Enhanced oil recovery(EOR)refers to themanymethodologies used to augment the volume of crude oil extracted froman oil reservoir.These approaches are used subsequent to the exhaustion of basic and secondary recovery me...Enhanced oil recovery(EOR)refers to themanymethodologies used to augment the volume of crude oil extracted froman oil reservoir.These approaches are used subsequent to the exhaustion of basic and secondary recovery methods.There are three primary categories of Enhanced Oil Recovery(EOR):thermal,gas injection,and chemical.Enhanced oil recovery methods may be costly and intricate;yet,they facilitate the extraction of supplementary oil that would otherwise remain in the reservoir.Enhanced Oil Recovery(EOR)may prolong the lifespan of an oil field and augment the total output from a specific field.The parameters influencing oil recovery are a significant problem in Enhanced Oil Recovery(EOR)systems,necessitating further examination of the components that impact them.This research examined the impact of permeability fluctuations on fluid dynamics inside a sandstone reservoir and presented a contemporary overview of the three phases of Enhanced Oil Recovery(EOR),including detailed explanations of the methodologies used and the processes facilitating oil recovery.The challenges faced with several common EOR mechanisms were identified,and solutions were suggested.Additionally,the modern trend of incorporating nanotechnology and its synergistic impacts on the stability and efficacy of conventional chemicals for enhanced oil recovery(EOR)was scrutinised and evaluated.Ultimately,laboratory results and field activities were examined.The study looked closely at hownanoparticlesmove through reservoirs and evaluated enhanced oil recovery(EOR),mobility ratio,and fluid displacement efficiency.This study offers comprehensive insights into the use of enhanced oil recovery techniques for sustainable energy generation.展开更多
In deep oil reservoir development,enhanced oil recovery(EOR)techniques encounter significant challenges under high-temperature and high-salinity conditions.Traditional profile-control agents often fail to maintain sta...In deep oil reservoir development,enhanced oil recovery(EOR)techniques encounter significant challenges under high-temperature and high-salinity conditions.Traditional profile-control agents often fail to maintain stable blocking under extreme conditions and exhibit poor resistance to high temperature and high salinity.This study develops a functionalized nanographite system(the MEGO system)with superior high-temperature dispersibility and thermosalinity-responsive capability through polyether amine(PEA)grafting and noncovalent interactions with disodium naphthalene sulfonate(DNS)molecules.The grafted PEA and DNS provide steric hindrance and electrostatic repulsion,enhancing thermal and salinity resistance.After ten days of aggregation,the MEGO system forms stable particle aggregates(55.51-61.80 lm)that are suitable for deep reservoir migration and profile control.Both experiments and simulations reveal that particle size variations are synergistically controlled by temperature and salt ions(Na^(+),Ca^(2+),and Mg^(2+)).Compared with monovalent ions,divalent ions promote nanographite aggregation more strongly through double-layer compression and bridging effects.In core displacement experiments,the MEGO system demonstrated superior performance in reservoirs with permeabilities ranging from 21.6 to 103 mD.The aggregates formed within the pore throats significantly enhanced flow resistance,expanded the sweep volume,and increased the overall oil recovery to 56.01%.This research indicates that the MEGO system holds excellent potential for EOR in deep oil reservoirs.展开更多
During oil displacement,surfactants often encounter challenges such as emulsion instability and channeling,which can compromise their efficiency.To address these issues,polymer microspheres were synthesized via revers...During oil displacement,surfactants often encounter challenges such as emulsion instability and channeling,which can compromise their efficiency.To address these issues,polymer microspheres were synthesized via reverse microemulsion polymerization using acrylamide,2-methyl-2-acrylamidopropane sulfonic acid,and stearyl methacrylate as monomers,with N,N-methylenebisacrylamide as the crosslinker.The microspheres were then combined with sodium alkyl alcohol polyoxyethylene ether carboxylate to enhance emulsion stability and expand the swept volume of surfactant.A stable reverse microemulsion system was prepared using the maximum water solubilization rate as the indicator,and microspheres were synthesized based on this system.The ability of the microspheres to enhance emulsion stability was systematically evaluated.The plugging performance and enhanced oil recovery(EOR)efficiency of the microsphere/surfactant composite system were assessed through core seepage and oil displacement experiments.The experimental results demonstrated that microspheres were successfully prepared in a water-in-oil reverse microemulsion system with a solubilization rate of 42%.The emulsion stability was evaluated under an oil-to-water ratio of 7:3,a temperature of 80℃,and a salinity of 44,592 mg/L,by manually shaking the test tube five times.It was observed that the complete phase separation time of the emulsion increased from 10 to 120 min after the addition of microspheres.Under different permeability conditions(100×10^(-3),300×10^(-3),500×10^(-3)μm^(2)),the recovery efficiency of the composite system increased by 4.5%,8.3%,and 4.8%,respectively,compared to a single surfactant system.The microspheres developed in this study enhanced emulsion stability and increased the swept volume of surfactant within the formation,significantly boosting its oil recovery efficiency.展开更多
High-water-cut mature reservoirs typically serve as the“ballast”for ensuring China’s annual crude oil production of 200 million tons.Despite the use of water flooding and chemical methods,over 40%of crude oil remai...High-water-cut mature reservoirs typically serve as the“ballast”for ensuring China’s annual crude oil production of 200 million tons.Despite the use of water flooding and chemical methods,over 40%of crude oil remains unexploited.It is critical to develop efficient revolutionary technologies to further enhance oil recovery(EOR)by a large percentage in high-water-cut mature reservoirs.To address this issue,the potential of vertical remaining oil in Daqing Oilfield is first analyzed from massive monitoring data.Using molecular dynamics simulation to design optimal synthetic routine,a copolymer without flu-orine or silicon is synthesized by modifying vinyl acetate(VAc)with maleic anhydride(MA)and styrene(St),and treated as a supercritical CO_(2)(scCO_(2))thickener.The underlying EOR mechanism of the scCO_(2) thickener is thereafter clarified by high-temperature,high-pressure oil displacement experiments.The EOR effect by thickened scCO_(2) flooding in a typical high-water-cut mature reservoir is predicted,and future technological advancements of the technique are ultimately discussed.Results show that the ver-tical remaining oil enriched in weakly swept zones is a primary target for further EOR in high-water-cut mature reservoirs.The copolymer typically exhibits good solubility,strong dispersion stability,and high thickening effect in scCO_(2).Under an ambient pressure of 10 MPa and a temperature of 50℃,the disso-lution of copolymer at a mass concentration of 0.2%can effectively increase the viscosity of scCO_(2) by 39.4 times.Due to the synergistic effect between expanding vertical swept volume and inhibiting gas channel-ing,crude oil recovery can be further enhanced by 23.1%for a typical high-water-cut mature reservoir when the scCO_(2) viscosity is increased by 50 times.Our understandings demonstrate that the thickened scCO_(2) flooding technology has significant technical advantages in high-water-cut mature reservoirs,with challenges and future development directions in field-scale applications also highlighted.展开更多
This paper introduces a novel approach combining radial borehole fracturing with Water-Alternating-Gas(WAG)injection,enabling simultaneous WAG injection and shale oil production in a single vertical well.A numerical r...This paper introduces a novel approach combining radial borehole fracturing with Water-Alternating-Gas(WAG)injection,enabling simultaneous WAG injection and shale oil production in a single vertical well.A numerical reservoir model incorporating the modified exponential non-Darcy law,stress sensitivity,and diffusion is established.The spatial distribution of permeability reduction shows that stress sensitivity enhances the non-Darcy effect,with apparent permeability decreasing to 0-92.1%of the initial value,highlighting the importance of maintaining reservoir pressure.Continuous CO_(2) flooding leads to early gas breakthrough,while continuous water flooding has less displacement efficiency.A 30%water-to-gas injection time ratio improves oil production and delays gas breakthrough compared to continuous CO_(2) injection.Optimal conditions for effective recovery are identified as an initial production period of 100 d and a well vertical spacing of 30 m.This study compares the production capacity of WAG operations under radial borehole fracturing and horizontal well fracturing.When the number of wells is two for both cases,the production capacity of radial borehole fracturing is comparable to that of five-stage horizontal well fracturing,indicating that radial borehole fracturing can serve as an alternative or supplement to horizontal well fracturing when the reservoir volume is limited.This study offers a new method and theoretical basis for the efficient development of shale oil.展开更多
