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.
- Current Issue
- Online First
- Just Accepted
- Most Download Archive
-
GUO Chunping, JIANG Guancheng, GUAN Jintian, GUO You, HE Yinbo, YANG Lili, DONG Tengfei
2024,41(4):571-578, DOI: 10.19346/j.cnki.1000-4092.2024.04.001
Abstract:
Conventional water-swelling gels lack re-crosslinking ability,making them susceptible to displacement from loss zones under pressure fluctuations,which reduces their pressure resistance and leads to poor plugging performance. Aiming at these problems,a self-healing gel was synthesized using chitosan as a physical crosslinker,combined with acrylamide(AM),acrylic acid(AA)and stearyl methacrylate(SMA)monomers. The gel’s structure was characterized through infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy. Its swelling capacity,rheological properties,self-healing ability, compatibility with base fluid,and plugging performance were also investigated. Furthermore,the self-healing mechanism and plugging mechanism of the gel were analyzed. The results showed that the gel exhibited a spongy dual-network structure,with multiple non-covalent interactions including hydrogen bonding,electrostatic forces and hydrophobic associations within the network. The gel showed excellent water-swelling properties, which enhanced with increasing temperature. The swelling equilibrium value at 120 ℃ was 37 times higher than that at room temperature. After self-healing at 90 ℃,the gel particles exhibited a high storage modulus(3500 Pa)and a structural recovery rate(83%),while maintainined self-healing properties at 120 ℃. The compatibility between gel particles and base fluid was good. As the concentration of gel particles increased,the apparent viscosity of base fluid rose,while the fluid loss decreased. At a mass-volume ratio of 2%,the gel could meet the plugging requirements during drilling porous loss zones with simulated sand particles greater than 20 mesh(0.85 mm). The self-healing mechanism of gel primarily relied on non-covalent bonds in its network structure,which broke and re-formed rapidly after damage, restoring the gel’s integrity and functionality. In terms of plugging mechanism,the gel particles migrated,accumulated and compressed within the loss channels,forming tight contact with the formation. The non-covalent interactions enabled self-healing and strong bonding with the formation,creating a durable gel-plugging layer. This self-healing gel showed potential application in enhancing drilling fluid loss control.
-
WANG Chunsheng, ZHU Jinzhi, ZHANG Zhen, ZHANG Shaojun, WU Xiaohua, LUO Xiao, LI Qiang
2024,41(4):579-587, DOI: 10.19346/j.cnki.1000-4092.2024.04.002
Abstract:
Sulfonated treatments commonly used in deep-well water-based drilling fluids have significant biotoxicity without exact sources,which lead to the restriction of environmental protection regulations. To solve this problem,the relationship between the physicochemical characteristics of typical sulfonated treatments,such as functional groups,content of heavy metals and organic poisons,particle morphology,and their biotoxicity was analyzed. The results showed that the sulfonic acid groups in agents were not biotoxic,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-soluble components using a Soxhlet extractor made 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,the sulfonated agent was depolymerized using a homemade MOF. When replacing the sulfonated treatment agent in the sulfonated drilling fluid with the biologically non-toxic treated agent,the rheological properties of the drilling fluid were basically unchanged,the API and HTHP filtration loss only increased slightly. The sulfonated drilling fluid system realizes biological non-toxicity,which provide a powerful technical support for the application of sulfonated treatments.
-
HU Yaotai, XIANG Nan, LIU Kai, ZHANG Yan, ZHANG Lanlan, YAN Siming, LI Xinliang
2024,41(4):588-595, DOI: 10.19346/j.cnki.1000-4092.2024.04.003
Abstract:
With the deepening of oil well drilling,conventional drag reduction can no longer meet the performance and environmental protection requirements of cementing cement under new working conditions. An environmental polycarboxylate oil well cement drag reducer (HZ-1) was synthesized through free radical polymerization reaction using polycarboxylate superplasticizer polyether(TPEG-2400),sodium methacrylate sulfonate(SMAS),acrylic acid and other raw materials. The optimum synthesis conditions were optimized through orthogonal experiments. The structure and thermal stability of HZ-1 were analyzed by infrared spectroscopy, nuclear magnetic resonance hydrogen spectroscopy, thermogravimetric analysis and synchronous thermal analyzer. Indoor evaluation of the drag reduction,temperature resistance and environmental protection of HZ-1 was conducted according to the standards of oil and gas industry. The drag reduction mechanism of HZ-1 was explored through the changes in adsorption capacity,steric hindrance and Zeta potential. The results showed that the optimum preparation conditions for HZ-1 were obtained as follows:10 g SMAS,0.41 g sodium hypophosphite,175 g TPEG-2400,7.6 g hydrogen peroxide,0.91 g ascorbic acid,22.22 g acrylic acid,20 g 20% sodium hydroxide,dropwise addition time of 2.0 h,reaction temperature of 20 ℃,and reaction time of 0.5 h. HZ-1 had good thermal stability and a decomposition temperature of 338 ℃. The cement slurry system prepared by mixing 0.40% HZ-1 with oil well cement at a water cement ratio of 0.44 had good drag reduction performance,the flowability index of 1.033,the consistency coefficient of 0.023 Pa · sn,the compressive strength of 18.413 MPa,and the temperature-resistance capacity up to 170 ℃. HZ-1 had good biodegradability and environmental protection. Its EC50(half effective concentration)was 36 307 mg/L,COD(chemical oxygen demand)was 571 984 mg/L,and BOD5(biochemical oxygen demand)was 196 330 mg/L. The ratio of BOD5/COD was 0.3432. So the biological grade of HZ-1 was non-toxic. The greater the steric hindrance of HZ-1,the better the rheological property of cement slurry was. The adsorption curve of HZ-1 on the surface of cement particles met the Langmuir adsorption model,which was the chemisorption of single molecular layer. HZ-1 reduced the Zeta potential on the surface of cement particles and enhanced its electrostatic repulsion,thus enhancing the rheological properties of cement slurry.
-
LIU Weihong, WANG Xiaoliang, HU Qianhong, XU Mingbiao
2024,41(4):596-601, DOI: 10.19346/j.cnki.1000-4092.2024.04.004
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 polyaryl ether ketone high-temperature resistant resin powder was selected as elastic material and 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 0.80 Pa · sn,the filtration loss was 34 mL,the thickening time was 225 minutes,and the compressive strength was 17.69 MPa. The conventional performance of the cement slurry met the requirements of in-site operations. The elastic modulus of cement stone could be reduced to below 4 GPa, indicating that the addition of resin powder could improve the elasticity of cement stone. After curing for 28 days at the high-temperature of 320 ℃,the compressive strength of cement stone was 18.68 MPa,the impact strength was 1.97 kJ/m2,and the elastic modulus was 3.67 GPa,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 could effectively enhance the ability of cement stone to resist thermal stress damage during steam injection operations in thermal recovery wells.
-
PU Jingyang, LI Gensheng, SONG Xianzhi, LUO Sihui, WANG Bin
2024,41(4):602-609, DOI: 10.19346/j.cnki.1000-4092.2024.04.005
Abstract:
To against the backdrop of volume fracturing in tight oil formations,the study aimed to precisely regulate the degradation reaction of slickwater in distal micron sized or nano-sized fractures using ammonium persulfate(APS)as a breaker. It focused on the influencing factors in the construction and release control of thermal-controlled APS nanocapsule breakers. Using poly(methyl methacrylate)(PMMA),dichloromethane(DCM),Span 80,cyclohexane(CYH),triblock copolymer(Pluronic P-123)and APS as raw materials,APS droplets were encapsulated through the interfacial chemical action of hydrophobic polymer wall materials in a W/O inverse microemulsion,forming nanocapsule breakers. The preparation conditions for the nanocapsule breakers were optimized,and then the mechanism of controlled APS release and partially hydrolyzed polyacrylamide(HPAM)degradation by thermal-controlled nanocapsule breakers was analyzed by measuring the APS release rate at different temperatures and the viscosity retention rate of HPAM in simulated slickwater. The results showed that the optimum preparation condition of nanocapsule breakers was obtained as follows:50 ℃ reaction temperature,1∶1.5 volume ratio of DCM and CYH,100 mg Pluronic P-123,200 mg PMMA,10% mass fraction of APS in the core material,and 1∶1 volume ratio of Span 80 and APS solution. The nanocapsule breakers had an average particle size of 221 nm,good sphericity,and a theoretical shell thickness of 13 nm,with an APS loading rate of 78%. By utilizing the oxidative degradation characteristics of APS on the temperature-sensitive surfactant Pluronic P-123 at specific temperatures(60—80 ℃),a“thermal control switch”for the nanocapsule shell was preset,enabling precise regulation of APS release. The degradation times for HPAM in slickwater at 60 ℃ and 80 ℃ were 24 hours and 12 hours,respectively. The research findings provided a new approach to addressing the bottleneck of degradation and removal of slickwater residue blockages in complex fracture networks,especially in the distal secondary micro-fracture systems of horizontal wells undergoing volume fracturing in tight oil formations.
