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 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
Given that a large amount of crude oil remains on the surface of rocks and is difficult to produce after conventional waterflooding,a new superwetting oil displacement system incorporating the synergy between a hydrox...Given that a large amount of crude oil remains on the surface of rocks and is difficult to produce after conventional waterflooding,a new superwetting oil displacement system incorporating the synergy between a hydroxyl anion compound(1OH-1C)and an extended surfactant(S-C_(13)PO_(13)S)was designed.The interfacial tension,contact angle and emulsification performance of the system were measured.The oil displacement effects and improved oil recovery(IOR)mechanisms of 1OH-1C,S-C_(13)PO_(13)S and their compound system were investigated by microscopic visualization oil displacement experiments and core displacement experiments.The results show that 1OH-1C creates a superwetting interface and electrostatic separation pressure on the solid surface,which destroys the strong interactions between crude oil and quartz to peel off the oil film.S-C_(13)PO_(13)S has low interfacial tension,which can promote the flow of remaining oil and emulsify it into oil-in-water emulsions.The compound system of 1OH-1C and S-C_(13)PO_(13)S has both superwettability and low IFT,which can effectively improve oil recovery through a synergistic effect.The oil displacement experiment of low-permeability natural core shows that the compound solution can increase the oil recovery by 16.4 percentage points after waterflooding.This new high-efficiency system is promising for greatly improving oil recovery in low-permeability reservoirs.展开更多
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
Hydrogels are widely used in reservoir flow control to enhanced oil recovery.However,challenges such as environmental contamination from conventional crosslinkers,poor solubility of crosslinking agents,and short gelat...Hydrogels are widely used in reservoir flow control to enhanced oil recovery.However,challenges such as environmental contamination from conventional crosslinkers,poor solubility of crosslinking agents,and short gelation times under high-temperature conditions(e.g.,150℃)have hindered their practical application.Herein,we present the synthesis of amine-functionalized carbon quantum dots(NH_(2)-CQDs),which act as both a nano-crosslinker and a nano-reinforcing agent within hydrogel systems.The NH_(2)-CQDs-incorporated hydrogel can remain stability for 300 days under the conditions of a mineralization degree of 2.11×10^(4)mg/mL and 170℃,and has high tensile strength(371 kPa),good toughness(49.6 kJ/m~3),excellent viscoelasticity(G'=960 Pa,G"=460 Pa)and shear resistance.In addition,NH_(2)-CQDs adds many hydroxyl groups to the hydrogel,which can be attached to the surface of various substances.At the same time,micro-nano capsules containing NH_(2)-CQDs were formed by self-assembly of hydrophobic SiO_(2)on water droplets,the NH_(2)-CQDs solution is encapsulated in a capsule,and when stimulated by external conditions(temperature,pH,surfactant),the capsule releases the NH_(2)-CQDs solution,this method greatly delays the crosslinking time between polymer and crosslinker at high temperature.Under the condition of 170℃and pH=7,the gelation time of 10%hydrophobic SiO_(2)coated hydrogel is 44 times that of uncoated hydrogel,which can be effectively used for deep formation flow control,and CQD give hydrogels fluorescence properties that can be used for underground signal tracking.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
CO_(2)-enhanced oil recovery(CO_(2)-EOR)is an economically viable carbon capture,utilization,and storage(CCUS)technique that is widely practiced and greatly contributes to the achievement of carbon-neutral cities.Howe...CO_(2)-enhanced oil recovery(CO_(2)-EOR)is an economically viable carbon capture,utilization,and storage(CCUS)technique that is widely practiced and greatly contributes to the achievement of carbon-neutral cities.However,studies on CO_(2)-EOR source-sink matching involving different emission sources,different carbon capture rates,and stepwise CO_(2)pipeline construction are scarce.Considering four types of carbon sources,including coal-fired power,iron and steel,cement,and chemical plants,with different CO_(2)capture rates(85%,90%,95%,and 100%,respectively),and using a five-phased construction plan with a 25-year build-up period,we developed a method for quantifying carbon emissions from different sources,calculating the effective storage of carbon in CO_(2)-EOR and optimizing CO_(2)-EOR source-sink matching to reduce project costs.Using the Subei Basin in the Jiangsu Province,China,as a case study,we calculated the theoretical CO_(2)-EOR storage to be 1.7408×10^(8)t and the effective CO_(2)-EOR storage to be 0.435×10^(8)t.We analyzed the completion rate of transportation pipelines,the number of connected carbon sources,and the mass of CO_(2)stored,as well as the cost-effectiveness and sensitivity.Implementation of CO_(2)-EOR effectively reduced the total cost of source-sink matching in the five-stage 25-year construction approach.The reduction of CO_(2)capture rates had no effect on the value of oil repelling.The capture cost significantly affected the total cost of source-sink matching,and the impacts of the carbon sources on the total cost were in the order coal-fired power>iron and steel>cement>chemical plants.This study provides an innovative tool for evaluating the CO_(2)storage potential of CO_(2)-EOR and provides an important framework for implementing CO_(2)-EOR and planning CCUS projects in the Subei Basin and similar regions.展开更多