Carbon dioxide Enhanced Oil Recovery(CO_(2)-EOR)technology guarantees substantial underground CO_(2) sequestration while simultaneously boosting the production capacity of subsurface hydrocarbons(oil and gas).However,...Carbon dioxide Enhanced Oil Recovery(CO_(2)-EOR)technology guarantees substantial underground CO_(2) sequestration while simultaneously boosting the production capacity of subsurface hydrocarbons(oil and gas).However,unreasonable CO_(2)-EOR strategies,encompassing well placement and well control parameters,will lead to premature gas channeling in production wells,resulting in large amounts of CO_(2) escape without any beneficial effect.Due to the lack of prediction and optimization tools that integrate complex geological and engineering information for the widely used CO_(2)-EOR technology in promising industries,it is imperative to conduct thorough process simulations and optimization evaluations of CO_(2)-EOR technology.In this paper,a novel optimization workflow that couples the AST-GraphTrans-based proxy model(Attention-based Spatio-temporal Graph Transformer)and multi-objective optimization algorithm MOPSO(Multi-objective Particle Swarm Optimization)is established to optimize CO_(2)-EOR strategies.The workflow consists of two outstanding components.The AST-GraphTrans-based proxy model is utilized to forecast the dynamics of CO_(2) flooding and sequestration,which includes cumulative oil production,CO_(2) sequestration volume,and CO_(2) plume front.And the MOPSO algorithm is employed for achieving maximum oil production and maximum sequestration volume by coordinating well placement and well control parameters with the containment of gas channeling.By the collaborative coordination of the two aforementioned components,the AST-GraphTrans proxy-assisted optimization workflow overcomes the limitations of rapid optimization in CO_(2)-EOR technology,which cannot consider high-dimensional spatio-temporal information.The effectiveness of the proposed workflow is validated on a 2D synthetic model and a 3D field-scale reservoir model.The proposed workflow yields optimizations that lead to a significant increase in cumulative oil production by 87%and 49%,and CO_(2) sequestration volume enhancement by 78%and 50%across various reservoirs.These findings underscore the superior stability and generalization capabilities of the AST-GraphTrans proxy-assisted framework.The contribution of this study is to provide a more efficient prediction and optimization tool that maximizes CO_(2) sequestration and oil recovery while mitigating CO_(2) gas channeling,thereby ensuring cleaner oil production.展开更多
This paper reviews the basic research means for oilfield development and also the researches and tests of enhanced oil recovery(EOR)methods for mature oilfields and continental shale oil development,analyzes the probl...This paper reviews the basic research means for oilfield development and also the researches and tests of enhanced oil recovery(EOR)methods for mature oilfields and continental shale oil development,analyzes the problems of EOR methods,and proposes the relevant research prospects.The basic research means for oilfield development include in-situ acquisition of formation rock/fluid samples and non-destructive testing.The EOR methods for conventional and shale oil development are classified as improved water flooding(e.g.nano-water flooding),chemical flooding(e.g.low-concentration middle-phase micro-emulsion flooding),gas flooding(e.g.micro/nano bubble flooding),thermal recovery(e.g.air injection thermal-aided miscible flooding),and multi-cluster uniform fracturing/water-free fracturing,which are discussed in this paper for their mechanisms,approaches,and key technique researches and field tests.These methods have been studied with remarkable progress,and some achieved ideal results in field tests.Nonetheless,some problems still exist,such as inadequate research on mechanisms,imperfect matching technologies,and incomplete industrial chains.It is proposed to further strengthen the basic researches and expand the field tests,thereby driving the formation,promotion and application of new technologies.展开更多
Emulsification is one of the important mechanisms of surfactant flooding. To improve oil recovery for low permeability reservoirs, a highly efficient emulsification oil flooding system consisting of anionic surfactant...Emulsification is one of the important mechanisms of surfactant flooding. To improve oil recovery for low permeability reservoirs, a highly efficient emulsification oil flooding system consisting of anionic surfactant sodium alkyl glucosyl hydroxypropyl sulfonate(APGSHS) and zwitterionic surfactant octadecyl betaine(BS-18) is proposed. The performance of APGSHS/BS-18 mixed surfactant system was evaluated in terms of interfacial tension, emulsification capability, emulsion size and distribution, wettability alteration, temperature-resistance and salt-resistance. The emulsification speed was used to evaluate the emulsification ability of surfactant systems, and the results show that mixed surfactant systems can completely emulsify the crude oil into emulsions droplets even under low energy conditions. Meanwhile,the system exhibits good temperature and salt resistance. Finally, the best oil recovery of 25.45% is achieved for low permeability core by the mixed surfactant system with a total concentration of 0.3 wt%while the molar ratio of APGSHS:BS-18 is 4:6. The current study indicates that the anionic/zwitterionic mixed surfactant system can improve the oil flooding efficiency and is potential candidate for application in low permeability reservoirs.展开更多
The intensive development of tight reservoirs has positioned them as a strategic alternative to conventional oil and gas resources. Existing enhanced oil recovery(EOR) methods struggle to effectively exploring reservo...The intensive development of tight reservoirs has positioned them as a strategic alternative to conventional oil and gas resources. Existing enhanced oil recovery(EOR) methods struggle to effectively exploring reservoir oil, resulting in low recovery rates. Novel and effective means of developing tight reservoirs are urgently needed. Nanomaterials have shown promising applications in improving water flooding efficiency, with in-depth research into mechanisms that lower injection pressure and increase water injection volumes. However, the extent of improvement remains limited. In this study, a silicon quantum dots(Si-QDs) material was synthesized via a hydrothermal synthesis method and used to prepare a nanofluid for the efficient recovery of tight reservoir. The Si-QDs, with an approximate diameter of 3 nm and a spherical structure, were surface functionalized with benzenesulfonic acid groups to enhance the performance. The developed nanofluid demonstrated stability without aggregation at 120℃ and a salinity of 60000 mg/L. Core flooding experiments have demonstrated the attractive EOR capabilities of Si-QDs, shedding light of the EOR mechanisms. Si-QDs effectively improve the wettability of rocks, enhancing the sweeping coefficient of injected fluids and expanding sweeping area.Within this sweeping region, Si-QDs efficiently stripping adsorbed oil from the matrix, thus increasing sweeping efficiency. Furthermore, Si-QDs could modify the state of pore-confined crude oil, breaking it down into smaller particles that are easier to displacement in subsequent stages. Si-QDs exhibit compelling EOR potential, positioning them as a promising approach for effectively developing tight oil reservoirs.展开更多
This study introduces a novel method integrating CO_(2)flooding with radial borehole fracturing for enhanced oil recovery and CO_(2)underground storage,a solution to the limited vertical stimulation reservoir volume i...This study introduces a novel method integrating CO_(2)flooding with radial borehole fracturing for enhanced oil recovery and CO_(2)underground storage,a solution to the limited vertical stimulation reservoir volume in horizontal well fracturing.A numerical model is established to investigate the production rate,reservoir pressure field,and CO_(2)saturation distribution corresponding to changing time of CO_(2)flooding with radial borehole fracturing.A sensitivity analysis on the influence of CO_(2)injection location,layer spacing,pressure difference,borehole number,and hydraulic fractures on oil production and CO_(2)storage is conducted.The CO_(2)flooding process is divided into four stages.Reductions in layer spacing will significantly improve oil production rate and gas storage capacity.However,serious gas channeling can occur when the spacing is lower than 20 m.Increasing the pressure difference between the producer and injector,the borehole number,the hydraulic fracture height,and the fracture width can also increase the oil production rate and gas storage rate.Sensitivity analysis shows that layer spacing and fracture height greatly influence gas storage and oil production.Research outcomes are expected to provide a theoretical basis for the efficient development of shale oil reservoirs in the vertical direction.展开更多