-
2024,41(4):610-615, DOI: 10.19346/j.cnki.1000-4092.2024.04.006
Abstract:
Foam fracturing is a common technical mean in the fracturing and stimulation of coalbed methane reservoir. 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,the foaming agent(HBS-J)was prepared from tea saponin,alkenyl succinic anhydride and sodium bisulfite by esterification and sulfonation. The structure of HBS-J was characterized by infrared spectrum,and then the foaming property,salt and oil resistance,surface activity,and reservoir protection of HBS-J were evaluated. The results showed that HBS-J had good foaming performance,salt and oil resistance,and surface activity. When the mass fraction of HBS-J was 0.3%,the foaming volume was 590 mL,the half-life of foam was 2562 s,and then the composite index of foam could reach 25 193 mL min,indicating strong foaming ability and foam stability. When the mass concentrations of Na+,Ca2+ and Mg2+ in brine solution were 79 310,5405 and 2021 mg/L respectively or the volume fraction of kerosene reached 25%,HBS-J could still form a relatively stable foam system. Furthermore,its foaming ability and salt and oil resistance were significantly better than those of traditional foaming agents,such as sodium dodecyl sulfate,sodium α-olefin sulfonate,coconut amidopropyl betaine. When the mass fraction of HBS-J was 0.25%—0.35%,the surface tension of solution(about 40 mN/m)was relatively low. The reservoir protection performance of HBS-J was good. The damage rate to the permeability of coalbed matrix was less than 10%. It would not cause serious damage to the coalbed methane reservoir during foam fracturing construction. HBS-J met the requirements of coalbed methane reservoir foam fracturing construction on the comprehensive performance of foaming agent.
-
CUI Tianyu, LU Xiangguo, GAO Jianchong, HE Xin, LIU Jinxiang, SUN Huiru
2024,41(4):616-623, DOI: 10.19346/j.cnki.1000-4092.2024.04.007
Abstract:
After long-term water injection and polymer injection development in Bohai L,S and J oilfields,the heterogeneity of reservoir is further enhanced. The polymer is retained in the reservoir,resulting in a significant decrease in liquid absorption capacity of the reservoir. Plugging removal is one of the most effective technical means to alleviate the current situation. In order to meet the needs of chemical flooding plugging removal technology in Bohai Sea,the plugging removal effect of compound plugging removal agent and scale dissolving agent composed of depolymerization agent,acid and chelating agent was evaluated. The influence and mechanism of injection mode,injection pressure and profile control measures on plugging removal effect were explored. The results showed that when the mass fraction of depolymerization agent composed of 1.0% ammonium persulfate and 0.5% inorganic corrosion inhibitor was 1.0% and the slug size was 0.05 PV,the permeability recovery rate of polymer-blocked core could reach 90.31%,indicating good depolymerization effect. When the mass fraction of scale dissolving agent composed of 0.54%citric acid and 5.46% chelating agent was 6.0% and 8.0%,the permeability recovery rate of three kinds of inorganic scale plugging cores was more than 80%,indicating good scale dissolution effect. Improving the injection rate of plugging removal agent could increase the injection pressure and improve the plugging removal effect. When the injection pressure increased to 3.0 times and 3.5 times the water flooding pressure,the recovery rate increased by 0.74 percentage point and 0.88 percentage point. However,after increasing the injection pressure,most of the liquid would still enter the high permeability part of reservoir,and then the increase of liquid absorption in low permeability layer was very limited,which would affect the plugging removal effect. Therefore,the combined operation technology of profile control and plugging removal was put forward. That is,profile control was carried out before plugging removal. Compared with simple plugging removal,when 0.3 PV and 0.6 PV inorganic gel profile control agent were injected,the recovery rate of profile control and plugging removal combined operation increased by 7.7 percentage points and 12.19 percentage points,respectively.
-
YAN Xiang, DAI Caili, LIU He, MENG Siwei, JIN Xu, WU Yining
2024,41(4):624-631, DOI: 10.19346/j.cnki.1000-4092.2024.04.008
Abstract:
Imbibition is a crucial approach for improving oil recovery in tight reservoirs. A shut-in strategy is usually adopted to enhance oil recovery by imbibition after fracturing,and chemical agents such as surfactant and nanomaterials are used to improve imbibition efficiency. However,the enhanced oil recovery(EOR)mechanisms of different types of imbibition agents need be distinguished and explained. In this study,four types of imbibition agent systems were employed to conduct imbibition experiments,including silica nanofluid and pure water with high interfacial tension(IFT)(?30 mN/m),pure surfactant solution with medium IFT(1—10 mN/m)and surfactants compound system with ultra-low IFT(<10-3 mN/m). The results showed that,as for the silica nanofluid and pure surfactant solution,the wettability alteration was the main EOR mechanism to improve the imbibition recovery in oil-wet reservoirs. Furthermore,the pure surfactant system could reduce the IFT and increased the deformability of oil droplets when the droplets passed through the pore throat. Therefore,the Jamin effect was alleviated,and the possibility of the oil droplets being snapped off and retained in the pore space is reduced,thereby improving the utilization degree of unrecovered oil. Nevertheless,the recovery results indicated that IFT reduction had a limited impact on the recovery enhancement,and that wettability improvement was more significant for improving recovery than IFT reduction. However,in the strong oil-wet pores,when the improvement of wettability was not effective and capillary force could not work ,the surfactant compound system exhibited the best imbibition performance. The ultra-low IFT between oil and water favored the spontaneous emulsification of oil,and changed the imbibition pattern from capillary force-driven imbibition to gravity-driven imbibition,and the emulsions formed spontaneously were drained out from the pore under the effect of gravity. The gravity-driven imbibition, which relies on the ultra-low IFT to promote the spontaneous emulsification of crude oil,provides a novel approach for enhancing imbibition recovery.
-
ZHANG Jing, CHEN Bin, SU Yanhui, WANG Bin, KANG Lei, LIU Guanjun, XU Hao, WU Xiaoyan
2024,41(4):632-639, DOI: 10.19346/j.cnki.1000-4092.2024.04.009
Abstract:
In order to improve the temperature,salt and shear resistance of polymer oil displacement agents,an amphiphilic oil displacement polymer (HAP) was synthesized by free radical aqueous solution polymerization and low temperature induced methods,using acrylamide(AM),acrylic acid(AA),2-acrylamide-2-methylpropanesulfonic acid(AMPS),and independently developed long-chain alkyl polyether amphiphilic functional monomer(POM)as raw materials. The optimum reaction condition was determined by examining the intrinsic viscosity and viscosity enhancement of HAP. The solubility,viscosity enhancement, shear resistance,salt resistance,long-term stability,and oil displacement performance of HAP were studied,and then compared with those of commercially available temperature and salt resistant polyacrylamide. The results showed that the optimum synthesis condition for HAP was obtained as follows:20% total monomer mass fraction,0.4%—0.8% POM dosage of total monomer mass, 8% AMPS,0.1%—0.4% initiator,and 0 ℃ initiation temperature. 0.175% HAP solution was prepared by simulating Bohai Sea seawater. The dissolution time of HAP was 30 minutes at 75 ℃,and then the apparent viscosity was 55.8 mPa s. At 75 ℃,0.175%HAP exhibited good shear resistance,salt resistance,stability and oil displacement effect. The viscosity retention rate of HAP solution was 27.8% when the shear rate increased from 7.34 s-1 to 100 s-1. When the salinity of simulated seawater increased to 30 g/L,the viscosity of HAP solution was 75 mPa s. After aging at 75 ℃ for 90 days,the viscosity of HAP solution became 36 mPa s. The core displacement experiment results showed that the final recovery rate of 0.175% HAP solution was 8.8 percentage points higher than that of commercially available polyacrylamide with temperature and salt resistance. The synthesized quaternary copolymer HAP exhibited excellent solubility,viscosity enhancement,shear resistance,salt resistance,long-term temperature stability,and high crude oil recovery rate,with better performance than commercially available temperature and salt resistant polyacrylamide.
