A seepage-geomechanical coupled embedded fracture flow model has been established for multi-field coupled simulation in tight oil reservoirs,revealing the patterns of change in pressure field,seepage field,and stress ...A seepage-geomechanical coupled embedded fracture flow model has been established for multi-field coupled simulation in tight oil reservoirs,revealing the patterns of change in pressure field,seepage field,and stress field after long-term water injection in tight oil reservoirs.Based on this,a technique for enhanced oil recovery(EOR)combining multi-field reconstruction and combination of displacement and imbibition in tight oil reservoirs has been proposed.The study shows that after long-term water flooding for tight oil development,the pressure diffusion range is limited,making it difficult to establish an effective displacement system.The variation in geostress exhibits diversity,with the change in horizontal minimum principal stress being greater than that in horizontal maximum principal stress,and the variation around the injection wells being more significant than that around the production wells.The deflection of geostress direction around injection wells is also large.The technology for EOR through multi-field reconstruction and combination of displacement and imbibition employs water injection wells converted to production and large-scale fracturing techniques to restructure the artificial fracture network system.Through a full lifecycle energy replenishment method of pre-fracturing energy supplementation,energy increase during fracturing,well soaking for energy storage,and combination of displacement and imbibition,it effectively addresses the issue of easy channeling of the injection medium and difficult energy replenishment after large-scale fracturing.By intensifying the imbibition effect through the coordination of multiple wells,it reconstructs the combined system of displacement and imbibition under a complex fracture network,transitioning from avoiding fractures to utilizing them,thereby improving microscopic sweep and oil displacement efficiencies.Field application in Block Yuan 284 of the Huaqing Oilfield in the Ordos Basin has demonstrated that this technology increases the recovery factor by 12 percentage points,enabling large scale and efficient development of tight oil.展开更多
Based on the microfluidic technology,a microscopic visualization model was used to simulate the gas injection process in the initial construction stage and the bottom water invasion/gas injection process in the cyclic...Based on the microfluidic technology,a microscopic visualization model was used to simulate the gas injection process in the initial construction stage and the bottom water invasion/gas injection process in the cyclical injection-production stage of the underground gas storage(UGS)rebuilt from water-invaded gas reservoirs.Through analysis of the gas-liquid contact stabilization mechanism,flow and occurrence,the optimal control method for lifecycle efficient operation of UGS was explored.The results show that in the initial construction stage of UGS,the action of gravity should be fully utilized by regulating the gas injection rate,so as to ensure the macroscopically stable migration of the gas-liquid contact,and greatly improve the gas sweeping capacity,providing a large pore space for gas storage in the subsequent cyclical injection-production stage.In the cyclical injection-production stage of UGS,a constant gas storage and production rate leads to a low pore space utilization.Gradually increasing the gas storage and production rate,that is,transitioning from small volume to large volume,can continuously break the hydraulic equilibrium of the remaining fluid in the porous media,which then expands the pore space and flow channels.This is conducive to the expansion of UGS capacity and efficiency for purpose of peak shaving and supply guarantee.展开更多
Based on practices of CO_(2) flooding tests in China and abroad,the recovery factor of carbon dioxide capture,utilization in displacing oil and storage(CCUS-EOR)in permanent sequestration scenario has been investigate...Based on practices of CO_(2) flooding tests in China and abroad,the recovery factor of carbon dioxide capture,utilization in displacing oil and storage(CCUS-EOR)in permanent sequestration scenario has been investigated in this work.Under the background of carbon neutrality,carbon dioxide injection into geological bodies should pursue the goal of permanent sequestration for effective carbon emission reduction.Hence,CCUS-EOR is an ultimate development method for oil reservoirs to maximize oil recovery.The limit recovery factor of CCUS-EOR development mode is put forward,the connotation differences between it and ultimate recovery factor and economically reasonable recovery factor are clarified.It is concluded that limit recovery factor is achievable with mature supporting technical base for the whole process of CCUS-EOR.Based on statistics of practical data of CO_(2) flooding projects in China and abroad such as North H79 block CO_(2) flooding pilot test at small well spacing in Jilin Oilfield etc.,the empirical relationship between the oil recovery factor of miscible CO_(2) flooding and cumulative CO_(2) volume injected is obtained by regression.Combined with the concept of oil production rate multiplier of gas flooding,a reservoir engineering method calculating CO_(2) flooding recovery factor under any miscible degree is established by derivation.It is found that when the cumulative CO_(2) volume injected is 1.5 times the hydrocarbon pore volume(HCPV),the relative deviation and the absolute difference between the recovery percentage and the limit recovery factor are less than 5%and less than 2.0 percentage points respectively.The limit recovery factor of CCUS-EOR can only be approached by large pore volume(PV)injection based on the technology of expanding swept volume.It needs to be realized from three aspects:large PV injection scheme design,enhancing miscibility degree and continuously expanding swept volume of injected CO_(2).展开更多
基金Supported by the Joint Fund Project of the National Natural Science Foundation of China(U22B2075).