Laboratory experiments,numerical simulations and fracturing technology were combined to address the problems in shale oil recovery by CO_(2)injection.The laboratory experiments were conducted to investigate the displa...Laboratory experiments,numerical simulations and fracturing technology were combined to address the problems in shale oil recovery by CO_(2)injection.The laboratory experiments were conducted to investigate the displacement mechanisms of shale oil extraction by CO_(2)injection,and the influences of CO_(2)pre-pad on shale mechanical properties.Numerical simulations were performed about influences of CO_(2)pre-pad fracturing and puff-n-huff for energy replenishment on the recovery efficiency.The findings obtained were applied to the field tests of CO_(2)pre-pad fracturing and single well puff-n-huff.The results show that the efficiency of CO_(2)puff-n-huff is affected by micro-and nano-scale effect,kerogen,adsorbed oil and so on,and a longer soaking time in a reasonable range leads to a higher exploitation degree of shale oil.In the"injection+soaking"stage,the exploitation degree of heavy hydrocarbons is enhanced by CO_(2)through its effects of solubility-diffusion and mass-transfer.In the"huff"stage,crude oil in large pores is displaced by CO_(2)to surrounding larger pores or bedding fractures and finally flows to the production well.The injection of CO_(2)pre-pad is conducive to keeping the rock brittle and reducing the fracture breakdown pressure,and the CO_(2)is liable to filter along the bedding surface,thereby creating a more complex fracture.Increasing the volume of CO_(2)pre-pad can improve the energizing effect,and enhance the replenishment of formation energy.Moreover,the oil recovery is more enhanced by CO_(2)huff-n-puff with the lower shale matrix permeability,the lower formation pressure,and the larger heavy hydrocarbon content.The field tests demonstrate a good performance with the pressure maintained well after CO_(2)pre-pad fracturing,the formation energy replenished effectively after CO_(2)huff-n-puff in a single well,and the well productivity improved.展开更多
Polymerflooding is an effective method widely applied for enhancing oil recovery(EOR)by reducing the mobility ratio between theinjected water and crude oil.However,traditional polymers encounter challenges in high sali...Polymerflooding is an effective method widely applied for enhancing oil recovery(EOR)by reducing the mobility ratio between theinjected water and crude oil.However,traditional polymers encounter challenges in high salinity reservoirs due to their salt sensitivity.Toovercome this challenge,we synthesized a zwitterion polymer(PAMNS)with salt-induced tackifying property through copolymerization ofacrylamide and a zwitterion monomer,methylacrylamide propyl-N,N-dimethylbutylsulfonate(NS).NS monomer is obtained from thereaction between 1,4-butanesultone and dimethylamino propyl methylacrylamide.In this study,the rheological properties,salt responsiveness,and EOR efficiency of PAMNS were evaluated.Results demonstrate that PAMNS exhibits desirable salt-induced tackifyingcharacteristics,with viscosity increasing up to 2.4 times as the NaCl concentration reaches a salinity of 30×10^(4)mg L^(-1).Furthermore,highvalence ions possess a much stronger effect on enhancing viscosity,manifested as Mg^(2+)>Ca^(2+)>Na^(+).Molecular dynamics simulations(MD)andfluid dynamics experiment results demonstrate that PAMNS molecules exhibit a more stretched state and enhanced intermolecularassociations in high-salinity environments.It is because of the salt-induced tackifying,PAMNS demonstrates superior performance inpolymerflooding experiments under salinity ranges from 5×10^(4)mg L^(-1)to 20×10^(4)mg L^(-1),leading to 10.38–19.83%higher EOR thantraditional polymers.展开更多
CO_(2) emulsions used for EOR have received a lot of interest because of its good performance on CO_(2)mobility reduction.However,most of them have been focusing on the high quality CO_(2) emulsion(high CO_(2) fractio...CO_(2) emulsions used for EOR have received a lot of interest because of its good performance on CO_(2)mobility reduction.However,most of them have been focusing on the high quality CO_(2) emulsion(high CO_(2) fraction),while CO_(2) emulsion with high water cut has been rarely researched.In this paper,we carried out a comprehensive experimental study of using high water cut CO_(2)/H_(2)O emulsion for enhancing oil recovery.Firstly,a nonionic surfactant,alkyl glycosides(APG),was selected to stabilize CO_(2)/H_(2)O emulsion,and the corresponding morphology and stability were evaluated with a transparent PVT cell.Subsequently,plugging capacity and apparent viscosity of CO_(2)/H_(2)O emulsion were measured systematically by a sand pack displacement apparatus connected with a 1.95-m long capillary tube.Furthermore,a high water cut(40 vol%) CO_(2)/H_(2)O emulsion was selected for flooding experiments in a long sand pack and a core sample,and the oil recovery,the rate of oil recovery,and the pressure gradients were analyzed.The results indicated that APG had a good performance on emulsifying and stabilizing CO_(2) emulsion.An inversion from H_(2)O/CO_(2) emulsion to CO_(2)/H_(2)O emulsion with the increase in water cut was confirmed.CO_(2)/H_(2)O emulsions with lower water cuts presented higher apparent viscosity,while the optimal plugging capacity of CO_(2)/H_(2)O emulsion occurred at a certain water cut.Eventually,the displacement using CO_(2)/H_(2)O emulsion provided 18.98% and 13.36% additional oil recovery than that using pure CO_(2) in long sand pack and core tests,respectively.This work may provide guidelines for EOR using CO_(2) emulsions with high water cut.展开更多
Carbonated water injection(CWI)is a promising enhanced oil recovery(EOR)technology that has received much attention in co-optimizing CO_(2) storage and oil recovery.This study provides a comprehensive review of the fl...Carbonated water injection(CWI)is a promising enhanced oil recovery(EOR)technology that has received much attention in co-optimizing CO_(2) storage and oil recovery.This study provides a comprehensive review of the fluid system properties and the underlying changes in rock-fluid interactions that drive the CWI-EOR mechanisms.Previous research has indicated that CWI can enhance oil recovery by shifting reservoir wettability towards a more water-wet state and reducing interfacial tension(IFT).However,this study reveals that there is still room for discussion in this area.Notably,the potential of CWI to alter reservoir permeability has not yet been explored.The varying operational conditions of the CWI process,namely temperature,pressure,injection rate,salinity,and ionic composition,lead to different levels of oil recovery factors.Herein,we aim to meticulously analyze their impact on oil recovery performance and outline the optimal operational conditions.Pressure,for instance,positively influences oil recovery rate and CWI efficiency.On one hand,higher operating pressures enhance the effectiveness of CW due to increased CO_(2)solubility.On the other hand,gas exsolution events in depleted reservoirs provide additional energy for oil movement along gas growth pathways.However,CWI at high carbonation levels does not offer significant benefits over lower carbonation levels.Additionally,lower temperatures and injection rates correlate with higher recovery rates.Further optimization of solution chemistry is necessary to determine the maximum recovery rates under optimal conditions.Moreover,this review comprehensively covers laboratory experiments,numerical simulations,and field applications involving the CWI process.However,challenges such as pipeline corrosion,potential reservoir damage,and produced water treatment impact the further application of CWI in EOR technologies.These issues can affect the expected oil recovery rates,thereby reducing the economic returns of EOR projects.Finally,this review introduces current research trends and future development prospects based on recently published studies in the field of CWI.The conclusions of this study aid readers in better understanding the latest advancements in CWI technology and the strengths and limitations of the techniques used,providing directions for further development and application of CWI.展开更多
This paper describes a simple, easy process for screening microorganisms, and introduces a laboratory simulation device and process of microbial enhanced oil recovery (MEOR) , which is a necessary research step for t...This paper describes a simple, easy process for screening microorganisms, and introduces a laboratory simulation device and process of microbial enhanced oil recovery (MEOR) , which is a necessary research step for trial in oilfields. The MEOR mechanism and the influence of adsorption, diffusion, metabolism, nutrition, porosity, and permeability are analyzed. The research indicates that different microbes have different efficiencies in EOR and that different culture types play different roles in EOR. The effect of syrup is better than that of glucose, and larger porosity is favorable to the reproduction and growth of microbes, thereby improving the oil recovery. Using crude oil as a single carbon source is more appreciable because of the decrease in cost of oil recovery. At the end of this paper, the development of polymerase chain reaction (PCR) for the future is discussed.展开更多
