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
Excess water production has become an important issue in the oil and gas extraction process.Preformed particle gels(PPGs),show the capability to control the conformance and reduce excess water cut.However,conventional...Excess water production has become an important issue in the oil and gas extraction process.Preformed particle gels(PPGs),show the capability to control the conformance and reduce excess water cut.However,conventional PPGs have poor mechanical properties and their swollen particles are easily damaged by shearing force when passing through the fractures in formations,meanwhile PPGs can be also degraded into various byproducts,leading to permanent damage to the reservoir permeability after temporary plugging.Herein,a novel type of dual cross-linked PPGs(dPPGs)was designed and synthesized using sodium alginate(SA)and acrylamide(AAm),cross-linked with N,N’-methylenebisacrylamide(MBA)and Fe^(3+).Results show that dPPGs have excellent mechanical properties with a storage modulus up to 86,445 Pa,which is almost 20 times higher than other reported PPGs.Meanwhile,dPPGs can be completely degraded into liquid without any solid residues or byproducts and the viscosity of dPPGs degraded liquid was found to be lower than 5 mPa·s.A laboratory coreflooding test showed that the plugging efficiency of dPPGs was up to 99.83%on open fractures.The obtained results demonstrated that dPPGs could be used as economical and environment-friendly temporary plugging agent with high-strength,self-degradation,thermal stability,and salt stability,thus making it applicable to a wide range of conformance control to enhance oil recovery.展开更多
Horizontal well drilling and multistage hydraulic fracturing have been demonstrated as effective approaches for stimulating oil production in the Bakken tight oil reservoir.However,after multiple years of production,p...Horizontal well drilling and multistage hydraulic fracturing have been demonstrated as effective approaches for stimulating oil production in the Bakken tight oil reservoir.However,after multiple years of production,primary oil recovery in the Bakken is generally less than 10%of the estimated original oil in place.Gas huff‘n’puff(HnP)has been tested in the Bakken Formation as an enhanced oil recovery(EOR)method;however,most field pilot test results showed no significant incremental oil production.One of the factors affecting HnP EOR performance is premature gas breakthrough,which is one of the most critical issues observed in the field because of the presence of interwell fractures.Consequently,injected gas rapidly reaches adjacent production wells without contacting reservoir rock and increasing oil recovery.Proper conformance control is therefore needed to avoid early gas breakthrough and improve EOR performance.In this study,a rich gas EOR pilot in the Bakken was carefully analyzed to collect the essential reservoir and operational data.A simulation model with 16 wells was then developed to reproduce the production history and predict the EOR performance with and without conformance control.EOR operational strategies,including single-and multiple-well HnP,with different gas injection constraints were investigated.The simulation results of single-well HnP without conformance control showed that a rich gas injection rate of at least 10 MMscfd was needed to yield meaningful incremental oil production.The strategy of conformance control via water injection could significantly improve oil production in the HnP well,but injecting an excessive amount of water also leads to water breakthrough and loss of oil production in the offset wells.By analyzing the production performance of the wells individually,the arrangement of wells was optimized for multiple-well HnP EOR.The multiwell results showed that rich gas EOR could improve oil production up to 7.4%by employing conformance control strategies.Furthermore,replaci展开更多
Injecting CO2into hydrocarbon reservoirs can enhance the recovery of hydrocarbon resources,and simultaneously,CO2can be stored in the rese rvoirs,reducing considerable amount of carbon emissions in the atmosphere.Howe...Injecting CO2into hydrocarbon reservoirs can enhance the recovery of hydrocarbon resources,and simultaneously,CO2can be stored in the rese rvoirs,reducing considerable amount of carbon emissions in the atmosphere.However,injected CO_(2)tends to go through fractures,high-permeability channels and streaks present in reservoirs,resulting in inefficient hydrocarbon recovery coupled with low CO_(2)storage performance.Conformance treatments with CO_(2)-resistant crosslinked polymer gels were performed in this study to mitigate the CO_(2)channeling issue and promote the synergy between enhanced oil recovery(EOR) and subsurface sequestration of CO_(2).Based on a typical low-permeability CO_(2)-flooding reservoir in China,studies were performed to investigate the EOR and CO_(2)storage performance with and without conformance treatment.The effect of permeability contrast between the channels and rese rvoir matrices,treatment size,and plugging strength on the efficiency of oil recovery and CO_(2)storage was systematically investigated.The