-
LIU Yuelong, LIU Yiheng, YE Shuangxiang, DENG Xuefeng, QIANG Xing, WEI Kaipeng, ZHANG Hao, YANG Yang
2024,41(4):640-645, DOI: 10.19346/j.cnki.1000-4092.2024.04.010
Abstract:
The Chang 8 ultra-low permeability reservoirs of Honghe Oilfield suffer from high water flooding pressure and low oil-displacement efficiency. Chemical flooding could be a method to enhance the oil recovery in Chang 8 ultra-low permeability reservoirs. However,the adaptability of flooding agents in reservoirs is not clear. Therefore,the interfacial activity,pressure reducing and oil displacement ability of three types flooding agents,including surfactant,nano emulsion,and a silica nanofluid, were comparatively studied and their adaptability in Chang 8 ultra-low permeability reservoirs was analyzed. The results showed that the pressure-reducing rates of the 0.3% surfactant AMS,0.5% nano emulsion LIE,and 0.3% the silica nanofluid were 15.1%, 5.8% and 9.1%,respectively,under single-phase seepage conditions. The surfactant exhibited the highest pressure-reducing rate, which resulted from its superior wettability alteration ability. The wettability of rock changed from intermediate-wet to weak oil-wet under the effect of the surfactant. In contrast,the surfactant could not achieve pressure-reducing under two-phase seepage conditions because the surfactant could not inhibit the formation of oil-in-water emulsions. Meanwhile,the nano emulsion LIE and the silica nanofluid ASN exhibited favorable pressure-reducing performance due to their interfacial tension reducing ability and oil-in-water emulsion inhibition ability. The nano emulsion exhibited the highest pressure-reducing rate,being of 38.6%,because the interfacial tension reducing ability of the nano emulsion was better than that of the silica nanofluid. In nature core flooding experiments,the surfactant,the nano emulsion,and the silica nanofluid achieved enhanced oil recovery of 26.67 percentage point, 23.51 percentage point and 16.35 percentage point,respectively. The surfactant exhibited the best enhanced oil recovery ability. However,considering that the surfactant could not achieve pressure-reducing effect under two-phase seepage conditions,the nano emulsion was the best alternative for chemical flooding in Chang 8 ultra-low permeability reservoirs.
-
XIAO Lixiao, HOU Jirui, SUN Jiaqi, YUAN Weifeng, LIANG Tuo
2024,41(4):646-655, DOI: 10.19346/j.cnki.1000-4092.2024.04.011
Abstract:
The adsorption and retention of nanofluids on the surface of porous media are critical factors influencing the oil recovery enhancement in unconventional oil and gas recovery by nanotechnology. As a kind of amphiphilic sheet nanomaterials,it is necessary to study the dynamic adsorption laws of nanosheet in the cores. Firstly,the standard curve of nanosheet fluid was plotted and then the static adsorption experiment was carried out to clarify the concentration at which it reached adsorption saturation. On this basis,the dynamic adsorption experiments of nanofluids with different influencing factors were carried out. Afterwards,the variation laws of dynamic adsorption capacity were investigated by single-factor analysis and multi-linear regression method,and then the regression equation of dynamic adsorption capacity was established. The results showed that the saturation adsorption concentration of the nanofluid was 75 mg/L,while the maximum static adsorption capacity was 1.83 mg/g. The dynamic adsorption capacity had a negative logarithmic correlation with the permeability of low permeability cores(K),a negative linear correlation with the fluid mineralization ratio(MS),and a positive linear correlation with the injection slug of nanofluid(V2),as well as the injection rate(v)of the subsequent water flooding. The multiple linear regression equation between the dynamic equilibrium adsorption capacity( η2 )and K,MS,v and V2 of the nanosheet fluid in the low permeability core was obtained as follows: η2 = 10-3(-0.4 - 0.005 K - 0.094 MS + 1.301 v + 3.347 V2) ,with R2=0.989. Under the condition of 20×10-3 μm2(K),2(MS),0.3 mL/min(v),and 0.5 PV(V2),the dynamic adsorption capacity of the nanosheet was 1.328×10-3 mg/g by regression equation,closing to the experimental result(1.321×10-3 mg/g). Maintaining a moderate salinity range(MS<4),adjusting the slug level of nanofluid (0.5 PV),and reducing the injection rate of water flooding(<0.45 mL/min),could mitigate the dynamic adsorption capacity, which was beneficial to further improve oil recovery in low-permeability reservoirs.
-
GAO Yanbo, FAN Hui, WANG Fang, ZHOU Juan, WANG Xiaoye, DONG Xianpeng, LU Licheng
2024,41(4):656-663, DOI: 10.19346/j.cnki.1000-4092.2024.04.012
Abstract:
In the environment of high salt and low permeability reservoir,the dispersion stability of molybdenum disulfide(MoS2) nanosheet is poor,so it is often necessary to play a synergistic effect with surfactant to improve its performance. It is very important to clarify the interaction between MoS2 and surfactant to improve the application range of MoS2. By hydrothermal method,MoS2 nanosheets were synthesized with thioacetamide as sulfur source and molybdenum trioxide as molybdenum source. The effects of five surfactants on the dispersion stability of MoS2 nanosheets in saline was studied, and then the cationic surfactant hexadecyltrimethyl ammonium bromide (CTAB) was selected. The interfacial performance,emulsification properties and oil recovery effect of CTAB-MoS2(mass ratio of 10∶1)were investigated. The results showed that MoS2 nanosheet had layered structure,meanwhile the dispersion stability in deionized water was good. However,the dispersion stability decreased with increasing NaCl mass concentration. CTAB could significantly improve the dispersion stability of MoS2 nanosheets in 3000 mg/L NaCl solution. When the mass fraction of MoS2 was 0.1%,the addition of CTAB could increase the stabilization time of MoS2 from less than 3 h to 12 h. When the mass fraction of MoS2 was 0.005%,CTAB could reduce the average particle size of MoS2 from 122.7 nm to 98.1 nm,meanwhile the absolute Zeta potential value increased from 25.0 mV to 33.8 mV. 0.05% CTAB-0.005% MoS2 could spontaneously form a strong interface membrane and climbing membrane at the n-heptane/water interface. Furthermore,it could not only reduce the interface tension between n-heptane and water to 0.175 mN/m,but also have a good emulsifying effect. Based on its excellent salt tolerance and good interface activity,CTAB-MoS2 had certain enhanced oil recovery effect in low permeability environment. Under the condition of 60 ℃ and 3000 mg/L NaCl solution,when 0.5 PV 0.05% CTAB-0.005% MoS2 was injected into a low permeability(48.33 × 10-3 μm2)core,the oil recovery was enhanced by 9.85 percentage points. The construction of CTAB-MoS2 with high dispersion stability was expected to provide a solution for the efficient development of low permeability fields,and also provided research ideas for improving the dispersion stability of nanomaterials.
-
JIA Leilei, ZHONG Liguo, WANG Guodong, HU Changhao, GONG Yuning, SHANG Ce, LUAN Zhengxuan, LIU Hao
2024,41(4):664-670, DOI: 10.19346/j.cnki.1000-4092.2024.04.013
Abstract:
Crude oil containing natural active substances,such as resinous and asphaltenes,readily formed a water-in-oil emulsion under throat shear,leading to liquid resistance,formation plugging,and significant reductions in oil well production. This study employed core replacement experiments and microscopic pore flow simulations to examine the flow behavior and liquid resistance of water-in-oil emulsions in complex porous media,focusing on crude oil viscosity,water content,and the size ratio between emulsion droplet and throat. The results showed that increasing water content heightened the liquid resistance effect of water-in-oil emulsions,thereby elevating the threshold pressure gradient. Under the condition of 550 mPa·s crude oil viscosity,20%—50%water content,and 300×10-3 μm2core permeability,the threshold pressure gradient of water-in-oil emulsion was 12—37 MPa/m. For high-viscosity(550 mPa·s)crude oil,viscosity significantly influenced the emulsion threshold pressure gradient,while for low-viscosity(<30 mPa·s)crude oil,the droplet-to-throat size ratio had a more pronounced effect. Due to the liquid resistance effect,water droplets accumulated at the throat inlet,leading to agglomeration and the formation of larger droplets within the water-in-oil emulsion. A larger emulsion droplet-to-throat diameter ratio increased the seepage resistance of dispersed phase(water droplets). A decrease in the capillary number of water-in-oil emulsion increased seepage resistance due to the liquid resistance effect. Calculations showed that when the capillary number was 9.9×10-4(low-viscosity crude oil)and the ratio of droplet size to throat diameter was 2.5 or 10.0,the liquid resistance effect increased the seepage resistance of water-in-oil emulsion through the throat to 7 or 35 times that of pore flow resistance. The results clarified the liquid resistance effect of water-in-oil emulsion flow in porous media and its influencing factors,providing theoretical guidance for the study of formation crude oil seepage and enhanced oil recovery.