This paper describes the experience of Jilin oilfield trials for Microbial Enhanced Oil Recovery (MEOR). A new technique to identify microbes with DNA for MEOR has been established, and useful microbes selected f...This paper describes the experience of Jilin oilfield trials for Microbial Enhanced Oil Recovery (MEOR). A new technique to identify microbes with DNA for MEOR has been established, and useful microbes selected for use in field trials. Behaviors of bacteria activated in the reservoir, oil recovery and water cut, and the viscosity of crude oil produced through huff & puff testing and flooding with molasses-injection tests, have been investigated in situ. CJF-002, which produces biopolysaccharide, is the best among the microbes used for field trials, as it can use molasses as nutrient and produce a small quantity of CO2 and a mass of water-insoluble biopolymer. The metabolic behavior in the reservoir showed that CJF-002 had a good potentiality for MEOR.展开更多
India is currently producing crude oil from matured fields because of insufficient discoveries of new fields.Therefore,in order to control the energy crisis in India,enhanced oil recovery(EOR)techniques are required t...India is currently producing crude oil from matured fields because of insufficient discoveries of new fields.Therefore,in order to control the energy crisis in India,enhanced oil recovery(EOR)techniques are required to reduce the import of crude from the OPEC(Organization of the Petroleum Exporting Countries).This review mentions chemical EOR techniques(polymers,surfactants,alkali,nanoparticles,and combined alkali-surfactant-polymer flooding)and operations in India.Chemical EOR methods are one of the most efficient methods for oil displacement.The efficiency is enhanced by interfacial tension(IFT)reduction using surfactants and alkali,and mobility control of injected water is done by adding a polymer to increase the volumetric sweep efficiency.This paper also reviews the current trend of chemical EOR,prospects of chemical EOR in Indian oilfields,the development of chemical EOR in India with their challenges raising with economics,and screening criteria for chemical EOR implementation on the field scale.Furthermore,the review gives a brief idea about chemical EOR implementation in Indian oilfields in future prospects to increase the additional oil recovery from existing depleted fields to reduce the import of crude oil.The outcome of this review depicts all chemical EOR operations and recovery rates both at the laboratory scale and field scale around the country.The additional recovery rates are compared from various chemical EOR methods like conventional chemical flooding methods and conventional chemicals combined with nanoparticles on a laboratory scale.The development of chemical EOR in the past few decades and the EOR policy given by the government of India has been mentioned in this review.The analysis provides an idea about enhanced recovery screening and implementation of chemical EOR methods in existing fields will significantly reduce the energy crisis in India.展开更多
Low permeability oil and gas resources are rich and have great potential all over the world, which has gradually become the main goal of oil and gas development. However, after traditional primary and secondary exploi...Low permeability oil and gas resources are rich and have great potential all over the world, which has gradually become the main goal of oil and gas development. However, after traditional primary and secondary exploitation, there is still a large amount of remaining oil that has not been recovered.Therefore, in recent years, enhanced oil recovery(EOR) technologies for low permeability reservoirs have been greatly developed to further improve crude oil production. This study presents a comprehensive review of EOR technologies in low permeability reservoirs with an emphasis on gas flooding, surfactant flooding, nanofluid flooding and imbibition EOR technologies. In addition, two kinds of gel systems are introduced for conformance control in low permeability reservoirs with channeling problems. Finally,the technical challenges, directions and outlooks of EOR in low permeability reservoirs are addressed.展开更多
Reservoir wettability plays an important role in various oil recovery processes.The origin and evolution of reservoir wettability were critically reviewed to better understand the complexity of wettability due to inte...Reservoir wettability plays an important role in various oil recovery processes.The origin and evolution of reservoir wettability were critically reviewed to better understand the complexity of wettability due to interactions in crude oil-brine-rock system,with introduction of different wetting states and their influence on fluid distribution in pore spaces.The effect of wettability on oil recovery of waterflooding was then summarized from past and recent research to emphasize the importance of wettability in oil displacement by brine.The mechanism of wettability alteration by different surfactants in both carbonate and sandstone reservoirs was analyzed,concerning their distinct surface chemistry,and different interaction patterns of surfactants with components on rock surface.Other concerns such as the combined effect of wettability alteration and interfacial tension （IFT） reduction on the imbibition process was also taken into account.Generally,surfactant induced wettability alteration for enhanced oil recovery is still in the stage of laboratory investigation.The successful application of this technique relies on a comprehensive survey of target reservoir conditions,and could be expected especially in low permeability fractured reservoirs and forced imbibition process.展开更多
A significant fraction of the conventional oil reserves globally is in carbonate formations which contain a substantial amount of residual oil. Since primary and secondary recovery methods fail to yield above 20%-40%o...A significant fraction of the conventional oil reserves globally is in carbonate formations which contain a substantial amount of residual oil. Since primary and secondary recovery methods fail to yield above 20%-40%of original oil in place from these reserves, the need for enhanced oil recovery（EOR） techniques for incremental oil recovery has become imperative. With the challenges presented by the highly heterogeneous carbonate rocks,evaluation of tertiary-stage recovery techniques including chemical EOR（c EOR） has been a high priority for researchers and oil producers. In this review, the latest developments in the surfactant-based c EOR techniques applied in carbonate formations are discussed, contemplating the future direction of existing methodologies. In connection with this, the characteristics of heterogeneous carbonate reservoirs are outlined. Detailed discussion on surfactant-led oil recovery mechanisms and related processes, such as wettability alteration, interfacial tension reduction, microemulsion phase behavior, surfactant adsorption and mitigation, and foams and their applications is presented. Laboratory experiments, as well as field study data obtained using several surfactants, are also included.This extensive discussion on the subject aims to help researchers and professionals in the field to understand the current situation and plan future enterprises accordingly.展开更多
文摘Enhanced oil recovery(EOR)refers to themanymethodologies used to augment the volume of crude oil extracted froman oil reservoir.These approaches are used subsequent to the exhaustion of basic and secondary recovery methods.There are three primary categories of Enhanced Oil Recovery(EOR):thermal,gas injection,and chemical.Enhanced oil recovery methods may be costly and intricate;yet,they facilitate the extraction of supplementary oil that would otherwise remain in the reservoir.Enhanced Oil Recovery(EOR)may prolong the lifespan of an oil field and augment the total output from a specific field.The parameters influencing oil recovery are a significant problem in Enhanced Oil Recovery(EOR)systems,necessitating further examination of the components that impact them.This research examined the impact of permeability fluctuations on fluid dynamics inside a sandstone reservoir and presented a contemporary overview of the three phases of Enhanced Oil Recovery(EOR),including detailed explanations of the methodologies used and the processes facilitating oil recovery.The challenges faced with several common EOR mechanisms were identified,and solutions were suggested.Additionally,the modern trend of incorporating nanotechnology and its synergistic impacts on the stability and efficacy of conventional chemicals for enhanced oil recovery(EOR)was scrutinised and evaluated.Ultimately,laboratory results and field activities were examined.The study looked closely at hownanoparticlesmove through reservoirs and evaluated enhanced oil recovery(EOR),mobility ratio,and fluid displacement efficiency.This study offers comprehensive insights into the use of enhanced oil recovery techniques for sustainable energy generation.
