Simulation of thermal-reactive-compositional flow processes is fundamental to the thermal recovery of ultra-heavy hydrocarbon resources,and a typical oilfield practice is the in-situ conversion process(ICP)implemented...Simulation of thermal-reactive-compositional flow processes is fundamental to the thermal recovery of ultra-heavy hydrocarbon resources,and a typical oilfield practice is the in-situ conversion process(ICP)implemented in oil shale exploitation.However,accurately capturing the intricate flow dynamics of ICP requires a large number of fine-scale grid-blocks,which renders ICP simulations computationally expensive.Apart from that,plenty of oil shale reservoirs contain natural fractures or require hydraulic fracturing to enhance fluid mobility,creating further challenges in modeling pyrolysis reactions in both rock matrices and fractures.Targeted at the above issues,this work proposes a novel dual-model dualgrid upscaling(DDU)method specifically designed for solid-based thermal-reactive-compositional flow simulations in fractured porous media.Unlike existing upscaling techniques,the DDU method incorporates the upscaling of fracture grids using the embedded discrete fracture modeling(EDFM)approach and introduces a new concept of simplified models to approximate fine-scale results,which are used to correct reaction rates in coarse-scale grids.This method uniquely achieves efficient upscaling for both matrix and fracture grids,supports both open-source and commercial simulation platforms without modifying source codes,and is validated through 3D ICP models with natural fractures.The results indicate that the application of the DDU method can provide a close match with the fine-scale simulation results.Moreover,the DDU method has drastically improved the computational efficiency and speeded up the fine-scale simulation by 396-963 times.Therefore,the proposed DDU method has achieved marked computational savings while maintaining high simulation accuracy,which is significant for the development efficiency and production forecasting of oil shale reservoirs.展开更多
This paper presents an integrated study from fracture propagation modeling to gas flow modeling and a correlation analysis to explore the key controlling factors of intensive volume fracturing.The fracture propagation...This paper presents an integrated study from fracture propagation modeling to gas flow modeling and a correlation analysis to explore the key controlling factors of intensive volume fracturing.The fracture propagation model takes into account the interaction between hydraulic fracture and natural fracture by means of the displacement discontinuity method(DDM)and the Picard iterative method.The shale gas flow considers multiple transport mechanisms,and the flow in the fracture network is handled by the embedded discrete fracture model(EDFM).A series of numerical simulations are conducted to analyze the effects of the cluster number,stage spacing,stress difference coefficient,and natural fracture distribution on the stimulated fracture area,fractal dimension,and cumulative gas production,and their correlation coefficients are obtained.The results show that the most influential factors to the stimulated fracture area are the stress difference ratio,stage spacing,and natural fracture density,while those to the cumulative gas production are the stress difference ratio,natural fracture density,and cluster number.This indicates that the stress condition dominates the gas production,and employing intensive volume fracturing(by properly increasing the cluster number)is beneficial for improving the final cumulative gas production.展开更多
As a promising enhanced gas recovery technique,CO_(2)huff-n-puff has attracted great attention recently.However,hydraulic fracture deformation hysteresis is rarely considered,and its effect on CO_(2)huff-n-puff perfor...As a promising enhanced gas recovery technique,CO_(2)huff-n-puff has attracted great attention recently.However,hydraulic fracture deformation hysteresis is rarely considered,and its effect on CO_(2)huff-n-puff performance is not well understood.In this study,we present a fully coupled multi-component flow and geomechanics model for simulating CO_(2)huff-n-puff in shale gas reservoirs considering hydraulic fracture deformation hysteresis.Specifically,a shale gas reservoir after hydraulic fracturing is modeled using an efficient hybrid model incorporating an embedded discrete fracture model(EDFM),multiple porosity model,and single porosity model.In flow equations,Fick’s law,extended Langmuir isotherms,and the Peng-Robinson equation of state are used to describe the molecular diffusion,multi-component adsorption,and gas properties,respectively.In relation to geomechanics,a path-dependent constitutive law is applied for the hydraulic fracture deformation hysteresis.The finite volume method(FVM)and the stabilized extended finite element method(XFEM)are applied to discretize the flow and geomechanics equations,respectively.We then solve the coupled model using the fixed-stress split iterative method.Finally,we verify the presented method using several numerical examples,and apply it to investigate the effect of hydraulic fracture deformation hysteresis on CO_(2)huff-n-puff performance in a 3D shale gas reservoir.Numerical results show that hydraulic fracture deformation hysteresis has some negative effects on CO_(2)huff-n-puff performance.The effects are sensitive to the initial conductivity of hydraulic fracture,production pressure,starting time of huff-n-puff,injection pressure,and huff-n-puff cycle number.展开更多