-
JIA Junhong, FAN Wei, LI Mei, DAI Shanshan, QIN Sen, YANG Jialong, WANG Ruiyao
2024,41(4):671-679, DOI: 10.19346/j.cnki.1000-4092.2024.04.014
Abstract:
In this work,molecular simulation was introduced into the design of molecular structure and the study of mixing mecha-nism of miscible flooding agent,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 agent 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 agent,was comprehensively evaluated in combination with the diffusion coefficient. The results showed that increasing the number of CO2-philic groups synergized with the appropriate spatial site resistance was beneficial to enhance the miscible flooding effect.
-
SHI Xin, XU Yanyan, WU Yajun, WU Beibei, XI Linghui, HOU Baofeng
2024,41(4):680-685, DOI: 10.19346/j.cnki.1000-4092.2024.04.015
Abstract:
Research on the mechanism by which surfactants change the wettability of rock surfaces has certain theoretical guiding significance for on-site construction in oilfield. The wettability changing mechanism of oil-wet sandstone surface by anionic surfactant sodium lauryl alcohol polyoxyethylene ether sulfate-1(PES)was studied through the determination of infrared spectrum, morphological scanning imaging,Zeta potential,solid surface oscillation frequency and contact angle. The results showed that compared with the infrared spectrum of oil-wet quartz powder,the infrared spectrum of quartz powder treated with PES had stretching vibration peaks of S—O bond,sulfoxide S=O bond and sulfone —SO2— bond,indicating that“adsorption”was the wettability changing mechanism of oil-wet sandstone surface by PES. Due to the adsorption of PES on the surface of oil-wet quartz wafer,the surface of quartz wafer was relatively flat and the average roughness was greatly reduced. The Zeta potential of untreated oil-wet quartz particles was -4.2 mV. The Zeta potential value of the sample treated with PES decreased with the increase of PES concentration,and finally tended to equilibrium. The electrostatic repulsion force between PES and negatively charged rock surface made PES adsorb on the sandstone surface with weak intermolecular force. As the concentration of PES increased,the resonance frequency decreasing amplitude of quartz crystal surface became larger and larger,that was,the adsorption amount of PES molecules on the rock surface became larger and larger. In addition,the original contact angle of untreated oil-wet quartz wafer was 140° ,while the corresponding contact angle of oil-wet quartz wafer treated with PES was 109° . With the addition of PES,a double-layer adsorption structure formed between the hydrophobic chain of surfactant and the hydrophobic end of crude oil components. At this time,the hydrophilic head group of surfactant exposed outside,making the contact angle gradually decrease, thus changing the wettability of solid surface.
-
2024,41(4):686-694, DOI: 10.19346/j.cnki.1000-4092.2024.04.016
Abstract:
Aiming at the problems of poor flooding effect of water flooding,polymer flooding in high recovery degree and ultra-high water cut stage of high-temperature reservoir,anionic surfactants and cationic surfactants were used in combination,and an in-situ emulsification flooding system composed of 1500 mg/L polymer P5 + 0.3% surfactant S-2 was developed at the temperature of 95 ℃ ,and the phase characterization,reservoir water adaptability,natural core physical simulation oil displacement was carried out,and residual oil start-up mode displaced by microscopic lithography model were evaluated. Further, the heterogeneous core test was carried out to evaluate the displacement effect of the system at different size slug combination. The results showed that the prepared surfactant S-2 had good solubilization ability which can form microemulsion system in low mass fraction 0.1%—0.3% with crude oil in situ,the emulsion particle size were mainly distributed in range of 65—118 nm,forming an aggregate with vesicles,and it had ultra-low interfacial tension,good adsorption resistance and temperature resistance,and the oil washing efficiency was 78%. Considering the strong fluidity of the microemulsion,the optimized temperature resistant polymer had high mobility control capability under the water quality conditions of 0.2—0.4 mg/L oxygen content and 15—20 mg/L sulfur content,the viscosity retention rate achieved more than 100% after aging for 60 days at the temperature of 95 ℃. 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 mobilized,which indicated that the system had the ability to form emulsification flooding in the whole process of displacement. The heterogeneous core test showed that the in-situ emulsion flooding system could increase the recovery rate by more than 25.2 percentage point through its variable concentration step injection combined with profile control slug injection. Considering the economic benefits and oil displacement effect,the combination injection mode of 0.1 PV profile control slug + 0.45 PV in-situ emulsification system + 0.05 PV profile control slug was selected. At present,the technology had entered the stage of pre-slug injection in the mine field,0.09 PV had been injected,the injection pressure increased by 5.0 MPa and the digital-analog predicted enhanced recovery rate was 8.06 percentage points.
-
CHEN Hao, HOU Baofeng, WANG Song, QIN Huina, XU Wei, FAN Haiming, ZHANG Fumin
2024,41(4):695-701, DOI: 10.19346/j.cnki.1000-4092.2024.04.017
Abstract:
In order to improve the temperature and salt resistance of gas reservoir water intrusion inhibitors and mitigate secondary water intrusion contamination of gas reservoirs,methanol was used as dispersion medium. Through the measurement of surface tension,contact angle,spontaneous imbibition water saturation of cores,and gas-phase permeability in porous media,the surface activity,hydrophobic modification effects,and the ability to prevent and remove water invasion damage of five surfactants were studied. By measuring infrared spectrum,contact angle,Zeta potential and adsorption layer thickness,the mechanism by which the optimal gas reservoir water invasion inhibitor altered the wettability of gas reservoir water-wet sandstone surfaces was analyzed. The results showed that,among the five surfactants,the cationic fluorine-containing bicontinuous surfactant (HB-1) had strong hydrophobic modification ability as well as good high-temperature and high-salt resistance. After aging for 24 h at 180 ℃ and a salinity of 2.0×105 mg/L,the surface tension of formation water could be lowered to 21.0 mN/m at a HB-1 concentration of 0.05%. After the core was treated with HB-1,the contact angle of formation water on the core surface increased from 45.0° before treatment to 110.0°. Injecting HB-1 into the porous medium could effectively prevent water invasion into the core,which could reduce the water saturation of core from 77.4% before treatment to 8.1%. It could effectively relieve the damage of water invasion, and then restore the gas-phase permeability of porous medium from 29.9×10-3 μm2 after water contamination to 52.3×10-3 μm2. The mechanism of HB-1 on the hydrophobic modification of water-wet sandstone surface was“adsorption”. HB-1 molecules could form a monolayer adsorption hydrophobic film with a thickness about 4.3 nm on the surface of water-wet quartz sheet. Furthermore,the thickness of adsorption film increased with increasing dosage of HB-1. When the mass fraction of HB-1 reached 0.1% ,the hydrophobic interaction between adsorption layers gradually formed a tightly oriented bilayer structure,and then the adsorption saturated. At this time,the Zeta potential was stable at 24.30 mV,and the thickness of adsorbed film was finally maintained at 4.3 nm.
-
XU Guorui, GUO Yonghua, WANG Xiaolong, CHANG Zhen, LI Xiang, FENG Xuan
2024,41(4):702-707, DOI: 10.19346/j.cnki.1000-4092.2024.04.018
Abstract:
Wellbore integrity management is one of the key issues to ensure the safe production of oil and gas wells. At present, there is a lack of independent research and development of effective plugging agent materials for offshore oilfield operations. The development of liquid high-strength plugging agent was carried out through the optimization of the main agent and curing agent system. The curing mechanism of the plugging agent was studied by means of scanning electron microscopy and infrared spectroscopy,and the simulated plugging performance was evaluated through the settlement and curing experiments. Th results showed that the developed agent had a low initial viscosity of 90 mPa·s and a high sealing compressive strength,and has good settlement and curing properties,which resulting from the strong cross-linking reaction. it was confirmed that the plugging agent had excellent pressure bearing capacity(>160 MPa/m)and could settle and cure at a height of 20 m,which has a strong plugging ability. The system had been applied to a horizontal well in A oilfield in the east of the South China Sea,and the leak point plugging operation had been successfully completed. This study provides a new pure liquid plugging agent for well integrity management, and the product has good application potential.