基金supported by the General Program of the National Natural Science Foundation of China(52074335)the National Key Research and Development Program of China(2022YFE0129900 and 2019YFA0708700)+1 种基金the Fundamental Research Funds for the Central Universities(23CX07003A)the Special Funding Program for the Operational Expenses of National Research Institutions(SKLDOG2024-ZYRC-01).
文摘In deep oil reservoir development,enhanced oil recovery(EOR)techniques encounter significant challenges under high-temperature and high-salinity conditions.Traditional profile-control agents often fail to maintain stable blocking under extreme conditions and exhibit poor resistance to high temperature and high salinity.This study develops a functionalized nanographite system(the MEGO system)with superior high-temperature dispersibility and thermosalinity-responsive capability through polyether amine(PEA)grafting and noncovalent interactions with disodium naphthalene sulfonate(DNS)molecules.The grafted PEA and DNS provide steric hindrance and electrostatic repulsion,enhancing thermal and salinity resistance.After ten days of aggregation,the MEGO system forms stable particle aggregates(55.51-61.80 lm)that are suitable for deep reservoir migration and profile control.Both experiments and simulations reveal that particle size variations are synergistically controlled by temperature and salt ions(Na^(+),Ca^(2+),and Mg^(2+)).Compared with monovalent ions,divalent ions promote nanographite aggregation more strongly through double-layer compression and bridging effects.In core displacement experiments,the MEGO system demonstrated superior performance in reservoirs with permeabilities ranging from 21.6 to 103 mD.The aggregates formed within the pore throats significantly enhanced flow resistance,expanded the sweep volume,and increased the overall oil recovery to 56.01%.This research indicates that the MEGO system holds excellent potential for EOR in deep oil reservoirs.
基金supported by the Natural Science Foundation of Shandong Province(ZR2021ME007)the National Natural Science Foundation in China(51574267)the Key Projects of China National Key Research and Development Plan(2019YFA0708703)。
文摘During oil displacement,surfactants often encounter challenges such as emulsion instability and channeling,which can compromise their efficiency.To address these issues,polymer microspheres were synthesized via reverse microemulsion polymerization using acrylamide,2-methyl-2-acrylamidopropane sulfonic acid,and stearyl methacrylate as monomers,with N,N-methylenebisacrylamide as the crosslinker.The microspheres were then combined with sodium alkyl alcohol polyoxyethylene ether carboxylate to enhance emulsion stability and expand the swept volume of surfactant.A stable reverse microemulsion system was prepared using the maximum water solubilization rate as the indicator,and microspheres were synthesized based on this system.The ability of the microspheres to enhance emulsion stability was systematically evaluated.The plugging performance and enhanced oil recovery(EOR)efficiency of the microsphere/surfactant composite system were assessed through core seepage and oil displacement experiments.The experimental results demonstrated that microspheres were successfully prepared in a water-in-oil reverse microemulsion system with a solubilization rate of 42%.The emulsion stability was evaluated under an oil-to-water ratio of 7:3,a temperature of 80℃,and a salinity of 44,592 mg/L,by manually shaking the test tube five times.It was observed that the complete phase separation time of the emulsion increased from 10 to 120 min after the addition of microspheres.Under different permeability conditions(100×10^(-3),300×10^(-3),500×10^(-3)μm^(2)),the recovery efficiency of the composite system increased by 4.5%,8.3%,and 4.8%,respectively,compared to a single surfactant system.The microspheres developed in this study enhanced emulsion stability and increased the swept volume of surfactant within the formation,significantly boosting its oil recovery efficiency.
基金the National Natural Science Foundation of China(U22B6005,52174043,52474035)the Beijing Natural Science Foundation(3242019)the China National Petroleum Corporation(CNPC)Innovation Foundation(2022DQ02-0208 and 2024DQ02-0114).
文摘High-water-cut mature reservoirs typically serve as the“ballast”for ensuring China’s annual crude oil production of 200 million tons.Despite the use of water flooding and chemical methods,over 40%of crude oil remains unexploited.It is critical to develop efficient revolutionary technologies to further enhance oil recovery(EOR)by a large percentage in high-water-cut mature reservoirs.To address this issue,the potential of vertical remaining oil in Daqing Oilfield is first analyzed from massive monitoring data.Using molecular dynamics simulation to design optimal synthetic routine,a copolymer without flu-orine or silicon is synthesized by modifying vinyl acetate(VAc)with maleic anhydride(MA)and styrene(St),and treated as a supercritical CO_(2)(scCO_(2))thickener.The underlying EOR mechanism of the scCO_(2) thickener is thereafter clarified by high-temperature,high-pressure oil displacement experiments.The EOR effect by thickened scCO_(2) flooding in a typical high-water-cut mature reservoir is predicted,and future technological advancements of the technique are ultimately discussed.Results show that the ver-tical remaining oil enriched in weakly swept zones is a primary target for further EOR in high-water-cut mature reservoirs.The copolymer typically exhibits good solubility,strong dispersion stability,and high thickening effect in scCO_(2).Under an ambient pressure of 10 MPa and a temperature of 50℃,the disso-lution of copolymer at a mass concentration of 0.2%can effectively increase the viscosity of scCO_(2) by 39.4 times.Due to the synergistic effect between expanding vertical swept volume and inhibiting gas channel-ing,crude oil recovery can be further enhanced by 23.1%for a typical high-water-cut mature reservoir when the scCO_(2) viscosity is increased by 50 times.Our understandings demonstrate that the thickened scCO_(2) flooding technology has significant technical advantages in high-water-cut mature reservoirs,with challenges and future development directions in field-scale applications also highlighted.