results indicated that after conformance treatments,the CO_(2)channeling problem was mitigated during CO_(2)flooding and storage.The injected CO_(2)was more effectively utilized to recover the hydrocarbons,and entered wider spectrum of pore spaces.Consequently,more CO_(2)was trapped underground.Pronounced factors on the synergy of EOR and CO_(2)storage were figured out.Compared with the treatment size,the CO_(2)storage efficiency was more sensitive to the plugging strength of the conformance treatment materials.This observation was important for conformance treatment design in CCUS-EOR projects.According to this study,the materials should reduce the channel permeability to make the channel/matrix permeability ratio below 30.The results demonstrate the importance of conformance treatment in maximizing the performance of CCUS-EOR process to achieve both oil recovery improvement and efficient carbon storage.This study provides guidelines for successful field applications of CO_(2)transport co展开更多
Injecting CO_(2)into the underground for oil displacement and shortage is an important technique for carbon capture,utilization and storage(CCUS).One of the main problems during the CO_(2)injection is the channeling p...Injecting CO_(2)into the underground for oil displacement and shortage is an important technique for carbon capture,utilization and storage(CCUS).One of the main problems during the CO_(2)injection is the channeling plugging.Finding an effective method for the gas channeling plugging is a critical issue in the CO_(2)EOR process.In this work,an acid-resistance microgel named dispersed particle gel(DPG)was characterized and its stability was tested in the CO_(2)environment.The microgel size selection strategies for the homogeneous and heterogeneous reservoirs were respectively investigated using the single core flooding and three parallel core flooding experiments.Moreover,the comparison of microgel alternate CO_(2)(MAC)injection and water alternate CO_(2)(WAC)injection in the dual core flooding experiments were presented for the investigation of the role of microgel on the conformance control in CO_(2)flooding process.The results have shown that the microgel featured with ANH and CAN groups can keep its morphology after aging 7 days in the CO_(2)environment.Where,the small microgel with unobstructed migration and large microgel with good plugging efficiency for the high permeability zone were respectively featured with the higher recovery factor in homogeneous and heterogeneous conditions,which indicate they are preferred used for the oil displacement and conformance control.Compared to WAC injection,MAC injection had a higher incremental recovery factor of 12.4%.It suggests the acid-resistance microgel would be a good candidate for the conformance control during CO_(2)flooding process.展开更多
High water-cut has become a worldwide challenge for oil production.It requires extensive efforts to process and dispose.This entails expanding water handling facilities and incurring high power consumption costs.Polym...High water-cut has become a worldwide challenge for oil production.It requires extensive efforts to process and dispose.This entails expanding water handling facilities and incurring high power consumption costs.Polymeric microsphere injection is a cost-effective way to deal with excessive water production from subterranean formations.This study reports a laboratory investigation on polymeric microsphere injection in a large volume to identify its in-depth fluid diversion capacity in a porous media with large pore/particle size ratio.The performance of polymeric microsphere injection was evaluated using etched glass micromodels based on the pore network of a natural carbonate rock,which were treated as water-wet or oil-wet micromodels.Waterflooding was conducted to displace oil at reservoir temperature of 95°C,followed by one pore volume of polymeric microsphere injection.Three polymeric microsphere samples with median particle size of 0.05,0.3,and 20μm were used to investigate the impact of particle size of the polymeric microspheres on incremental oil production capacity.Although the polymeric microspheres were much smaller than the pores,additional oil production was observed.The incremental oil production increased with increasing polymeric microsphere concentration and particle size.As a comparison,polymeric microsphere solutions were injected into oil-wet and water-wet micromodels after waterflooding.It was observed that the oil production in oil-wet micromodel was much higher than that in water-wet micromodel.The wettability of micromodels affected the distribution patterns of the remaining oil after waterflooding and further dominated the performance of the microsphere injection.The study supports the applicability of microsphere injection in oil-wet heterogeneous carbonates.展开更多