This study extends an integrated field characterization in Eagle Ford by optimizing the numerical reservoir simulation of highly representative complex fractured systems through embedded discrete fracture modeling(EDF...This study extends an integrated field characterization in Eagle Ford by optimizing the numerical reservoir simulation of highly representative complex fractured systems through embedded discrete fracture modeling(EDFM). The bottom-hole flowing pressure was history-matched and the field production was forecasted after screening complex fracture scenarios with more than 100 000 fracture planes based on their propped-type. This work provided a greater understanding of the impact of complex-fractures proppant efficiency on the production. After compaction tables were included for each propped-type fracture group, the estimated pressure depletion showed that the effective drainage area can be smaller than the complex fracture network if modeled and screened by the EDFM method rather than unstructured gridding technique. The essential novel value of this work is the capability to couple EDFM with third-party fracture propagation simulation automatically, considering proppant intensity variation along the complex fractured systems. Thus, this work is pioneer to model complex fracture propagation and well interference accurately from fracture diagnostics and pseudo 3 D fracture propagation outcomes for multiple full wellbores to capture well completion effectiveness after myriads of sharper field simulation cases with EDFM.展开更多
Carbon dioxide geological sequestration is an effective method to reduce the content of greenhouse gases in the atmosphere of our planet.This process can also be used to improve the production of oil reservoirs by mix...Carbon dioxide geological sequestration is an effective method to reduce the content of greenhouse gases in the atmosphere of our planet.This process can also be used to improve the production of oil reservoirs by mixing carbon dioxide and crude oil.In the present study,a differential separation experiment(DL)based on actual crude oil components is used to simulate such a process.The results show that after mixing,the viscosity and density of reservoir fluid decrease and the volume coefficient increase,indicating that the pre buried gas induces fluid expansion and an improvement of the fluid rheological properties.These effects are interpreted using a pore scale model based on real scanning electron microscopy(SEM).The results show that increasing the pressure and reducing the viscosity are beneficial to increasing the micro oil displacement efficiency.Moreover,these effects can improve the production in the target area and slow down the decline of the formation pressure.Furthermore,in the case of fracture development in the reservoir(due to CO_(2)injection before exploitation),the risk of gas channelling,induced by the displacement pressure difference between injection and production wells,is avoided.展开更多
Continental shale oil reservoirs,characterized by numerous bedding planes and micro-nano scale pores,feature significantly higher stress sensitivity compared to other types of reservoirs.However,research on suitable s...Continental shale oil reservoirs,characterized by numerous bedding planes and micro-nano scale pores,feature significantly higher stress sensitivity compared to other types of reservoirs.However,research on suitable stress sensitivity characterization models is still limited.In this study,three commonly used stress sensitivity models for shale oil reservoirs were considered,and experiments on representative core samples were conducted.By fitting and comparing the data,the“exponential model”was identified as a characterization model that accurately represents stress sensitivity in continental shale oil reservoirs.To validate the accuracy of the model,a two-phase seepage mathematical model for shale oil reservoirs coupled with the exponential model was introduced.The model was discretely solved using the finite volume method,and its accuracy was verified through the commercial simulator CMG.The study evaluated the productivity of a typical horizontal well under different engineering,geological,and fracture conditions.The results indicate that considering stress sensitivity leads to a 13.57%reduction in production for the same matrix permeability.Additionally,as the fracture half-length and the number of fractures increase,and the bottomhole flowing pressure decreases,the reservoir stress sensitivity becomes higher.展开更多
Appropriate well spacing is crucial for the efficient development of shale reservoirs,as it is closely related to the degree of resource uti-lization.Well spacing design is influenced by both fracturing processes and ...Appropriate well spacing is crucial for the efficient development of shale reservoirs,as it is closely related to the degree of resource uti-lization.Well spacing design is influenced by both fracturing processes and geological characteristics.While increasing well density can enhance reservoir recovery,it may lead to higher investment costs and significant well interference issues.In this study,we adopted an integrated geologicaleengineering approach,combining fracture propagation simulation,EDFM(Embedded Discrete Fracture Modeling),and numerical simulation methods to comprehensively analyze well interference under different well spacings in shale condensate reservoirs.Development well spacing was optimized using the degree of resource utilization and well interference rate as key indicators.There are three main research findings:(1)The geological engineering integration approach allows for differentiated well spacing according to specific research areas.Combining this integrated approach with EDFM and leveraging quantitative evaluation,we have developed an efficient and precise methodology for well spacing optimization.(2)When well spacing is less than the length of hydraulic fractures,inter-well fractures exhibit an entangled pattern,reducing the effectiveness of fracturing treatments and causing severe well interference.As well spacing increases,interference between fractures from different wells diminishes,but unstimulated volumes gradually emerge,leading to a decrease in reservoir recovery.(3)Considering both well interference and resource utilization,a well spacing of 400 m is recommended in the study area.At this spacing,interference between hydraulic fractures from different wells is minimal.After 10 years of production,the estimated reservoir recovery is 39.16%,with a production rate of 25.58%and a well interference rate of 13.58%.These research outcomes provide valuable insights for optimizing the well spacing of hydraulic fractured horizontal wells in shale condensate reservoirs.展开更多