-
Treatment of Oily Sludge by Collaborative Processing Biosurfactant and Sediment Microbial Fuel Cells
2024,41(4):708-713, DOI: 10.19346/j.cnki.1000-4092.2024.04.019
Abstract:
A large amount of oily sludge is produced in the process of refining,storage,transportation and use of petroleum, which causes serious petroleum waste and environmental pollution. In order to solve the problem,a collaborative process of biosurfactant-sediment microbial fuel cells(SMFC) was proposed. SMFC was constructed using oily sludge pretreated with biosurfactant as the sediment. The effects of three factors,such as biosurfactant,electrogenic microorganism delivery time and oil recovery,on the electrical production and degradation performance of SMFC were investigated through detecting the daily voltage, total output electricity,power density,apparent internal resistance and oil removal rate. The results showed that the effect of biosurfactant and SMFC combined treatment of oily sludge was better than that of biosurfactant or SMFC. After the oily sludge was pretreated with biological surfactant,the addition of electric-producing microorganisms was more conducive to the degradation of oily sludge and the performance of SMFC. Compared with the treatment that electric-producing microorganisms was added before the pretreatment with biosurfactant,the total output electricity was increased by 1463.63 C and the oil removal rate was increased by 17.09 percentage point. The oil-bearing sludge SMFC constructed after recovering the oil with the biosurfactant agent had better electrical production and degradation performance,the maximum output voltage could reach up to 185.27 mV,and the oil removal rate was as high as 63.65% . The biosurfactant-SMFC could obviously improve the degradation and electricity production performance of the oily sludge,and the electric-producing microorganisms should not be put in early,and the oil recovery could greatly improve the electricity production performance of SMFC and the degradation rate of oily sludge.
-
TU Dong, ZHOU Xiaodong, YUAN Chengdong, DING Lei, AL-MUNTASERAmeenA, ZHAO Zhongwen, WUWenming, VARFOLOMEEV Mikhail A
2024,41(4):714-717, DOI: 10.19346/j.cnki.1000-4092.2024.04.020
Abstract:
The composition of Tahe ultra-heavy oil was analyzed by low field nuclear magnetic resonance(LF-NMR). Based on the composition of Tahe ultra-heavy oil,four oil-soluble viscosity reducers based on aliphatic,aromatic,aromatic + aliphatic,polar compounds were developed;and their viscosity-reducing effect was comprehensively evaluated by LF-NMR,viscosity analysis, and immersion dilution. The analysis results of crude oil group components(SARA)verified the accuracy of LF-NMR technology in analyzing crude oil composition. Except the polar compound viscosity reducer,other viscosity reducers could reduce the viscosity of ultra-heavy oil by more than 90%. The viscosity reducing performance was ranked by aromatic > mixture of aliphatic and aromatic > aliphatic > polar compound. Aromatic viscosity reducer had the best viscosity reducing effect and could reduce the viscosity from 61 000 000 mPa·s(50 ℃)to 14 897 mPa·s. At the same time,it could dissolve asphaltene and prevented asphaltenes from agglomerating. The experimental results proved that LF-NMR could not only be used as a fast and convenient method to analyze the composition of crude oils,but also be used to evaluate the effect of viscosity reducers,as well as to analyze the mechanism of viscosity reduction.
-
YANG Guojun, JIANG Yi, SHI Dongpo, WANG Yuan, SUN Jianxiao, ZHU Shenghua, TIAN Minglei, LI Geng
2024,41(4):718-724, DOI: 10.19346/j.cnki.1000-4092.2024.04.021
Abstract:
Octylphenol polyoxyethylene ether (OP-20) and sodium dodecyl sulfate (SDS) are commonly used surfactants in the later stage of oilfield exploitation. In order to accurately detect the content of each component in OP-20/SDS binary complex system, hydroxypropyl-β-cyclodextrin (HP-β-CD) was used as a masking agent to modify the UV spectroscopy and then detect the content of OP-20 in binary complex system by using its special structure of external hydrophilicity and internal hydrophobicity, as well as the characteristics of spontaneous inclusion of aromatic surfactants. At the same time, the conductivity method was used to quantitatively analyze the SDS in binary complex system, and then the effect of OP-20 on the test results was studied. The results showed that SDS could interfere with the absorbance and critical micelle concentration(ccmc)of OP-20 when the content of OP-20 in binary complex system was detected by UV spectroscopy. When 0.4 mmol/L SDS was added to 0.2 mmol/L OP-20 aqueous solution, the absorbance of OP-20 at the maximum absorption wavelength of 224 nm increased from 1.727 to 1.751. In 0.4 mmol/L SDS aqueous solution, the ccmcof OP-20 decreased from 0.223 mmol/L in pure water to 0.198 mmol/L. HP-β-CD had a significant masking effect on the detection of OP-20 in binary complex system by UV spectroscopy. HP-β-CD and OP-20 were encapsulated at a molar ratio of 1∶1, which blocked the mutual interference between OP-20 molecules and SDS molecules. After adding HP-β-CD, the recovery rate of OP-20 in binary complex system changed from 96.42%—106.92% to 99.28%—101.38% . As a result, the accuracy of detecting OP-20 content in complex system by UV spectroscopy was significantly improved. The reason why HP-β-CD eliminated the mutual interference between SDS and OP-20 was that OP-20 molecules entered the HP-β-CD molecular cavity from both wide and narrow aperture directions and then formed an inclusion complex. The conductivity method could accurately detect the content of SDS in binary complex system, while OP-20 would not interfere with SDS. When the concentration of OP-20 in the solution was 0.1—0.3 mmol/L, the recovery rate of SDS in binary complex system was 100.83%—101.92%. HP-β-CD modified UV spectroscopy combined with conductivity method could effectively detect the content of each component in OP-20/SDS binary surfactant system.
-
XIA Xiujian, YU Yongjin, QI Fengzhong, LI Changkun, XU Pu, LIU Huiting
2024,41(4):725-737, DOI: 10.19346/j.cnki.1000-4092.2024.04.022
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 discussed 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 had significant effects on improving the mechanical properties of set cement. However,their application was limited due to the dispersion difficulty of nanomaterials. Polymer latex,nanoemulsion and other organic nanoparticles could 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 was extensively studied in terms of improving the temperature resistance and comprehensive performance of polymer cementing additives. Its comprehensive performance was greatly improved compared to that of traditional polymers. In view of the major technical difficulties in complex deep and unconventional oil and gas well cementing,the research and development suggestions of polymer nano-composite cementing admixture were put forward from the two aspects,such as nano-surface grafting modification and nano-intercalation composite technology,which played an important guiding role in the research and development of key cementing additives with ultra-high temperature resistance and high performance.
-
XING Liang, DONG Zhengliang, ZHANG Yanjun, ZHANG Yanru
2024,41(4):738-748, DOI: 10.19346/j.cnki.1000-4092.2024.04.023
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 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 flowback after fracturing,thereby affecting the subsequent production of oil and gas wells. In addition,the different working fluid systems also face 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 needed to meet and current results in various stages such as fracturing,shut-in and flowback were elaborated. The characteristics and research status for polymer,surfactant,foam and gas working fluids were emphatically described. By summarizing the characteristics of working fluids mentioned above,the discussion and outlook on integrated working fluids were conducted around three aspects, such as synergistic effect of fracturing and extraction,improvement of liquid energy efficiency through temporary plugging of fracturing,and low-carbon and green transformation. The integrated working fluid involved a broad range of researches and techniques. It was necessary to strengthen the collaborative studies between multiple processes. The research results could provide a reference for the development and enhancement of integrated working fluids during fracturing,shut-in and flowback.
-
ZHENG Lintao, WANG Ruifang, ZHOU Ming, ZHANG Tianci
2024,41(4):749-757, DOI: 10.19346/j.cnki.1000-4092.2024.04.024
Abstract:
The process of oil extraction,transportation,and paper making generates a large amount of oily wastewater,which brings a great threat to the living environment of human beings. Traditional oil-water separation methods 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 extreme hydrophobicity. By combing the superhydrophobic materials used for oil-water separation in recent years,firstly,the wettability and construction methods of superhydrophobic materials were briefly introduced, and then the research progress of two-dimensional and three-dimensional superhydrophobic materials for oil-water separation was reviewed. Among them, two-dimensional superhydrophobic oil-water separation materials included fiber membranes, metal mesh, ceramics and glass, while three-dimensional superhydrophobic oil-water separation materials included rock wool,wood,aerogel,foam and sponge. Finally, some limitations of the current superhydrophobic oil-water separation materials were pointed out. Then the outlook of superhydrophobic oil-water separation materials in terms of sustainability and environmental friendliness was given,such as improving the mechanical strength of superhydrophobic surfaces, investigating the separation effect and applicability of multicomponent mixtures, combining multiple separation technologies, developing good recycling performance and multifunctionality,etc.,which provided some references and inspirations for the research of superhydrophobic materials in the field of oil-water separation.