Oil production and mainte nance are essential issues in naturally fractured reservoirs because they are the largest and most productive on earth.However,they present early water and gas channeling but could be remedia...Oil production and mainte nance are essential issues in naturally fractured reservoirs because they are the largest and most productive on earth.However,they present early water and gas channeling but could be remediated by using foaming agents to control these phenomena through blocking channeling areas.In Mexico these reservoirs have pressure up to 5,500 psi,high temperature up to 200℃,salinity up to400,000 ppm,and hardness up to 250,000 ppm;due to these thermodynamic conditions,there has been no available technology to form stable enough foams.In this work,a foaming supramolecular surfactant with the capability to chelate Ca^(2+)ions is examined.As a result,surfactant monomers are bridged by captured Ca^(2+)cations leading to the formation of high-molecular-weight oligomers,which significantly increment the viscosity of the solution improving the foam stability,and since at this manner the Ca2+cations are no longer available to precipitate as components of solid salts,the foaming supramolecular surfactant also performs as antiscalant.These observations are explained through quantum theoretical modeling.The foam is stable,effectively blocking the gas channels,whereas in presence of oil the foam is broken leading the oil to pass into the wellbore.The characteristic rheological properties of the foam allow its injection into the formation at a range of flow rates,foam qualities,and shear stress to achieve the flooding and the blocking of a variety of fractured carbonate formations,and the change of the wettability of the matrix,which is a desirable behavior in a huff and puff process,as reported in a previous publication about a successful pilot test of this foam.展开更多
Amphiphilic polymer gels are widely used in heterogeneous reservoirs for conformance control technology.However,in high temperature and high salinity of calcium and magnesium reservoirs,amphiphilic polymer gels cannot...Amphiphilic polymer gels are widely used in heterogeneous reservoirs for conformance control technology.However,in high temperature and high salinity of calcium and magnesium reservoirs,amphiphilic polymer gels cannot maintain effective performance.In this work,a novel reinforced amphiphilic polymer gel(F-PADC gel)was prepared by physically mixing polymer solution and fly ash(FA),which is an extremely low cost material.The viscoelasticity and stability of the F-PADC gel were studied by rheometry and micro-rheometry.The reinforced mechanism of FA on amphiphilic polymer gels was revealed.The results show that the addition of FA can make the gel more robust with a denser network structure.On the fifth day,the elastic modulus(G’)increases from 5.2 to 7.0 Pa and the viscosity modulus(G")increases from 0.4 to 0.6 Pa at the frequency of 1 Hz,which improves the viscoelasticity of the gel system.More importantly,the F-PADC gel does not degrade after aging at 85℃for 180 d.And its viscoelasticity increases obviously,G′and G"increase to 110.0 Pa and 3.5 Pa,respectively,showing excellent anti-aging stability.Moreover,FA amphiphilic polymer gels have a good injectivity and a perfect plugging rate of 98.86%,which is better than that of sole amphiphilic polymer gels.This novel mixed FA amphiphilic polymer gels can prove to be a better alternative to conventional polymer gels to enhance oil recovery in high temperature and high salinity reservoirs.展开更多
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.
基金supported by Shanxi Provincial Key Research and Development Project(No.20201102002)the Science Foundation of China University of Petroleum,Beijing(No.2462020BJRC007,2462020YXZZ003)State Key Laboratory of Petroleum Resources and Prospecting,China University of Petroleum(No.PRP/DX-2216)
文摘Excess water production has become an important issue in the oil and gas extraction process.Preformed particle gels(PPGs),show the capability to control the conformance and reduce excess water cut.However,conventional PPGs have poor mechanical properties and their swollen particles are easily damaged by shearing force when passing through the fractures in formations,meanwhile PPGs can be also degraded into various byproducts,leading to permanent damage to the reservoir permeability after temporary plugging.Herein,a novel type of dual cross-linked PPGs(dPPGs)was designed and synthesized using sodium alginate(SA)and acrylamide(AAm),cross-linked with N,N’-methylenebisacrylamide(MBA)and Fe^(3+).Results show that dPPGs have excellent mechanical properties with a storage modulus up to 86,445 Pa,which is almost 20 times higher than other reported PPGs.Meanwhile,dPPGs can be completely degraded into liquid without any solid residues or byproducts and the viscosity of dPPGs degraded liquid was found to be lower than 5 mPa·s.A laboratory coreflooding test showed that the plugging efficiency of dPPGs was up to 99.83%on open fractures.The obtained results demonstrated that dPPGs could be used as economical and environment-friendly temporary plugging agent with high-strength,self-degradation,thermal stability,and salt stability,thus making it applicable to a wide range of conformance control to enhance oil recovery.
基金supported by the U.S.Department of Energy National Energy Technology Laboratory under Award No.DEFE0024233the North Dakota Industrial Commission under the Award Nos.G-04-080(BPOP 2.0)and G-051-98(BPOP 3.0).