基金the Young Scientists Fund of the National Natural Science Foundation of China(52204063)the Key Laboratory of Shale Gas Exploration,Ministry of Natural Resources(Chongqing Institute of Geology and Mineral Resources),Chongqing,China(KLSGE-202202).
文摘This paper introduces a novel approach combining radial borehole fracturing with Water-Alternating-Gas(WAG)injection,enabling simultaneous WAG injection and shale oil production in a single vertical well.A numerical reservoir model incorporating the modified exponential non-Darcy law,stress sensitivity,and diffusion is established.The spatial distribution of permeability reduction shows that stress sensitivity enhances the non-Darcy effect,with apparent permeability decreasing to 0-92.1%of the initial value,highlighting the importance of maintaining reservoir pressure.Continuous CO_(2) flooding leads to early gas breakthrough,while continuous water flooding has less displacement efficiency.A 30%water-to-gas injection time ratio improves oil production and delays gas breakthrough compared to continuous CO_(2) injection.Optimal conditions for effective recovery are identified as an initial production period of 100 d and a well vertical spacing of 30 m.This study compares the production capacity of WAG operations under radial borehole fracturing and horizontal well fracturing.When the number of wells is two for both cases,the production capacity of radial borehole fracturing is comparable to that of five-stage horizontal well fracturing,indicating that radial borehole fracturing can serve as an alternative or supplement to horizontal well fracturing when the reservoir volume is limited.This study offers a new method and theoretical basis for the efficient development of shale oil.
基金supported by the National Natural Science Foundation of China(Nos.52374064,52274056)China Scholarship Council(No.202406450086).
文摘Carbon dioxide Enhanced Oil Recovery(CO_(2)-EOR)technology guarantees substantial underground CO_(2) sequestration while simultaneously boosting the production capacity of subsurface hydrocarbons(oil and gas).However,unreasonable CO_(2)-EOR strategies,encompassing well placement and well control parameters,will lead to premature gas channeling in production wells,resulting in large amounts of CO_(2) escape without any beneficial effect.Due to the lack of prediction and optimization tools that integrate complex geological and engineering information for the widely used CO_(2)-EOR technology in promising industries,it is imperative to conduct thorough process simulations and optimization evaluations of CO_(2)-EOR technology.In this paper,a novel optimization workflow that couples the AST-GraphTrans-based proxy model(Attention-based Spatio-temporal Graph Transformer)and multi-objective optimization algorithm MOPSO(Multi-objective Particle Swarm Optimization)is established to optimize CO_(2)-EOR strategies.The workflow consists of two outstanding components.The AST-GraphTrans-based proxy model is utilized to forecast the dynamics of CO_(2) flooding and sequestration,which includes cumulative oil production,CO_(2) sequestration volume,and CO_(2) plume front.And the MOPSO algorithm is employed for achieving maximum oil production and maximum sequestration volume by coordinating well placement and well control parameters with the containment of gas channeling.By the collaborative coordination of the two aforementioned components,the AST-GraphTrans proxy-assisted optimization workflow overcomes the limitations of rapid optimization in CO_(2)-EOR technology,which cannot consider high-dimensional spatio-temporal information.The effectiveness of the proposed workflow is validated on a 2D synthetic model and a 3D field-scale reservoir model.The proposed workflow yields optimizations that lead to a significant increase in cumulative oil production by 87%and 49%,and CO_(2) sequestration volume enhancement by 78%and 50%across various reservoirs.These findings underscore the superior stability and generalization capabilities of the AST-GraphTrans proxy-assisted framework.The contribution of this study is to provide a more efficient prediction and optimization tool that maximizes CO_(2) sequestration and oil recovery while mitigating CO_(2) gas channeling,thereby ensuring cleaner oil production.
基金Supported by the PetroChina Science and Technology Major Project(2023ZZ04,2023ZZ08)。
文摘This paper reviews the basic research means for oilfield development and also the researches and tests of enhanced oil recovery(EOR)methods for mature oilfields and continental shale oil development,analyzes the problems of EOR methods,and proposes the relevant research prospects.The basic research means for oilfield development include in-situ acquisition of formation rock/fluid samples and non-destructive testing.The EOR methods for conventional and shale oil development are classified as improved water flooding(e.g.nano-water flooding),chemical flooding(e.g.low-concentration middle-phase micro-emulsion flooding),gas flooding(e.g.micro/nano bubble flooding),thermal recovery(e.g.air injection thermal-aided miscible flooding),and multi-cluster uniform fracturing/water-free fracturing,which are discussed in this paper for their mechanisms,approaches,and key technique researches and field tests.These methods have been studied with remarkable progress,and some achieved ideal results in field tests.Nonetheless,some problems still exist,such as inadequate research on mechanisms,imperfect matching technologies,and incomplete industrial chains.It is proposed to further strengthen the basic researches and expand the field tests,thereby driving the formation,promotion and application of new technologies.
基金financially supported by National Natural Science Foundation of China(No.22302229)Beijing Municipal Excellent Talent Training Funds Youth Advanced Individual Project(No.2018000020124G163)。
文摘Emulsification is one of the important mechanisms of surfactant flooding. To improve oil recovery for low permeability reservoirs, a highly efficient emulsification oil flooding system consisting of anionic surfactant sodium alkyl glucosyl hydroxypropyl sulfonate(APGSHS) and zwitterionic surfactant octadecyl betaine(BS-18) is proposed. The performance of APGSHS/BS-18 mixed surfactant system was evaluated in terms of interfacial tension, emulsification capability, emulsion size and distribution, wettability alteration, temperature-resistance and salt-resistance. The emulsification speed was used to evaluate the emulsification ability of surfactant systems, and the results show that mixed surfactant systems can completely emulsify the crude oil into emulsions droplets even under low energy conditions. Meanwhile,the system exhibits good temperature and salt resistance. Finally, the best oil recovery of 25.45% is achieved for low permeability core by the mixed surfactant system with a total concentration of 0.3 wt%while the molar ratio of APGSHS:BS-18 is 4:6. The current study indicates that the anionic/zwitterionic mixed surfactant system can improve the oil flooding efficiency and is potential candidate for application in low permeability reservoirs.
基金the financial support from the National Natural Science Foundation of China (Nos. 52074249, 51874261, 52304011)。
文摘The intensive development of tight reservoirs has positioned them as a strategic alternative to conventional oil and gas resources. Existing enhanced oil recovery(EOR) methods struggle to effectively exploring reservoir oil, resulting in low recovery rates. Novel and effective means of developing tight reservoirs are urgently needed. Nanomaterials have shown promising applications in improving water flooding efficiency, with in-depth research into mechanisms that lower injection pressure and increase water injection volumes. However, the extent of improvement remains limited. In this study, a silicon quantum dots(Si-QDs) material was synthesized via a hydrothermal synthesis method and used to prepare a nanofluid for the efficient recovery of tight reservoir. The Si-QDs, with an approximate diameter of 3 nm and a spherical structure, were surface functionalized with benzenesulfonic acid groups to enhance the performance. The developed nanofluid demonstrated stability without aggregation at 120℃ and a salinity of 60000 mg/L. Core flooding experiments have demonstrated the attractive EOR capabilities of Si-QDs, shedding light of the EOR mechanisms. Si-QDs effectively improve the wettability of rocks, enhancing the sweeping coefficient of injected fluids and expanding sweeping area.Within this sweeping region, Si-QDs efficiently stripping adsorbed oil from the matrix, thus increasing sweeping efficiency. Furthermore, Si-QDs could modify the state of pore-confined crude oil, breaking it down into smaller particles that are easier to displacement in subsequent stages. Si-QDs exhibit compelling EOR potential, positioning them as a promising approach for effectively developing tight oil reservoirs.