The tight-tuff heavy oil reservoir exhibits severe heterogeneity and is characterized by high density,high viscosity,and a high wax content,posing significant challenges for its development.While CO_(2)huffand-puff(H-...The tight-tuff heavy oil reservoir exhibits severe heterogeneity and is characterized by high density,high viscosity,and a high wax content,posing significant challenges for its development.While CO_(2)huffand-puff(H-n-P)enhances oil recovery,these reservoirs struggle with low displacement efficiency.This study proposes a method that combines CO_(2)with an oil-soluble viscosity reducer to improve displacement efficiency in the H-n-P process for tight-tuff heavy oil reservoirs.It also focuses on evaluating pore utilization limits and optimizing the injection strategy.Core samples and crude oil from the TH oilfield(a tight-tuff heavy oil reservoir)were used to conduct online NMR core flooding experiments,including depletion development,water,CO_(2),and HDC(CO_(2)combined with an oil-soluble viscosity reducer)H-n-P injection processes.A single-porosity model accurately reflecting its geological characteristics was developed using the GEM component simulator within the CMG numerical simulation software to investigate the optimized schemes and the enhanced oil recovery potential for a tight-tuff heavy oil reservoir in the TH oilfield.This model was utilized to evaluate the impact of various injection strategies on oilfield recovery efficiency.The study was designed and implemented with five distinct injection schemes.Results showed that oil was produced primarily from large and medium pores during the depletion stage,while water H-n-P,with CO_(2)H-n-P,first targeted macropores,then mesopores,and micropores.The lower pore utilization limit was 0.0267μm.In the HDC H-n-P process,most oil was recovered from water-flooded pores.Still,HDC's lower injection capacity increased the pore utilization limit to 0.03μm,making micropore recovery difficult.Experimental and modeling results suggest that the optimal develo p ment plan for the TH oilfield is one cycle of HDC H-n-P followed by two cycles of CO_(2)H-n-P.This strategy leverages HDC's ability to promote water and oil recovery in the early stage and mass transfer and extraction capacity of CO_(2)in later cycles.Additionally,the characteristics of CO_(2)and HDC H-n-P processes,pore utilization,and recoverable oil(at the pore scale)were evaluated.The results of this study are crucial for refining the reservoir development plan.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
Supercritical carbon dioxide （scCO2） microemulsion was formed by supercritical CO2, H20, sodium bis（2-ethylhexyl） sulfosuccinate （AOT, surfactant） and C2HsOH （co-surfactant） under pressures higher than 8 MPa a...Supercritical carbon dioxide （scCO2） microemulsion was formed by supercritical CO2, H20, sodium bis（2-ethylhexyl） sulfosuccinate （AOT, surfactant） and C2HsOH （co-surfactant） under pressures higher than 8 MPa at 45 ℃. The fundamental characteristics of the scCO2 microemulsion and the minimum miscibility pressure （MMP） with Daqing oil were investigated with a high-pressure falling sphere viscometer, a high-pressure interfacial tension meter, a PVT cell and a slim tube test. The mechanism of the scCO2 microemulsion for enhancing oil recovery is discussed. The results showed that the viscosity and density of the scCO2 microemulsion were higher than those of the scCO2 fluid at the same pressure and temperature. The results of interfacial tension and slim tube tests indicated that the MMP of the scCO2 microemulsion and crude oil was lower than that of the scCO2 and crude oil at 45 ℃. It is the combined action of viscosity, density and MMP which made the oil recovery efficiency of the scCO2 microemulsion higher than that of the scCO2 fluid.展开更多