文摘Horizontal well drilling and multistage hydraulic fracturing have been demonstrated as effective approaches for stimulating oil production in the Bakken tight oil reservoir.However,after multiple years of production,primary oil recovery in the Bakken is generally less than 10%of the estimated original oil in place.Gas huff‘n’puff(HnP)has been tested in the Bakken Formation as an enhanced oil recovery(EOR)method;however,most field pilot test results showed no significant incremental oil production.One of the factors affecting HnP EOR performance is premature gas breakthrough,which is one of the most critical issues observed in the field because of the presence of interwell fractures.Consequently,injected gas rapidly reaches adjacent production wells without contacting reservoir rock and increasing oil recovery.Proper conformance control is therefore needed to avoid early gas breakthrough and improve EOR performance.In this study,a rich gas EOR pilot in the Bakken was carefully analyzed to collect the essential reservoir and operational data.A simulation model with 16 wells was then developed to reproduce the production history and predict the EOR performance with and without conformance control.EOR operational strategies,including single-and multiple-well HnP,with different gas injection constraints were investigated.The simulation results of single-well HnP without conformance control showed that a rich gas injection rate of at least 10 MMscfd was needed to yield meaningful incremental oil production.The strategy of conformance control via water injection could significantly improve oil production in the HnP well,but injecting an excessive amount of water also leads to water breakthrough and loss of oil production in the offset wells.By analyzing the production performance of the wells individually,the arrangement of wells was optimized for multiple-well HnP EOR.The multiwell results showed that rich gas EOR could improve oil production up to 7.4%by employing conformance control strategies.Furthermore,replaci
基金supported by Science Foundation of China University of Petroleum,Beijing(No.2462022BJRC001,2462021YJRC012)the funding from State Key Laboratory of Petroleum Resources and Prospecting(No.PRP/indep-1-2103)
文摘Injecting CO2into hydrocarbon reservoirs can enhance the recovery of hydrocarbon resources,and simultaneously,CO2can be stored in the rese rvoirs,reducing considerable amount of carbon emissions in the atmosphere.However,injected CO_(2)tends to go through fractures,high-permeability channels and streaks present in reservoirs,resulting in inefficient hydrocarbon recovery coupled with low CO_(2)storage performance.Conformance treatments with CO_(2)-resistant crosslinked polymer gels were performed in this study to mitigate the CO_(2)channeling issue and promote the synergy between enhanced oil recovery(EOR) and subsurface sequestration of CO_(2).Based on a typical low-permeability CO_(2)-flooding reservoir in China,studies were performed to investigate the EOR and CO_(2)storage performance with and without conformance treatment.The effect of permeability contrast between the channels and rese rvoir matrices,treatment size,and plugging strength on the efficiency of oil recovery and CO_(2)storage was systematically investigated.The results indicated that after conformance treatments,the CO_(2)channeling problem was mitigated during CO_(2)flooding and storage.The injected CO_(2)was more effectively utilized to recover the hydrocarbons,and entered wider spectrum of pore spaces.Consequently,more CO_(2)was trapped underground.Pronounced factors on the synergy of EOR and CO_(2)storage were figured out.Compared with the treatment size,the CO_(2)storage efficiency was more sensitive to the plugging strength of the conformance treatment materials.This observation was important for conformance treatment design in CCUS-EOR projects.According to this study,the materials should reduce the channel permeability to make the channel/matrix permeability ratio below 30.The results demonstrate the importance of conformance treatment in maximizing the performance of CCUS-EOR process to achieve both oil recovery improvement and efficient carbon storage.This study provides guidelines for successful field applications of CO_(2)transport co
基金supported by the National Natural Science Foundation of China(52004305)the Postdoctoral Research Foundation of China(2021M693497)the Science Foundation of China University of Petroleum,Beijing(2462020XKBH006)。
文摘Injecting CO_(2)into the underground for oil displacement and shortage is an important technique for carbon capture,utilization and storage(CCUS).One of the main problems during the CO_(2)injection is the channeling plugging.Finding an effective method for the gas channeling plugging is a critical issue in the CO_(2)EOR process.In this work,an acid-resistance microgel named dispersed particle gel(DPG)was characterized and its stability was tested in the CO_(2)environment.The microgel size selection strategies for the homogeneous and heterogeneous reservoirs were respectively investigated using the single core flooding and three parallel core flooding experiments.Moreover,the comparison of microgel alternate CO_(2)(MAC)injection and water alternate CO_(2)(WAC)injection in the dual core flooding experiments were presented for the investigation of the role of microgel on the conformance control in CO_(2)flooding process.The results have shown that the microgel featured with ANH and CAN groups can keep its morphology after aging 7 days in the CO_(2)environment.Where,the small microgel with unobstructed migration and large microgel with good plugging efficiency for the high permeability zone were respectively featured with the higher recovery factor in homogeneous and heterogeneous conditions,which indicate they are preferred used for the oil displacement and conformance control.Compared to WAC injection,MAC injection had a higher incremental recovery factor of 12.4%.It suggests the acid-resistance microgel would be a good candidate for the conformance control during CO_(2)flooding process.