基金This study has been funded by the National Science Fund for Distinguished Young Scholars(No.52204063)Science Foundation of China University of Petroleum,Beijing(No.2462023BJRC025).Moreover,we would like to express our heartfelt appreciation to the Computational Geosciences group in the Department of Mathematics and Cybernetics at SINTEF Digital for developing and providing the free open-source MATLAB Reservoir Simulation Toolbox(MRST)used in this research.
文摘This study introduces a novel method integrating CO_(2)flooding with radial borehole fracturing for enhanced oil recovery and CO_(2)underground storage,a solution to the limited vertical stimulation reservoir volume in horizontal well fracturing.A numerical model is established to investigate the production rate,reservoir pressure field,and CO_(2)saturation distribution corresponding to changing time of CO_(2)flooding with radial borehole fracturing.A sensitivity analysis on the influence of CO_(2)injection location,layer spacing,pressure difference,borehole number,and hydraulic fractures on oil production and CO_(2)storage is conducted.The CO_(2)flooding process is divided into four stages.Reductions in layer spacing will significantly improve oil production rate and gas storage capacity.However,serious gas channeling can occur when the spacing is lower than 20 m.Increasing the pressure difference between the producer and injector,the borehole number,the hydraulic fracture height,and the fracture width can also increase the oil production rate and gas storage rate.Sensitivity analysis shows that layer spacing and fracture height greatly influence gas storage and oil production.Research outcomes are expected to provide a theoretical basis for the efficient development of shale oil reservoirs in the vertical direction.
基金Supported by Basic and Forward-Looking Project of the Science and Technology Department of SINOPEC(P22213-4)。
文摘Laboratory experiments,numerical simulations and fracturing technology were combined to address the problems in shale oil recovery by CO_(2)injection.The laboratory experiments were conducted to investigate the displacement mechanisms of shale oil extraction by CO_(2)injection,and the influences of CO_(2)pre-pad on shale mechanical properties.Numerical simulations were performed about influences of CO_(2)pre-pad fracturing and puff-n-huff for energy replenishment on the recovery efficiency.The findings obtained were applied to the field tests of CO_(2)pre-pad fracturing and single well puff-n-huff.The results show that the efficiency of CO_(2)puff-n-huff is affected by micro-and nano-scale effect,kerogen,adsorbed oil and so on,and a longer soaking time in a reasonable range leads to a higher exploitation degree of shale oil.In the"injection+soaking"stage,the exploitation degree of heavy hydrocarbons is enhanced by CO_(2)through its effects of solubility-diffusion and mass-transfer.In the"huff"stage,crude oil in large pores is displaced by CO_(2)to surrounding larger pores or bedding fractures and finally flows to the production well.The injection of CO_(2)pre-pad is conducive to keeping the rock brittle and reducing the fracture breakdown pressure,and the CO_(2)is liable to filter along the bedding surface,thereby creating a more complex fracture.Increasing the volume of CO_(2)pre-pad can improve the energizing effect,and enhance the replenishment of formation energy.Moreover,the oil recovery is more enhanced by CO_(2)huff-n-puff with the lower shale matrix permeability,the lower formation pressure,and the larger heavy hydrocarbon content.The field tests demonstrate a good performance with the pressure maintained well after CO_(2)pre-pad fracturing,the formation energy replenished effectively after CO_(2)huff-n-puff in a single well,and the well productivity improved.
基金support of the National Natural Science Foundation of China(No.52120105007)the National Key Research and Development Program of China(2019Y FA0708700)are gratefully acknowledged.
文摘Polymerflooding is an effective method widely applied for enhancing oil recovery(EOR)by reducing the mobility ratio between theinjected water and crude oil.However,traditional polymers encounter challenges in high salinity reservoirs due to their salt sensitivity.Toovercome this challenge,we synthesized a zwitterion polymer(PAMNS)with salt-induced tackifying property through copolymerization ofacrylamide and a zwitterion monomer,methylacrylamide propyl-N,N-dimethylbutylsulfonate(NS).NS monomer is obtained from thereaction between 1,4-butanesultone and dimethylamino propyl methylacrylamide.In this study,the rheological properties,salt responsiveness,and EOR efficiency of PAMNS were evaluated.Results demonstrate that PAMNS exhibits desirable salt-induced tackifyingcharacteristics,with viscosity increasing up to 2.4 times as the NaCl concentration reaches a salinity of 30×10^(4)mg L^(-1).Furthermore,highvalence ions possess a much stronger effect on enhancing viscosity,manifested as Mg^(2+)>Ca^(2+)>Na^(+).Molecular dynamics simulations(MD)andfluid dynamics experiment results demonstrate that PAMNS molecules exhibit a more stretched state and enhanced intermolecularassociations in high-salinity environments.It is because of the salt-induced tackifying,PAMNS demonstrates superior performance inpolymerflooding experiments under salinity ranges from 5×10^(4)mg L^(-1)to 20×10^(4)mg L^(-1),leading to 10.38–19.83%higher EOR thantraditional polymers.
基金The financial supports received from the National Natural Science Foundation of China(Nos.22178378,22127812)。
文摘CO_(2) emulsions used for EOR have received a lot of interest because of its good performance on CO_(2)mobility reduction.However,most of them have been focusing on the high quality CO_(2) emulsion(high CO_(2) fraction),while CO_(2) emulsion with high water cut has been rarely researched.In this paper,we carried out a comprehensive experimental study of using high water cut CO_(2)/H_(2)O emulsion for enhancing oil recovery.Firstly,a nonionic surfactant,alkyl glycosides(APG),was selected to stabilize CO_(2)/H_(2)O emulsion,and the corresponding morphology and stability were evaluated with a transparent PVT cell.Subsequently,plugging capacity and apparent viscosity of CO_(2)/H_(2)O emulsion were measured systematically by a sand pack displacement apparatus connected with a 1.95-m long capillary tube.Furthermore,a high water cut(40 vol%) CO_(2)/H_(2)O emulsion was selected for flooding experiments in a long sand pack and a core sample,and the oil recovery,the rate of oil recovery,and the pressure gradients were analyzed.The results indicated that APG had a good performance on emulsifying and stabilizing CO_(2) emulsion.An inversion from H_(2)O/CO_(2) emulsion to CO_(2)/H_(2)O emulsion with the increase in water cut was confirmed.CO_(2)/H_(2)O emulsions with lower water cuts presented higher apparent viscosity,while the optimal plugging capacity of CO_(2)/H_(2)O emulsion occurred at a certain water cut.Eventually,the displacement using CO_(2)/H_(2)O emulsion provided 18.98% and 13.36% additional oil recovery than that using pure CO_(2) in long sand pack and core tests,respectively.This work may provide guidelines for EOR using CO_(2) emulsions with high water cut.
