechanism,G-grade,ultra-fine and submicron cement slurry were cured at high temperature of 95℃ under sealed condition. Their deformation during hydration process had many similarities and obvious differences. It was concluded that in different hydration stages,the particles of hydration products in the slurry experienced the mutual exclusion, mutual pulling and mutual extrusion,which was the fundamental reason for the micro expansion,shrinkage,cracking,expansion, separating water and many other phenomena of the slurry in turn. On this basis,referring to the research results of other scholars,acement slurry hydration deformation model was constructed,which could provide a reasonable explanation for some phenomena.

    • KUAI Jingwen1,LU Xiangguo1,CAO Weijia1,CHEN Qing2,BAO Wenbo1

      2019,36(2):219-224, DOI: 10.19346/j.cnki.1000-4092.2019.02.006

      Abstract:

      In order to significantly reduce the preparation and transportation costs of existing fracturing fluid,and realize online preparation of sand-carrying fluid,a new type of self-thickening proppant was prepared by attaching guanidine gum powder onto the surface of proppant particles. Performance evaluation and reservoir damage experiments of the self-thickening proppant were carried out under experimental conditions of high-temperature and high-salinity reservoir environment. The results showed that under conditions of 80℃,compared with injection water of SZ36-1 oilfield,injection water of Changqing oilfield,sewage of Daqing oilfield and fresh water of Daqing oilfield,guanidine gum solution prepared by injection water of Dagang oilfield with the highest salinity had the best gel forming effect,the highest apparent viscosity,the largest energy storage modulus and the strongest sand carrying capacity. When the sand ratio was greater than 30%,the suspension time of the self-thickening proppant was less than 20 s and the settling time was greater than 4 h. When the dosage of the self-thickening proppant was 0.03%—5.0%,the gel breaking time was 14—2.5 h. In the constant velocity experiment,with the increase of core permeability,the filtration loss increased gradually and the damage rate decreased gradually. In the constant pressure experiment,with the increase of the filtration pressure difference,the filtration amount and the injury rate gradually increased. The self-thickening proppant could meet the need of fracturing construction in high-temperature and high-salinity reservoir,and had a a broad application prospect.

    • WANG Erzhen1,2,WANG Yong1,2,SONG Zhaojie1,2,DENG Zhiying1,2,WANG Weibo3

      2019,36(2):262-266, DOI: 10.19346/j.cnki.1000-4092.2019.02.014

      Abstract:

      Aiming at the problems of poor physical properties,high water injection pressure,increasing number of under-injected wells year by year and difficult treatment in Jiyuan oilfield,combining with the flow characteristics of small water volume and branched form in Changqing oilfield,a long-term on-line injection enhancement technology based on boosting water injection and medicament pressure control was proposed after analyzing characteristics of main blocks. Different types of booster devices with water injection capacity of 100—300 m3/d were installed in the well site,and comprehensive depressurization and injection agents were added to meet the demand of water injection. The pressure prediction chart of main blocks was established and applied in Jiyuan oilfield. The results showed that the booster met the local on-line boosting and injection requirements. The comprehensive agent COA-2 for water injection wells with stripping dispersant,chelating agent,wetting agent,cleaning agent,acidizing corrosion inhibitor and methanol as the main agents,had the advantages of anti-swelling,scale inhibition and reducing oil-water interfacial tension,and good effect of pressure control and injection boosting. The pressure prediction chart of the main block provided a basis for effectively controlling the rise of pressure. A total of 48 well groups were implemented in the oil production plant,which improved the under-injection problem of 105 wells with ineffective multi-round injection stimulation. The average validity period was 266 days,the average single well daily injection increased by 11 m3,and the cumulative injection amount increased by 54.95×104 m3. In the corresponding 826 oil wells,234 oil wells were effective with 2.25 t daily oil increase for average single well group,and 1.95 × 104 t cumulative oil increase,which reached the purpose of long-term stable water injection for multi-rounds ineffective injection wells.

    Editor-in-Chief:ZHANG Xi

    Founded in:1984

    ISSN: 1000–4092

    CN :51–1292/TE

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