-
LIN Zhangbi, YANG Mingjiao, WU Jianxun, ZHANG Xi
2024,41(4):756-760, DOI: 10.19346/j.cnki.1000-4092.2024.04.025
Abstract:
Oilfield Chemistry was founded in 1984. In those 40 years of trials and hardships,Oilfield Chemistry always put the quality of journal in the first place,and insisted on reporting the latest research progress,technological breakthroughs and application cases with high standards,which provided important scientific and technical support for the sustainable development of oil and gas industry. On the occasion of the 40th anniversary of Oilfield Chemistry,this editorial summarized the measures and effects taken to improve the quality and influence of the journal in recent years from the aspects of editing and publishing,digital construction,external communication and publicity,journal influence and awards. Starting at the age of 40,Oilfield Chemistry will keep in mind its original intention,base itself on the new era,keep improving the journal quality,and make greater contribution to the academic prosperity and scientific and technological innovation of oil and gas industry.
Volume 41,2024 Issue 4
-
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.
-
Construction and performance of high stability supercritical CO2 Foam for channeling blocking during CO2 flooding
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.
-
Recent progress in synthesis of oligomeric cationic surfactants
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.
-
Research status and prospect of lost circulation formation drilling fluid plugging materials
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.
-
Low interfacial tension small molecule oil displacement agent to improve oil recovery in low permeability reservoir
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
-
Performance Evaluation of Gel Plugging System for High Pressure Water Injection Well
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.
-
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.
-
Mechanical strength of polyacrylamide composite hydrogel reinforced by nanocrystalline cellulose
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.
-
Construction and Performance Evaluation of Emulsification-Stripping Dual Effect System for Heavy Oil
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.
-
Screening and evaluation of cheap nutrient system for sandstone reservoir in well block LQ, Xinjiang
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.
-
Research progress of drag reducers for fracturing and its drag reduction mechanism
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.
-
Effect of autogenous heat system on fracturing fluid gel breaking performance
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.
-
Development and application of double-protection weighting agent for drill-in fluidZhuo Lvyan You Zhiliang Zhao Cheng
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).
-
Optimization of synthesis conditions and evaluation of indoor oil displacement effect of a supercritical carbon dioxide thickener
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.
-
Experimental on lubricating oil for drilling fluid based on aging oil
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.
-
PREPARATION OF HIGHLY POROUS NI-MO CATALYST BASED ON γ-AL2O3 AND ITS CATALYTIC EFFECT ON ULTRA-HEAVY OIL VISCOSITY REDUCTION
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.
-
Evaluation of inhibition effect of ionic liquid on asphaltene precipitation in crude oil under high temperature and pressure
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.
-
Oil contaminated soil treatment new technology-the applicability of the plant type microbial fuel cell research
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.
-
Study on low temperature degradation of HPAM gel by activation of persulfate
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.
-
Study on improving anti-pollution performance of shale gas well cementing cement slurry with surfactant
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.
-
Corrosion mechanism and performance evaluation of inorganic blockages by neutral chelating system
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.
-
Viscosity Prediction Model for Water-in-Oil Emulsion Based on Quantitative Characterization of Crude Oil Physical Properties
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%.
-
Development and field application of anti-returning and plugging agents
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.
-
The corrosion inhibition performance and mechanism analysis of phenyl and benzoyl thiourea in hydrochloric acid
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.
-
Development and Function Mechanism of High Temperature Resistance Intercalation Adsorption Inhibitor
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.
-
Laboratory study on solid-free constant rheological drilling fluid with reservoir protection for deep-water drilling
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%).
-
Synthesis and Performance Evaluation of an Amphoteric Polymer Viscosity Reducer
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.
-
Effects of CO2 on the Aggregation Behaviorof Asphaltene Molecules in Heavy Oil
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.
-
Research progress and prospects of lubricants in water-based drilling fluid
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.
-
Laboratory Screening and Evaluation of Surfactant Flooding System with Salt Resistance
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.
-
Synthesis and performance study of the high temperature-resistant acid gelling agents
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
-
The effects of wettability on water coning in bottom water reservoirs
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.
-
Development and application of micro-expansion degradable gel temporary plugging agent for acid fracturing
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.
-
Synthesis, Characterization and Drag Reduction Properties of a Long-chain End-group Hydrophobically Associative Polymer
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.
-
Analysis of Factors Affecting Silicon Removal by Hydroelectric Flocculation Depth in Ultra-heavy Oil Production
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.
-
Synthesis and demulsification performance evaluation of nano iron sol stabilized by biosurfactant
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.
-
Measurement of relative permeability curve of heavy oil - water by nuclear magnetic resonance
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.
-
Preparation and Performance Evaluation of Depressurization and Oil-displacing Agent in Low Permeability Reservoir
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.
-
Plugging Mechanism and Prevention of Oil Well in Polymer Flooding Reservoir
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%.
-
The Effect and Mechanism of Surfactants with Different Interfacial Properties to Improve Oil Recovery
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.
-
Accelerating the dissolution of hydrophobically associative polymers by Cyclodextrin
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.
-
Performance evaluation and application of the microbial huff and puff system for Sheng li oil field Luo 9 Shi 1 block
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.
-
Development and Evaluation of cryogenic Microbial Demulsification System in shale oil production fracturing fluid
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.
-
Static Adsorption of JCP-1 Nano-spheres on Mineral Surface in Liquid Phase
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".
-
Cationic Surfactant Pretreats Formation to Enhance Squeeze Life of Scale Inhibitor
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.
-
Integrated Thickener with High-Viscosity and High-Drag Reduction used for Fracturing Deeper Shale Gas
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).
-
Performance evaluation of low density elastic sealing cement slurry to improve the sealing capacity between cement layers
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.
-
Research on the Mineralized Deposition of Nanoparticles and Its Application Exploration on the Improvement of Wellbore Stability
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.
-
Dynamic analysis and preparation of drag reduction and sand-carrying dual-functional polymer materials for shale fracturing
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.
-
Application of the Nanoparticles Augmented Enhanced Oil Recovery
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.
-
Development and performance evaluation of high temperature-resistant core-shell nano plugging agent used for oil-based drilling fluid
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.
-
Research on Polyelectrolyte Hydrophobic Associated Composite Suspension Stabilizer for Cementing
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.
-
Research Progress of Active Components in Crude Oil and Interaction on Influence of Emulsion Stability
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.
-
Preparation and properties of gel dispersion for profile-controlling and flooding by aqueous RAFT polymerization
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.
-
Preparation and performance evaluation of polymer microsphere as drilling fluid filtrate additive
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.
-
Preparation and analysis of acrylate- methacrylic acid copolymer emulsion reversed demulsifier
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.
-
Experimental investigation of zeolitic imidazolate framework nanoparticles for enhanced oil recovery
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.
-
Anti-blocking system in water injection process of low permeability loose sandstone reservoir with high clay
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.
-
Evaluation and application of polymer microsphere / surfactant composite profile control and flooding system
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.
-
Synthesis and Properties of a MultipStudy on Synthesis and properties of reinforced materials for oil well cement
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.
-
Foam Properties and CO2/N2 Response Properties of Anionic Surfactant/ Tertiary Amine Compound Foam
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.
-
Research progress and application prospects of drilling fluid additives in intelligent water-based drilling fluid chemical system
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.
-
The Research and Oilfield Trial of Horizontal Well Selective Water Shutoff Agent in Glutenite Oil Reservoir
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.
-
Application of New Low-damage and High-performance Micro-foam Drilling Fluid in Coalbed Methane Wells in Eastern Yunnan
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.
-
Study on the low-damage slick water fracturing fluid of Baikouquan Formation in Mahu 1# well area
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.
-
Study and Field Application of Organic Boron/Zirconium Composite Linear Gel Fracturing FluidWAN Qingshan1*, BAI Lei1,LI Bin2,CHEN Liyan1,ZHAKE Jian1
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.
-
Research on Mechanism of Pickering Microemulsion Control Swelling of Clay in Heavy Oil Reservoir
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.
-
water-soluble resin-based cementing fluid system
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.
-
Demulsification Mechanism of quartz sand on heavy oil emulsion
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.
-
Synthesis and evaluation of a new small molecular clay stabilizer ZWS-1with high temperature resistant
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.
-
Research on Imbibition of Surfactant to Improve the Production Characteristics of Crude Oil in Matrix-fracture Dual Media
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.
-
Efficient preparation of nano starch particles and its effect on the performance of drilling fluid
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.