Characterizing natural fractures has a decisive effect on production forecasts in fractured oil and gas reservoirs.Discrete Fracture Networks(DFN)constitutes the main modeling framework for fractured geosystems.Howeve...Characterizing natural fractures has a decisive effect on production forecasts in fractured oil and gas reservoirs.Discrete Fracture Networks(DFN)constitutes the main modeling framework for fractured geosystems.However,myriads of uncertainties are enclosed prior modeling representative stochastic or deterministic DFN ensembles.This paper presents a novel methodology for DFN calibration and an efficacious field application,which incorporatesWell-testing interpretation,Embedded Discrete Fracture Model(EDFM)framework,and numerical reservoir simulation.The proposed workflow starts with the DFN generation from seismic data,imaging logging data and core data.After multiple DFNs are modeled,well-test analysis is employed to calibrate the intrinsic properties of fractures at different locations.Then,these fracture networks are characterized dynamically by EDFM,which promotes capturing the optimal fracture model quickly screened.Finally,pressure and production history match are reached for the DFN realization that honors the optimal fracture model.展开更多
基金the financial support from the National Science Foundation of China(No.52374063 and No.52204065)the Natural Science Foundation of Shandong Province,China(No.ZR2023ME049 and No.ZR2021JQ18)the Fundamental Research Funds for the Central Universities,China(24CX06017A)。
文摘Simulation of thermal-reactive-compositional flow processes is fundamental to the thermal recovery of ultra-heavy hydrocarbon resources,and a typical oilfield practice is the in-situ conversion process(ICP)implemented in oil shale exploitation.However,accurately capturing the intricate flow dynamics of ICP requires a large number of fine-scale grid-blocks,which renders ICP simulations computationally expensive.Apart from that,plenty of oil shale reservoirs contain natural fractures or require hydraulic fracturing to enhance fluid mobility,creating further challenges in modeling pyrolysis reactions in both rock matrices and fractures.Targeted at the above issues,this work proposes a novel dual-model dualgrid upscaling(DDU)method specifically designed for solid-based thermal-reactive-compositional flow simulations in fractured porous media.Unlike existing upscaling techniques,the DDU method incorporates the upscaling of fracture grids using the embedded discrete fracture modeling(EDFM)approach and introduces a new concept of simplified models to approximate fine-scale results,which are used to correct reaction rates in coarse-scale grids.This method uniquely achieves efficient upscaling for both matrix and fracture grids,supports both open-source and commercial simulation platforms without modifying source codes,and is validated through 3D ICP models with natural fractures.The results indicate that the application of the DDU method can provide a close match with the fine-scale simulation results.Moreover,the DDU method has drastically improved the computational efficiency and speeded up the fine-scale simulation by 396-963 times.Therefore,the proposed DDU method has achieved marked computational savings while maintaining high simulation accuracy,which is significant for the development efficiency and production forecasting of oil shale reservoirs.
基金supported by the National Natural Science Foundation of China(Nos.52274038,5203401042174143)+1 种基金the Taishan Scholars Project(No.tsqnz20221140)the Open Fund of State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation(Southwest Petroleum University)of China(No.PLN2020-5)。
文摘This paper presents an integrated study from fracture propagation modeling to gas flow modeling and a correlation analysis to explore the key controlling factors of intensive volume fracturing.The fracture propagation model takes into account the interaction between hydraulic fracture and natural fracture by means of the displacement discontinuity method(DDM)and the Picard iterative method.The shale gas flow considers multiple transport mechanisms,and the flow in the fracture network is handled by the embedded discrete fracture model(EDFM).A series of numerical simulations are conducted to analyze the effects of the cluster number,stage spacing,stress difference coefficient,and natural fracture distribution on the stimulated fracture area,fractal dimension,and cumulative gas production,and their correlation coefficients are obtained.The results show that the most influential factors to the stimulated fracture area are the stress difference ratio,stage spacing,and natural fracture density,while those to the cumulative gas production are the stress difference ratio,natural fracture density,and cluster number.This indicates that the stress condition dominates the gas production,and employing intensive volume fracturing(by properly increasing the cluster number)is beneficial for improving the final cumulative gas production.