In recent years,production from tight oil reservoirs has increasingly supplemented production from conventional oil resources.Oil-wet formations account for a considerable proportion of tight oil reservoirs.Surfactant...In recent years,production from tight oil reservoirs has increasingly supplemented production from conventional oil resources.Oil-wet formations account for a considerable proportion of tight oil reservoirs.Surfactant can change wettability and reduce interfacial tension,thus resulting in a better oil recovery.In this manuscript,a nonionic surfactant was introduced for tight oil-wet reservoirs.The oil recovery in the oil-wet sandstone due to spontaneous imbibition was 8.59%lower than that of the waterwet sandstone due to surfactant.The 0.1%surfactant solution corresponded to the highest imbibition recovery rate of 27.02%from the oil-wet sample.With the surfactant treatment,the treated core quickly changed from weakly oil-wet to weakly water-wet.The capillary force acted as the driving force and promoted imbibition.The optimal surfactant adsorption quantity in the oil-wet sandstone was observed in the sample at concentrations ranging from 0.1%to 0.3%,which also corresponded to the highest oil recovery.Analysis of the inverse Bond number NB-1 suggested that the driving force was gravity for brine imbibition in the oil-wet cores and that it was capillary force for surfactant imbibition in the oil-wet cores.When the surfactant concentration was lower than the critical micelle concentration,the surfactant concentration was negatively correlated with the inverse Bond number and positively correlated with the oil recovery rate.When the surfactant concentration was higher than the critical micelle concentration,the oil recovery increased with a smaller interfacial tension.Nuclear magnetic resonance suggested that the movable pore and pore throat size in the oil-wet sample decreased from 0.363 mm in the untreated rock to 0.326 mm with the surfactant treatment,which indicated that the surfactant improved the flow capacity of the oil.The findings of this study can help to better understand the adsorption impact of surfactants on the characteristics of the oil/water and solid/liquid interfaces.The imbibition mechanism in oil-wet tight sandstone reservoirs was further revealed.These systematic approaches help to select appropriate surfactants for better recovery in oil-wet tight sandstone reservoirs through imbibition.展开更多
Surfactant-based oil recovery processes are employed to lower the interfacial tension in immiscible displacement processes,change the wettability of rock to a more water-wet system and emulsify the oil to displace it ...Surfactant-based oil recovery processes are employed to lower the interfacial tension in immiscible displacement processes,change the wettability of rock to a more water-wet system and emulsify the oil to displace it in subsurface porous media.Furthermore,these phenomena can reduce the capillary pressure and enhance spontaneous imbibition.The key factors affecting such immiscible displacement process are temperature,salinity and p H of the fluids,surfactant concentration and adsorption.Therefore,before any surfactant flooding process is applied,extensive studies of fluid-fluid and rock-fluid interactions are needed.The use of other chemicals along with surfactants in chemical enhanced oil recovery(c EOR)processes have been widely considered to exploit the synergy of individual chemicals and complement the weakness arises from each of them during immiscible displacement of fluids in porous media.Therefore,such combinations of chemicals lead to alkaline-surfactant(AS),surfactantpolymer(SP),alkaline-surfactant-polymer(ASP),and nanoparticle-surfactant(NS)flooding processes,among others.In this review study,we categorised the role and displacement mechanisms of surfactants and discussed the key factors to be considered for analysing the fluid displacement in porous media.展开更多
Climate researchers have observed that the carbon dioxide （CO2） concentration in the atmosphere have been growing significantly over the past century. CO2 from energy represents about 75% of the greenhouse gas （GHG...Climate researchers have observed that the carbon dioxide （CO2） concentration in the atmosphere have been growing significantly over the past century. CO2 from energy represents about 75% of the greenhouse gas （GHG） emissions for Annex B （Developed） countries, and over 60% of global emissions. Because of impermeable cap rocks hydrocarbon reservoirs are able to sequester CO〉 In addition, due to high-demand for oil worldwide, injection of CO2 is a useful way to enhance oil production. Hence, applying an efficient method to co-optimize CO2 storage and oil production is vital. Lack of suitable optimization techniques in the past led most multi-objective optimization problems to be tackled in the same way as a single objective optimization issue. However, there are some basic differences between the multi and single objective optimization methods. In this study, by using a non- dominated sorting genetic algorithm （NSGA-II） for an oil reservoir, some appropriate scenarios are proposed based on simultaneous gas storage and enhanced oil recovery optimization. The advantages of this method allow us to amend production scenarios after implementing the optimization process, by regarding the variation of economic parameters such as oil price and CO2 tax. This leads to reduced risks and time duration of making new decisions based on upcoming situations.展开更多
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.