文摘High water-cut has become a worldwide challenge for oil production.It requires extensive efforts to process and dispose.This entails expanding water handling facilities and incurring high power consumption costs.Polymeric microsphere injection is a cost-effective way to deal with excessive water production from subterranean formations.This study reports a laboratory investigation on polymeric microsphere injection in a large volume to identify its in-depth fluid diversion capacity in a porous media with large pore/particle size ratio.The performance of polymeric microsphere injection was evaluated using etched glass micromodels based on the pore network of a natural carbonate rock,which were treated as water-wet or oil-wet micromodels.Waterflooding was conducted to displace oil at reservoir temperature of 95°C,followed by one pore volume of polymeric microsphere injection.Three polymeric microsphere samples with median particle size of 0.05,0.3,and 20μm were used to investigate the impact of particle size of the polymeric microspheres on incremental oil production capacity.Although the polymeric microspheres were much smaller than the pores,additional oil production was observed.The incremental oil production increased with increasing polymeric microsphere concentration and particle size.As a comparison,polymeric microsphere solutions were injected into oil-wet and water-wet micromodels after waterflooding.It was observed that the oil production in oil-wet micromodel was much higher than that in water-wet micromodel.The wettability of micromodels affected the distribution patterns of the remaining oil after waterflooding and further dominated the performance of the microsphere injection.The study supports the applicability of microsphere injection in oil-wet heterogeneous carbonates.
基金supports granted by Instituto Mexicano del Petr oleo (IMP) through the Project Y.00123 “Procesos de RM en yacimientos carbonatados fracturados de alta salinidad y temperatura con base en el dise~no, desarrollo y escalamiento de productos químicos ad hoc”financially supported by the SENER-CONACYT/Hidrocarburos fund through the Project 146735, D.61029 “Dise~no y síntesis de nuevos prototipos de productos químicos multifuncionales con propiedades dispersantes de asfaltenos modificadoras de la mojabilidad y desemulsificantes”
文摘Oil production and mainte nance are essential issues in naturally fractured reservoirs because they are the largest and most productive on earth.However,they present early water and gas channeling but could be remediated by using foaming agents to control these phenomena through blocking channeling areas.In Mexico these reservoirs have pressure up to 5,500 psi,high temperature up to 200℃,salinity up to400,000 ppm,and hardness up to 250,000 ppm;due to these thermodynamic conditions,there has been no available technology to form stable enough foams.In this work,a foaming supramolecular surfactant with the capability to chelate Ca^(2+)ions is examined.As a result,surfactant monomers are bridged by captured Ca^(2+)cations leading to the formation of high-molecular-weight oligomers,which significantly increment the viscosity of the solution improving the foam stability,and since at this manner the Ca2+cations are no longer available to precipitate as components of solid salts,the foaming supramolecular surfactant also performs as antiscalant.These observations are explained through quantum theoretical modeling.The foam is stable,effectively blocking the gas channels,whereas in presence of oil the foam is broken leading the oil to pass into the wellbore.The characteristic rheological properties of the foam allow its injection into the formation at a range of flow rates,foam qualities,and shear stress to achieve the flooding and the blocking of a variety of fractured carbonate formations,and the change of the wettability of the matrix,which is a desirable behavior in a huff and puff process,as reported in a previous publication about a successful pilot test of this foam.
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Amphiphilic polymer gels are widely used in heterogeneous reservoirs for conformance control technology.However,in high temperature and high salinity of calcium and magnesium reservoirs,amphiphilic polymer gels cannot maintain effective performance.In this work,a novel reinforced amphiphilic polymer gel(F-PADC gel)was prepared by physically mixing polymer solution and fly ash(FA),which is an extremely low cost material.The viscoelasticity and stability of the F-PADC gel were studied by rheometry and micro-rheometry.The reinforced mechanism of FA on amphiphilic polymer gels was revealed.The results show that the addition of FA can make the gel more robust with a denser network structure.On the fifth day,the elastic modulus(G’)increases from 5.2 to 7.0 Pa and the viscosity modulus(G")increases from 0.4 to 0.6 Pa at the frequency of 1 Hz,which improves the viscoelasticity of the gel system.More importantly,the F-PADC gel does not degrade after aging at 85℃for 180 d.And its viscoelasticity increases obviously,G′and G"increase to 110.0 Pa and 3.5 Pa,respectively,showing excellent anti-aging stability.Moreover,FA amphiphilic polymer gels have a good injectivity and a perfect plugging rate of 98.86%,which is better than that of sole amphiphilic polymer gels.This novel mixed FA amphiphilic polymer gels can prove to be a better alternative to conventional polymer gels to enhance oil recovery in high temperature and high salinity reservoirs.