-
Construction and properties of compound carbon quantum dotdepressurization and injection system
CHEN Gege, YU Hongjiang, LEI Liang, LIU Wenzhi
Abstract:
Objective In order to solve the problem of high water injection pressure in low permeability reservoir, taking advantage of the small size and large specific surface area of carbon quantum dots, the compound carbon quantum dots were studied. Methods Polysulfonic acid surfactant APS and amphiphilic carbon quantum dots ACQDs were used to construct a compound injection system. The interfacial tension measurement, capillary imbibition height measurement, contact Angle measurement, static oil washing and core displacement experiments are used to evaluate the pressure reduction and injection system. Results The results show that the APS/ACQDs composite pressure reducing injection system with a mass concentration of 1000 mg/L can reduce the interfacial tension of oil and water to 3.861×10-2 mN/m, the capillary imbibition height can reach 24 mm, the core contact Angle can be reduced to 52°, and the static oil washing efficiency is 77.89%. Conclusion The core displacement experiment shows that after 1PV injection of the composite system, the maximum pressure reduction rate is 23.81%, which is significantly higher than that of the single system, achieving the purpose of reducing the water injection pressure, and providing a new reference for the development of low permeability reservoir pressure reduction and injection technology.
-
Research on high activation temperature shape memory foam sealing material and sealing performance
Liu Zhendong, Li Ke, Sun Tengfei, Liu Lianying, Lv Jianren
Abstract:
Conventional leak sealing materials are often difficult to balance the structural characteristics of deformability and high pressure, resulting in poor particle size matching and pressure sealing effects. Although existing shape memory sealing materials can deform at activation temperature and achieve adaptive sealing of cracks, they have problems such as low activation temperature and insufficient compressive strength, making it difficult to cope with harsh temperature and pressure environments in deep geological conditions. This study selected epoxy resin monomers and developed foam resin materials with high activation temperature and good shape memory performance through the optimization of curing agents. The pressure sealing performance and wall strengthening effect were systematically evaluated. The evaluation results indicate that the prepared shape memory foam sealing material has a glass transition temperature of 97 ℃ and has a good sealing effect on natural crack leakage. The use of high activation temperature shape memory foam material to prepare leak stopping fluid can be applied to the sealing of fractured leak stopping wellbore walls, which has great significance in broadening the safety density window, reducing accidents and complexity.
-
Research on the synthesis and application of polyurethane plugging agent
MU Meng, LI Yang, LI Xingyao, SHU Qinglin, LIU Heng, ZHANG Yongmin, TANG Xutao
Abstract:
Plugging agent plays a key role in the process of oil development, quality improvement and efficiency enhancement. However, there are some problems such as insufficient plugging strength, short validity period and low water plugging efficiency. Therefore, the research on high-strength plugging system has become areas of research focus. In this paper, a kind of organic cross-linked gel plugging agent was developed. With polyhydroxyethylacrylamide (PHEAA) as the skeleton molecule, 1,6-hexane diisocyanate ( HDI ) as the crosslinking agent, N, N-dimethylformamide ( DMF ) and dimethyl sulfoxide(DMSO)mixed solution as the solvent, an organic plugging system ( ADI ) that can undergo sol-gel phase transition under constant temperature conditions was successfully constructed. The influence of polymer, ( HDI ) content and temperature on the gelation time and gel strength were systematically investigated. The results demonstrate that the strength of the gelled organic gel is proportional to the concentration of the polymer and the concentration of the crosslinking agent, and the gelation time is adversely proportional to the temperature. While the content of PHEAA and HDI increased from 10%, 2% to 16%, 5 %, respectively, the corresponding elastic modulus increased from 991 to 3100Pa, and the viscosity increased from 22400 to 45100 mPa.s, separately. Accompanied with the ambient temperature increased from 45 °C to 125 °C, the gelation time decreased from 3h to 13min. The solid-state transition of the system is mainly attributed to the nucleophilic reaction between HDI and hydroxyl groups in PHEAA. The artificial core plugging experiment confirmed that when the volume of liquid plugging system injected to the core reached to 1 PV, the plugging strength after solidifing could reach up to 26.11 MPa, illustrating the potential application for water plugging and profile control.
-
Study on the effect of modified ZrO2 nanoparticles combined with low-salinity water for oil displacement
He Long, Wang Xuening, Xue Peng, Wang Xuenfeng
Abstract:
Nanoparticle flooding and low-salinity waterflooding are widely studied by researchers as new and popular enhanced recovery technologies. To further investigate the synergistic effect of ZrO2 nanoparticles and low-salinity water, the low-salinity water is now obtained by diluting the formation water of the Taha oil field by 110 times to obtain 5% additional recovery and is used as the optimal low-salinity water. In order to improve the dispersion of ZrO2 nanoparticles in low-salinity water, a modified ZrO2 nanoparticles by the coupling agent 3-aminopropyltrimethoxysilane was prepared. Infrared spectroscopy, transmission electron microscopy and thermogravimetric analyzer were used to analyze and characterize the particles. Dispersion stability, interfacial properties and oil displacement effect of nanofluids combined with FW-110 times low- salinity water and modified ZrO2 nanoparticles were evaluated. The dispersibility of the modified nanofluid was improved from 22.9 to 7.6; the interfacial tension was further reduced by 2 mN/m; the wettability of the rock surface was further shifted to water-wetness; the work of adhesion was further reduced by 8 J/cm2; and the increase in temperature had a positive effect on the reduction of the interfacial tension, contact angle, and work of adhesion. The optimum concentration of particles was 0.02 wt% at 0.005 wt%~0.05 wt%, when the highest indoor recovery rate was achieved, with a value-added recovery rate of 12.6%, which provided a theoretical basis with obvious advantages and broad prospects for popularization and application.
-
Performance of Water-Alternating-Gas Assisted CO2 Flooding in Conglomerate Reservoirs.
XU Chongjun, LIU Jiaxing, HUI Zeyou, LI Zhihong, LUO Qiang, PU Wanfen
Abstract:
Oilfield are rich in remaining oil, positioning CO2 flooding as a promising enhanced oil recovery (EOR) technique. However, the inherent reservoir heterogeneity, coupled with the differing mobilities of oil and gas, poses a substantial risk of gas channeling during CO2 injection. Water-alternating-gas (WAG) injection, a widely recognized method for mitigating gas channeling, requires further investigation to assess its effectiveness in this region. This study employs natural conglomerate cores with varying permeabilities to evaluate the impact of WAG on the performance and oil recovery of CO2 flooding under heterogeneous conditions. The results indicate that WAG significantly reduces intra-layer gas channeling, but the aqueous phase dampens the interaction between CO2 and crude oil, leading to a reduction in low-carbon components in the produced oil. Furthermore, when inter-layer and intra-layer heterogeneities coexist, the effectiveness of WAG in controlling channeling and enhancing oil recovery diminishes, highlighting the need for additional mobility control techniques, such as in-situ foam. This research offers valuable insights into the feasibility of WAG in the Bai 21 well block and provides practical guidance for optimizing gas channeling control strategies in similar heterogeneous reservoirs.
-
Emulsification Characteristics and Influencing Factors Analysis of Shale Oil and Water in the Second Member Kongdian Formation of Cangdong Sag in Dagang Oilfield
LI Qi, WANG Xiaoyan, GE Hongjiang, LI Dongping, WANG Haifeng, ZHANG Nan
Abstract:
The primary fracturing in the second member of Kongdian Formation of Cangdong Sag in Dagang Oilfield exhibits significant effects during the initial stage, but energy and output decline rapidly in later stages, and the produced fluids are severely emulsified, resulting in a reduction of shale oil recovery, increasing difficulty of shale oil development, gathering, and transportation. This study aims to investigate the emulsification characteristics of shale oil with water in-depth and identify their influencing factors, thereby revealing the reasons and mechanisms behind shale oil emulsification, and thus proposing solutions for issues related to thickening due to this phenomenon. The findings reveal that the average wax content of shale oil in the second member of the Kongdian Formation exceeds 20%, with a pour point above 35°C. Moreover, the high content of heavy hydrocarbons favors the occurrence of the emulsification phenomenon. Nitrogen-containing polar compounds (i.e. asphaltenes and resins) and wax crystals facilitate the formation of water-in-oil (W/O) emulsions under flow conditions, resulting in thickening attributed to these emulsification processes. The viscosity of shale oil increases first and then decreases with the increase in water content. It reaches a maximum when water content ranges from 50% to 70%, attaining viscosities that are 3.23 to 7.45 times higher than that of dehydrated shale oil. The stability of W/O emulsion formed through the emulsification process of shale oil and water is enhanced by increasing emulsification temperature, increasing salinity of the water phase, and intruding fracturing fluid composition. Additionally, O/W/O multiple emulsions will be formed when emulsified shale oil is re-emulsified, further increasing the viscosity of the shale oil system. However, introducing a small amount of PSG surfactants during this re-emulsifying process can reverse the configuration from W/O back into an O/W structure for the resultant emulsion, thus reducing the viscosity of shale oil and improving its fluidity. Therefore, it is necessary to consider the physical and chemical properties of shale oil when conducting water injections and energy enhancement for shale oil reservoirs. Simultaneously, the development of high-activity surfactants for shale oil stimulation will be a focal point for subsequent process design and product research and development.