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.
基金Supported by the National Key R&D Program of China(2019YFA0708700,2023YFF0614100)CNPC Major Science and Technology Project(2021ZZ01,2023ZZ04).
文摘Given that a large amount of crude oil remains on the surface of rocks and is difficult to produce after conventional waterflooding,a new superwetting oil displacement system incorporating the synergy between a hydroxyl anion compound(1OH-1C)and an extended surfactant(S-C_(13)PO_(13)S)was designed.The interfacial tension,contact angle and emulsification performance of the system were measured.The oil displacement effects and improved oil recovery(IOR)mechanisms of 1OH-1C,S-C_(13)PO_(13)S and their compound system were investigated by microscopic visualization oil displacement experiments and core displacement experiments.The results show that 1OH-1C creates a superwetting interface and electrostatic separation pressure on the solid surface,which destroys the strong interactions between crude oil and quartz to peel off the oil film.S-C_(13)PO_(13)S has low interfacial tension,which can promote the flow of remaining oil and emulsify it into oil-in-water emulsions.The compound system of 1OH-1C and S-C_(13)PO_(13)S has both superwettability and low IFT,which can effectively improve oil recovery through a synergistic effect.The oil displacement experiment of low-permeability natural core shows that the compound solution can increase the oil recovery by 16.4 percentage points after waterflooding.This new high-efficiency system is promising for greatly improving oil recovery in low-permeability reservoirs.
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support and funding from the National Natural Science Foundation of China(No.52174047)。
文摘Hydrogels are widely used in reservoir flow control to enhanced oil recovery.However,challenges such as environmental contamination from conventional crosslinkers,poor solubility of crosslinking agents,and short gelation times under high-temperature conditions(e.g.,150℃)have hindered their practical application.Herein,we present the synthesis of amine-functionalized carbon quantum dots(NH_(2)-CQDs),which act as both a nano-crosslinker and a nano-reinforcing agent within hydrogel systems.The NH_(2)-CQDs-incorporated hydrogel can remain stability for 300 days under the conditions of a mineralization degree of 2.11×10^(4)mg/mL and 170℃,and has high tensile strength(371 kPa),good toughness(49.6 kJ/m~3),excellent viscoelasticity(G'=960 Pa,G"=460 Pa)and shear resistance.In addition,NH_(2)-CQDs adds many hydroxyl groups to the hydrogel,which can be attached to the surface of various substances.At the same time,micro-nano capsules containing NH_(2)-CQDs were formed by self-assembly of hydrophobic SiO_(2)on water droplets,the NH_(2)-CQDs solution is encapsulated in a capsule,and when stimulated by external conditions(temperature,pH,surfactant),the capsule releases the NH_(2)-CQDs solution,this method greatly delays the crosslinking time between polymer and crosslinker at high temperature.Under the condition of 170℃and pH=7,the gelation time of 10%hydrophobic SiO_(2)coated hydrogel is 44 times that of uncoated hydrogel,which can be effectively used for deep formation flow control,and CQD give hydrogels fluorescence properties that can be used for underground signal tracking.
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Natural Science Foundation of Jiangsu Province,Grant/Award Number:BK20231488National Natural Science Foundation of China,Grant/Award Numbers:52378083,52078481。
文摘CO_(2)-enhanced oil recovery(CO_(2)-EOR)is an economically viable carbon capture,utilization,and storage(CCUS)technique that is widely practiced and greatly contributes to the achievement of carbon-neutral cities.However,studies on CO_(2)-EOR source-sink matching involving different emission sources,different carbon capture rates,and stepwise CO_(2)pipeline construction are scarce.Considering four types of carbon sources,including coal-fired power,iron and steel,cement,and chemical plants,with different CO_(2)capture rates(85%,90%,95%,and 100%,respectively),and using a five-phased construction plan with a 25-year build-up period,we developed a method for quantifying carbon emissions from different sources,calculating the effective storage of carbon in CO_(2)-EOR and optimizing CO_(2)-EOR source-sink matching to reduce project costs.Using the Subei Basin in the Jiangsu Province,China,as a case study,we calculated the theoretical CO_(2)-EOR storage to be 1.7408×10^(8)t and the effective CO_(2)-EOR storage to be 0.435×10^(8)t.We analyzed the completion rate of transportation pipelines,the number of connected carbon sources,and the mass of CO_(2)stored,as well as the cost-effectiveness and sensitivity.Implementation of CO_(2)-EOR effectively reduced the total cost of source-sink matching in the five-stage 25-year construction approach.The reduction of CO_(2)capture rates had no effect on the value of oil repelling.The capture cost significantly affected the total cost of source-sink matching,and the impacts of the carbon sources on the total cost were in the order coal-fired power>iron and steel>cement>chemical plants.This study provides an innovative tool for evaluating the CO_(2)storage potential of CO_(2)-EOR and provides an important framework for implementing CO_(2)-EOR and planning CCUS projects in the Subei Basin and similar regions.