文摘A seepage-geomechanical coupled embedded fracture flow model has been established for multi-field coupled simulation in tight oil reservoirs,revealing the patterns of change in pressure field,seepage field,and stress field after long-term water injection in tight oil reservoirs.Based on this,a technique for enhanced oil recovery(EOR)combining multi-field reconstruction and combination of displacement and imbibition in tight oil reservoirs has been proposed.The study shows that after long-term water flooding for tight oil development,the pressure diffusion range is limited,making it difficult to establish an effective displacement system.The variation in geostress exhibits diversity,with the change in horizontal minimum principal stress being greater than that in horizontal maximum principal stress,and the variation around the injection wells being more significant than that around the production wells.The deflection of geostress direction around injection wells is also large.The technology for EOR through multi-field reconstruction and combination of displacement and imbibition employs water injection wells converted to production and large-scale fracturing techniques to restructure the artificial fracture network system.Through a full lifecycle energy replenishment method of pre-fracturing energy supplementation,energy increase during fracturing,well soaking for energy storage,and combination of displacement and imbibition,it effectively addresses the issue of easy channeling of the injection medium and difficult energy replenishment after large-scale fracturing.By intensifying the imbibition effect through the coordination of multiple wells,it reconstructs the combined system of displacement and imbibition under a complex fracture network,transitioning from avoiding fractures to utilizing them,thereby improving microscopic sweep and oil displacement efficiencies.Field application in Block Yuan 284 of the Huaqing Oilfield in the Ordos Basin has demonstrated that this technology increases the recovery factor by 12 percentage points,enabling large scale and efficient development of tight oil.
文摘Based on the microfluidic technology,a microscopic visualization model was used to simulate the gas injection process in the initial construction stage and the bottom water invasion/gas injection process in the cyclical injection-production stage of the underground gas storage(UGS)rebuilt from water-invaded gas reservoirs.Through analysis of the gas-liquid contact stabilization mechanism,flow and occurrence,the optimal control method for lifecycle efficient operation of UGS was explored.The results show that in the initial construction stage of UGS,the action of gravity should be fully utilized by regulating the gas injection rate,so as to ensure the macroscopically stable migration of the gas-liquid contact,and greatly improve the gas sweeping capacity,providing a large pore space for gas storage in the subsequent cyclical injection-production stage.In the cyclical injection-production stage of UGS,a constant gas storage and production rate leads to a low pore space utilization.Gradually increasing the gas storage and production rate,that is,transitioning from small volume to large volume,can continuously break the hydraulic equilibrium of the remaining fluid in the porous media,which then expands the pore space and flow channels.This is conducive to the expansion of UGS capacity and efficiency for purpose of peak shaving and supply guarantee.
基金Supported by CNPC Science and Technology Project(kt2022-8-202021ZZ01).
文摘Based on practices of CO_(2) flooding tests in China and abroad,the recovery factor of carbon dioxide capture,utilization in displacing oil and storage(CCUS-EOR)in permanent sequestration scenario has been investigated in this work.Under the background of carbon neutrality,carbon dioxide injection into geological bodies should pursue the goal of permanent sequestration for effective carbon emission reduction.Hence,CCUS-EOR is an ultimate development method for oil reservoirs to maximize oil recovery.The limit recovery factor of CCUS-EOR development mode is put forward,the connotation differences between it and ultimate recovery factor and economically reasonable recovery factor are clarified.It is concluded that limit recovery factor is achievable with mature supporting technical base for the whole process of CCUS-EOR.Based on statistics of practical data of CO_(2) flooding projects in China and abroad such as North H79 block CO_(2) flooding pilot test at small well spacing in Jilin Oilfield etc.,the empirical relationship between the oil recovery factor of miscible CO_(2) flooding and cumulative CO_(2) volume injected is obtained by regression.Combined with the concept of oil production rate multiplier of gas flooding,a reservoir engineering method calculating CO_(2) flooding recovery factor under any miscible degree is established by derivation.It is found that when the cumulative CO_(2) volume injected is 1.5 times the hydrocarbon pore volume(HCPV),the relative deviation and the absolute difference between the recovery percentage and the limit recovery factor are less than 5%and less than 2.0 percentage points respectively.The limit recovery factor of CCUS-EOR can only be approached by large pore volume(PV)injection based on the technology of expanding swept volume.It needs to be realized from three aspects:large PV injection scheme design,enhancing miscibility degree and continuously expanding swept volume of injected CO_(2).