基金supported by National Key Research and Development Program of China(Grant No.2023YFB4104200)Liaoning Foundation Research Projects for Application(Grant No.2023JH2/101300005)National Natural Science Foundation of China(Grant No.51976024,52076030)。
文摘Carbonated water injection(CWI)is a promising enhanced oil recovery(EOR)technology that has received much attention in co-optimizing CO_(2) storage and oil recovery.This study provides a comprehensive review of the fluid system properties and the underlying changes in rock-fluid interactions that drive the CWI-EOR mechanisms.Previous research has indicated that CWI can enhance oil recovery by shifting reservoir wettability towards a more water-wet state and reducing interfacial tension(IFT).However,this study reveals that there is still room for discussion in this area.Notably,the potential of CWI to alter reservoir permeability has not yet been explored.The varying operational conditions of the CWI process,namely temperature,pressure,injection rate,salinity,and ionic composition,lead to different levels of oil recovery factors.Herein,we aim to meticulously analyze their impact on oil recovery performance and outline the optimal operational conditions.Pressure,for instance,positively influences oil recovery rate and CWI efficiency.On one hand,higher operating pressures enhance the effectiveness of CW due to increased CO_(2)solubility.On the other hand,gas exsolution events in depleted reservoirs provide additional energy for oil movement along gas growth pathways.However,CWI at high carbonation levels does not offer significant benefits over lower carbonation levels.Additionally,lower temperatures and injection rates correlate with higher recovery rates.Further optimization of solution chemistry is necessary to determine the maximum recovery rates under optimal conditions.Moreover,this review comprehensively covers laboratory experiments,numerical simulations,and field applications involving the CWI process.However,challenges such as pipeline corrosion,potential reservoir damage,and produced water treatment impact the further application of CWI in EOR technologies.These issues can affect the expected oil recovery rates,thereby reducing the economic returns of EOR projects.Finally,this review introduces current research trends and future development prospects based on recently published studies in the field of CWI.The conclusions of this study aid readers in better understanding the latest advancements in CWI technology and the strengths and limitations of the techniques used,providing directions for further development and application of CWI.
文摘This paper describes a simple, easy process for screening microorganisms, and introduces a laboratory simulation device and process of microbial enhanced oil recovery (MEOR) , which is a necessary research step for trial in oilfields. The MEOR mechanism and the influence of adsorption, diffusion, metabolism, nutrition, porosity, and permeability are analyzed. The research indicates that different microbes have different efficiencies in EOR and that different culture types play different roles in EOR. The effect of syrup is better than that of glucose, and larger porosity is favorable to the reproduction and growth of microbes, thereby improving the oil recovery. Using crude oil as a single carbon source is more appreciable because of the decrease in cost of oil recovery. At the end of this paper, the development of polymerase chain reaction (PCR) for the future is discussed.
文摘This paper describes the experience of Jilin oilfield trials for Microbial Enhanced Oil Recovery (MEOR). A new technique to identify microbes with DNA for MEOR has been established, and useful microbes selected for use in field trials. Behaviors of bacteria activated in the reservoir, oil recovery and water cut, and the viscosity of crude oil produced through huff & puff testing and flooding with molasses-injection tests, have been investigated in situ. CJF-002, which produces biopolysaccharide, is the best among the microbes used for field trials, as it can use molasses as nutrient and produce a small quantity of CO2 and a mass of water-insoluble biopolymer. The metabolic behavior in the reservoir showed that CJF-002 had a good potentiality for MEOR.
文摘India is currently producing crude oil from matured fields because of insufficient discoveries of new fields.Therefore,in order to control the energy crisis in India,enhanced oil recovery(EOR)techniques are required to reduce the import of crude from the OPEC(Organization of the Petroleum Exporting Countries).This review mentions chemical EOR techniques(polymers,surfactants,alkali,nanoparticles,and combined alkali-surfactant-polymer flooding)and operations in India.Chemical EOR methods are one of the most efficient methods for oil displacement.The efficiency is enhanced by interfacial tension(IFT)reduction using surfactants and alkali,and mobility control of injected water is done by adding a polymer to increase the volumetric sweep efficiency.This paper also reviews the current trend of chemical EOR,prospects of chemical EOR in Indian oilfields,the development of chemical EOR in India with their challenges raising with economics,and screening criteria for chemical EOR implementation on the field scale.Furthermore,the review gives a brief idea about chemical EOR implementation in Indian oilfields in future prospects to increase the additional oil recovery from existing depleted fields to reduce the import of crude oil.The outcome of this review depicts all chemical EOR operations and recovery rates both at the laboratory scale and field scale around the country.The additional recovery rates are compared from various chemical EOR methods like conventional chemical flooding methods and conventional chemicals combined with nanoparticles on a laboratory scale.The development of chemical EOR in the past few decades and the EOR policy given by the government of India has been mentioned in this review.The analysis provides an idea about enhanced recovery screening and implementation of chemical EOR methods in existing fields will significantly reduce the energy crisis in India.
基金supported by Key Program of National Natural Science Foundation of China (No. 52130401)National Natural Science Foundation of China (No. 52104055)+1 种基金China National Postdoctoral Program for Innovative Talents (No. BX20200386)China Postdoctoral Science Foundation (No. 2021M703586)。
文摘Low permeability oil and gas resources are rich and have great potential all over the world, which has gradually become the main goal of oil and gas development. However, after traditional primary and secondary exploitation, there is still a large amount of remaining oil that has not been recovered.Therefore, in recent years, enhanced oil recovery(EOR) technologies for low permeability reservoirs have been greatly developed to further improve crude oil production. This study presents a comprehensive review of EOR technologies in low permeability reservoirs with an emphasis on gas flooding, surfactant flooding, nanofluid flooding and imbibition EOR technologies. In addition, two kinds of gel systems are introduced for conformance control in low permeability reservoirs with channeling problems. Finally,the technical challenges, directions and outlooks of EOR in low permeability reservoirs are addressed.
文摘Reservoir wettability plays an important role in various oil recovery processes.The origin and evolution of reservoir wettability were critically reviewed to better understand the complexity of wettability due to interactions in crude oil-brine-rock system,with introduction of different wetting states and their influence on fluid distribution in pore spaces.The effect of wettability on oil recovery of waterflooding was then summarized from past and recent research to emphasize the importance of wettability in oil displacement by brine.The mechanism of wettability alteration by different surfactants in both carbonate and sandstone reservoirs was analyzed,concerning their distinct surface chemistry,and different interaction patterns of surfactants with components on rock surface.Other concerns such as the combined effect of wettability alteration and interfacial tension （IFT） reduction on the imbibition process was also taken into account.Generally,surfactant induced wettability alteration for enhanced oil recovery is still in the stage of laboratory investigation.The successful application of this technique relies on a comprehensive survey of target reservoir conditions,and could be expected especially in low permeability fractured reservoirs and forced imbibition process.
文摘A significant fraction of the conventional oil reserves globally is in carbonate formations which contain a substantial amount of residual oil. Since primary and secondary recovery methods fail to yield above 20%-40%of original oil in place from these reserves, the need for enhanced oil recovery（EOR） techniques for incremental oil recovery has become imperative. With the challenges presented by the highly heterogeneous carbonate rocks,evaluation of tertiary-stage recovery techniques including chemical EOR（c EOR） has been a high priority for researchers and oil producers. In this review, the latest developments in the surfactant-based c EOR techniques applied in carbonate formations are discussed, contemplating the future direction of existing methodologies. In connection with this, the characteristics of heterogeneous carbonate reservoirs are outlined. Detailed discussion on surfactant-led oil recovery mechanisms and related processes, such as wettability alteration, interfacial tension reduction, microemulsion phase behavior, surfactant adsorption and mitigation, and foams and their applications is presented. Laboratory experiments, as well as field study data obtained using several surfactants, are also included.This extensive discussion on the subject aims to help researchers and professionals in the field to understand the current situation and plan future enterprises accordingly.