基金funded by the Natural Science Foundation of Beijing Municipality(3232028)the National Natural Science Foundation of China(52274053)the National Foreign Expert Individual Project(H20240045)。
文摘The tight-tuff heavy oil reservoir exhibits severe heterogeneity and is characterized by high density,high viscosity,and a high wax content,posing significant challenges for its development.While CO_(2)huffand-puff(H-n-P)enhances oil recovery,these reservoirs struggle with low displacement efficiency.This study proposes a method that combines CO_(2)with an oil-soluble viscosity reducer to improve displacement efficiency in the H-n-P process for tight-tuff heavy oil reservoirs.It also focuses on evaluating pore utilization limits and optimizing the injection strategy.Core samples and crude oil from the TH oilfield(a tight-tuff heavy oil reservoir)were used to conduct online NMR core flooding experiments,including depletion development,water,CO_(2),and HDC(CO_(2)combined with an oil-soluble viscosity reducer)H-n-P injection processes.A single-porosity model accurately reflecting its geological characteristics was developed using the GEM component simulator within the CMG numerical simulation software to investigate the optimized schemes and the enhanced oil recovery potential for a tight-tuff heavy oil reservoir in the TH oilfield.This model was utilized to evaluate the impact of various injection strategies on oilfield recovery efficiency.The study was designed and implemented with five distinct injection schemes.Results showed that oil was produced primarily from large and medium pores during the depletion stage,while water H-n-P,with CO_(2)H-n-P,first targeted macropores,then mesopores,and micropores.The lower pore utilization limit was 0.0267μm.In the HDC H-n-P process,most oil was recovered from water-flooded pores.Still,HDC's lower injection capacity increased the pore utilization limit to 0.03μm,making micropore recovery difficult.Experimental and modeling results suggest that the optimal develo p ment plan for the TH oilfield is one cycle of HDC H-n-P followed by two cycles of CO_(2)H-n-P.This strategy leverages HDC's ability to promote water and oil recovery in the early stage and mass transfer and extraction capacity of CO_(2)in later cycles.Additionally,the characteristics of CO_(2)and HDC H-n-P processes,pore utilization,and recoverable oil(at the pore scale)were evaluated.The results of this study are crucial for refining the reservoir development plan.
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.
基金support from the National Natural Science Fund (50904073)the CNPC Science and Technology Innovation Fund (2008D-5006-02-06)
文摘Supercritical carbon dioxide （scCO2） microemulsion was formed by supercritical CO2, H20, sodium bis（2-ethylhexyl） sulfosuccinate （AOT, surfactant） and C2HsOH （co-surfactant） under pressures higher than 8 MPa at 45 ℃. The fundamental characteristics of the scCO2 microemulsion and the minimum miscibility pressure （MMP） with Daqing oil were investigated with a high-pressure falling sphere viscometer, a high-pressure interfacial tension meter, a PVT cell and a slim tube test. The mechanism of the scCO2 microemulsion for enhancing oil recovery is discussed. The results showed that the viscosity and density of the scCO2 microemulsion were higher than those of the scCO2 fluid at the same pressure and temperature. The results of interfacial tension and slim tube tests indicated that the MMP of the scCO2 microemulsion and crude oil was lower than that of the scCO2 and crude oil at 45 ℃. It is the combined action of viscosity, density and MMP which made the oil recovery efficiency of the scCO2 microemulsion higher than that of the scCO2 fluid.