-
Preparation and Performance Evaluation of Environmentally Friendly Temperature and Salt Resistant Thickener for Shale Oil Drilling
MA Haiyun, LYU Shuang, YAN Han, DING Keyu
Abstract:
In order to improve the temperature and salt resistance as well as environmental performance of water-based drilling fluid thickening agents, and meet the needs of shale oil drilling construction, an environmentally friendly temperature and salt resistant thickening agent HBZ-2 was prepared using methacrylamide (MAA), N-vinyl pyrrolidone (NVP), and polymerizable quaternary ammonium salt cationic monomer (H-12) as raw materials. The molecular structure of the thickening agent HBZ-2 was characterized indoors, its mechanism of action was analyzed, and its thickening performance, temperature and salt resistance, environmental performance, and basic performance of drilling fluid were investigated. The results showed that under the same experimental conditions, the environmentally friendly temperature and salt resistant thickening agent HBZ-2 had better thickening performance, temperature resistance, and salt resistance than the same type of thickening agents HE300 and 80A51. When the dosage of the thickening agent HBZ-2 is 1%, after high-temperature aging at 200 ℃, the viscosity of the seawater slurry can still reach over 30mPa · s after adding 20% sodium chloride or 5% calcium chloride, indicating strong temperature and salt resistance. The basic performance of the drilling fluid system with the addition of viscosity enhancer HBZ-2 after high-temperature aging is relatively stable. In addition, the viscosity enhancer HBZ-2 has low biological toxicity, good biodegradability, and does not contain heavy metals, with excellent environmental performance. The research results indicate that the environmentally friendly temperature and salt resistant thickening agent HBZ-2 has excellent performance and is suitable for application in offshore shale oil drilling wells with high environmental performance requirements.
-
Fabrication and Performance Evaluation of Filter Loss Reducer with Double Cross-linked Architectures
Abstract:
It is difficult to meet the needs of drilling engineering by simply changing the type and proportion of copolymer functional groups, for artificially synthesized polymers to be used as filtrate reducers for water-based drilling fluids, increasing the usage of energetic monomers will undoubtedly increase its cost, especially under ultra-high temperature and high salinity conditions, This study prepared a dual cross-linked fluid loss reducer by adding salt resistant monomer 2-acrylamide-2-methylpropanesulfonic acid (AMPS) and temperature resistant monomer N-vinylpyrrolidone (NVP) to the main monomer acrylamide (AM), and using organic and metal crosslinkers. Using the high-temperature filtration reduction effect of polymers as the evaluation index, single factor experiments were used to optimize the synthesis conditions: stirring speed of 300 rpm, monomer mass ratio AM/AMPS/NVP of 18/1/1, crosslinking agent dosage of 2.0wt%, organic crosslinking agent/metal crosslinking agent mass ratio (OC/MC) of 1/3, oil-water mass ratio of 3/2, and initiator dosage of 1.0 wt%. And the particle size distribution, surface morphology, element distribution, microstructure, and heat resistance of the copolymer were characterized using laser particle size analyzer, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM-EDS), and thermogravimetric analyzer (TGA). The high temperature and high pressure filtration loss (FLHTHP) and API filtration loss (FLAPI) of the system containing 1.0wt/vol% polymer decreased from 77.6mL and 18.8mL respectively to 31.2ml and 6.6ml after 16 hours of hot rolling at 210 ℃. The results indicate that the addition of a dual cross-linked structure filtrate reducer can significantly improve the high-temperature resistance of the base slurry. This article elaborates on the high-temperature and salt resistance mechanism of a dual cross-linked structure fluid loss reducer. The hydrolyzed polymer molecular chain undergoes secondary cross-linking with the metal cross-linking agent, which protects the hydrolyzed polymer molecular chain from rapid degradation and forms a more dense and complex three-dimensional network structure, resulting in excellent temperature resistance and fluid loss performance of the polymer fluid loss reducer.
-
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.
-
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.
-
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
-
WANG Zhihua1,2,XU Yunfei1,QI Xiangdong1,LIU Xiaoyu1,HONG Jiajun1
2021,38(2):360-367, DOI: 10.19346/j.cnki.1000-4092.2021.02.028
Abstract:
The stability of emulsions presents a significant challenge in surface process particularly,both in terms of crude oil dehydration and produced water treatment. Considering the potential influence of asphaltene and resin in crude oil,especially the polymer and surfactant would be appeared in actual produced emulsions in chemical flooding process. This paper reviewed the application and research progress of molecular dynamics simulation in the field of oil- water interface stability mechanism. The available methods and relevant software for characterizing the visualization,density distribution,radial distribution function,oil water interface formation energy,and molecular diffusion coefficient were discussed,respectively. In order to understand the interphase interaction of crude oil emulsions and address it,the molecular dynamics simulation could be used as an effective method according to the existed research. The review indicated that breaking through the limitations of model simplification and single factor simulation to understand the molecular adsorption,droplet coalescence,and droplet separation from micro-scale was a research application and development direction of molecular dynamics simulation in the fields of oil- water emulsification and demulsification. Furthermore,the component properties of internal phase and external phase,and the temperature and pressure conditions need to be considered.
-
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.
-
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.
-
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.
-
SHU Zhan,PEI Haihua,ZHANG Guicai,GE Jijiang,JIANG Ping,CAO Xu
2020,37(1):185-190, DOI: 10.19346/j.cnki.1000-4092.2020.01.032
Abstract:
Steam-assisted gravity drainage(SAGD)technology is widely used in the production of ultra-heavy oil,but there are problems such as severe steam channeling and low heat utilization during the development process. By summarizing the current main technical methods to improve the development effect of SAGD,such as gas-assisted SAGD technology,solvent-assisted SAGD technology,foam-assisted SAGD technology and chemical additive-assisted SAGD technology,the mechanism of improving SAGD technology and the effect of improving recovery efficiency were introduced. The existing problems and suggestions for use were put forward. The differences between reservoir geological conditions and construction conditions should be considered comprehensively,and different auxiliary SAGD technologies should be selected to maximize the economic benefits.
-
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.
-
ZHOU Linbi,QIN Bing,LI Wei,WANG Zheng
2020,37(3):557-563, DOI: 10.19346/j.cnki.1000-4092.2020.03.032
Abstract:
Viscosity reduction and mobility improvement are very crucial in heavy oil recovery. The mechanism,development and application of main viscosity reduction methods at home and abroad were discussed and compared,including thermal treatment based on steam injection,fire flooding,emusification,catalytic reaction,solvent dilution and microbial viscosity reduction. The characteristics and disadvantages of these methods were summarized. Finally,the development directions of heavy oil viscosity reduction technology were proposed.
-
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.
-
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.
-
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.
-
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.
-
YAO Lan1,LI Huanxiang1,JIAO Wei2,ZHOU Jiang2,KE Congyu3,ZHANG Qunzheng3
2022,39(3):548-553, DOI: 10.19346/j.cnki.1000-4092.2022.03.028
Abstract:
With the increasing expansion of the development scale of oil and gas fields,the contradiction between the gradual increase of water consumption for fracturing operation and the large amount of fracturing flowback fluid that cannot be directly discharged is further highlighted. It is undoubtedly an effective way to solve this problem that treat the flowback liquid and reuse it. Aiming at the reuse research and application status of fracturing flowback fluid in China,this paper systematically introduced the technical problems faced in the process of flowback fluid treatment,the research and development of recyclable fracturing fluid system,the improvement of flowback fluid treatment process and treatment device. Treating and reusing the flowback liquid was the best way and was also the inevitable trend of future development of oil and gas field industry. The development of flowback fluid reuse technology should start from the research and development of recyclable fracturing fluid system and the improvement of flowback fluid reuse treatment process,so as to further improve and popularize the application of this technology in the process of oil and gas field development. In view of the problems existing in the current reuse technology of flowback liquid,some suggestions were put forward in order to provide guidance for the development of reuse technology of flowback liquid in China.
-
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.
-
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.
-
ZHAO Hongbo1,2,3,SHAN Wenjun2,3,ZHU Disi2,3,YUE Weimin2,3,HE Yuanxin1,2,3
2021,38(4):740-746, DOI: 10.19346/j.cnki.1000-4092.2021.04.028
Abstract:
The latest achievements in the aspects of lost circulation mechanism,types of lost circulation materials,drilling fluid formulation and technology was reviewed. In addition,the engineering methods of well prevention,such as well strengthening, and the advantages and disadvantages of the methods for determining the leakage layer was also introduced. Finally,some suggestions was given,which can be used for reference in the future.
-
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.