基金financially supported by the National Key R&D Program of China(No.2019YFA0708700)National Science Fund of China(No.51804327,51834010)+1 种基金Climb Taishan Scholar Program in Shandong Province(No.tspd20161004)the Fundamental Research Funds for the Central Universities(No.18CX02026A,24720182026A)。
文摘In recent years,production from tight oil reservoirs has increasingly supplemented production from conventional oil resources.Oil-wet formations account for a considerable proportion of tight oil reservoirs.Surfactant can change wettability and reduce interfacial tension,thus resulting in a better oil recovery.In this manuscript,a nonionic surfactant was introduced for tight oil-wet reservoirs.The oil recovery in the oil-wet sandstone due to spontaneous imbibition was 8.59%lower than that of the waterwet sandstone due to surfactant.The 0.1%surfactant solution corresponded to the highest imbibition recovery rate of 27.02%from the oil-wet sample.With the surfactant treatment,the treated core quickly changed from weakly oil-wet to weakly water-wet.The capillary force acted as the driving force and promoted imbibition.The optimal surfactant adsorption quantity in the oil-wet sandstone was observed in the sample at concentrations ranging from 0.1%to 0.3%,which also corresponded to the highest oil recovery.Analysis of the inverse Bond number NB-1 suggested that the driving force was gravity for brine imbibition in the oil-wet cores and that it was capillary force for surfactant imbibition in the oil-wet cores.When the surfactant concentration was lower than the critical micelle concentration,the surfactant concentration was negatively correlated with the inverse Bond number and positively correlated with the oil recovery rate.When the surfactant concentration was higher than the critical micelle concentration,the oil recovery increased with a smaller interfacial tension.Nuclear magnetic resonance suggested that the movable pore and pore throat size in the oil-wet sample decreased from 0.363 mm in the untreated rock to 0.326 mm with the surfactant treatment,which indicated that the surfactant improved the flow capacity of the oil.The findings of this study can help to better understand the adsorption impact of surfactants on the characteristics of the oil/water and solid/liquid interfaces.The imbibition mechanism in oil-wet tight sandstone reservoirs was further revealed.These systematic approaches help to select appropriate surfactants for better recovery in oil-wet tight sandstone reservoirs through imbibition.
基金the Faculty of Engineering University of Khartoum,Sudan,for the financial support of his studies at the University of Aberdeen
文摘Surfactant-based oil recovery processes are employed to lower the interfacial tension in immiscible displacement processes,change the wettability of rock to a more water-wet system and emulsify the oil to displace it in subsurface porous media.Furthermore,these phenomena can reduce the capillary pressure and enhance spontaneous imbibition.The key factors affecting such immiscible displacement process are temperature,salinity and p H of the fluids,surfactant concentration and adsorption.Therefore,before any surfactant flooding process is applied,extensive studies of fluid-fluid and rock-fluid interactions are needed.The use of other chemicals along with surfactants in chemical enhanced oil recovery(c EOR)processes have been widely considered to exploit the synergy of individual chemicals and complement the weakness arises from each of them during immiscible displacement of fluids in porous media.Therefore,such combinations of chemicals lead to alkaline-surfactant(AS),surfactantpolymer(SP),alkaline-surfactant-polymer(ASP),and nanoparticle-surfactant(NS)flooding processes,among others.In this review study,we categorised the role and displacement mechanisms of surfactants and discussed the key factors to be considered for analysing the fluid displacement in porous media.
文摘Climate researchers have observed that the carbon dioxide （CO2） concentration in the atmosphere have been growing significantly over the past century. CO2 from energy represents about 75% of the greenhouse gas （GHG） emissions for Annex B （Developed） countries, and over 60% of global emissions. Because of impermeable cap rocks hydrocarbon reservoirs are able to sequester CO〉 In addition, due to high-demand for oil worldwide, injection of CO2 is a useful way to enhance oil production. Hence, applying an efficient method to co-optimize CO2 storage and oil production is vital. Lack of suitable optimization techniques in the past led most multi-objective optimization problems to be tackled in the same way as a single objective optimization issue. However, there are some basic differences between the multi and single objective optimization methods. In this study, by using a non- dominated sorting genetic algorithm （NSGA-II） for an oil reservoir, some appropriate scenarios are proposed based on simultaneous gas storage and enhanced oil recovery optimization. The advantages of this method allow us to amend production scenarios after implementing the optimization process, by regarding the variation of economic parameters such as oil price and CO2 tax. This leads to reduced risks and time duration of making new decisions based on upcoming situations.