基金This work is supported by the National Natural Sci‐ence Foundation of China(Nos.52004321,52034010,and 12131014)the Natural Science Foundation of Shandong Province,China(No.ZR2020QE116)the Fundamental Research Funds for the Central Universities,China(Nos.20CX06025A and 21CX06031A).
文摘As a promising enhanced gas recovery technique,CO_(2)huff-n-puff has attracted great attention recently.However,hydraulic fracture deformation hysteresis is rarely considered,and its effect on CO_(2)huff-n-puff performance is not well understood.In this study,we present a fully coupled multi-component flow and geomechanics model for simulating CO_(2)huff-n-puff in shale gas reservoirs considering hydraulic fracture deformation hysteresis.Specifically,a shale gas reservoir after hydraulic fracturing is modeled using an efficient hybrid model incorporating an embedded discrete fracture model(EDFM),multiple porosity model,and single porosity model.In flow equations,Fick’s law,extended Langmuir isotherms,and the Peng-Robinson equation of state are used to describe the molecular diffusion,multi-component adsorption,and gas properties,respectively.In relation to geomechanics,a path-dependent constitutive law is applied for the hydraulic fracture deformation hysteresis.The finite volume method(FVM)and the stabilized extended finite element method(XFEM)are applied to discretize the flow and geomechanics equations,respectively.We then solve the coupled model using the fixed-stress split iterative method.Finally,we verify the presented method using several numerical examples,and apply it to investigate the effect of hydraulic fracture deformation hysteresis on CO_(2)huff-n-puff performance in a 3D shale gas reservoir.Numerical results show that hydraulic fracture deformation hysteresis has some negative effects on CO_(2)huff-n-puff performance.The effects are sensitive to the initial conductivity of hydraulic fracture,production pressure,starting time of huff-n-puff,injection pressure,and huff-n-puff cycle number.
文摘This study extends an integrated field characterization in Eagle Ford by optimizing the numerical reservoir simulation of highly representative complex fractured systems through embedded discrete fracture modeling(EDFM). The bottom-hole flowing pressure was history-matched and the field production was forecasted after screening complex fracture scenarios with more than 100 000 fracture planes based on their propped-type. This work provided a greater understanding of the impact of complex-fractures proppant efficiency on the production. After compaction tables were included for each propped-type fracture group, the estimated pressure depletion showed that the effective drainage area can be smaller than the complex fracture network if modeled and screened by the EDFM method rather than unstructured gridding technique. The essential novel value of this work is the capability to couple EDFM with third-party fracture propagation simulation automatically, considering proppant intensity variation along the complex fractured systems. Thus, this work is pioneer to model complex fracture propagation and well interference accurately from fracture diagnostics and pseudo 3 D fracture propagation outcomes for multiple full wellbores to capture well completion effectiveness after myriads of sharper field simulation cases with EDFM.
基金Thanks for the support of a major national special project during the 13th Five-Year Plan period,“Chemical Flooding Technology for Offshore Oil Fields”(No.2016ZX05025-003)“Heavy Oil Chemical Flooding Mechanism and Simulation Technology Research”(No.2019-YXKJ-008)Research on Source Sink Matching Technology and Scheme of Regional CCUs Project(2021-ZYZL-XNY-01),etc.
文摘Carbon dioxide geological sequestration is an effective method to reduce the content of greenhouse gases in the atmosphere of our planet.This process can also be used to improve the production of oil reservoirs by mixing carbon dioxide and crude oil.In the present study,a differential separation experiment(DL)based on actual crude oil components is used to simulate such a process.The results show that after mixing,the viscosity and density of reservoir fluid decrease and the volume coefficient increase,indicating that the pre buried gas induces fluid expansion and an improvement of the fluid rheological properties.These effects are interpreted using a pore scale model based on real scanning electron microscopy(SEM).The results show that increasing the pressure and reducing the viscosity are beneficial to increasing the micro oil displacement efficiency.Moreover,these effects can improve the production in the target area and slow down the decline of the formation pressure.Furthermore,in the case of fracture development in the reservoir(due to CO_(2)injection before exploitation),the risk of gas channelling,induced by the displacement pressure difference between injection and production wells,is avoided.
基金supported by the China Postdoctoral Science Foundation(2021M702304)Natural Science Foundation of Shandong Province(ZR2021QE260).
文摘Continental shale oil reservoirs,characterized by numerous bedding planes and micro-nano scale pores,feature significantly higher stress sensitivity compared to other types of reservoirs.However,research on suitable stress sensitivity characterization models is still limited.In this study,three commonly used stress sensitivity models for shale oil reservoirs were considered,and experiments on representative core samples were conducted.By fitting and comparing the data,the“exponential model”was identified as a characterization model that accurately represents stress sensitivity in continental shale oil reservoirs.To validate the accuracy of the model,a two-phase seepage mathematical model for shale oil reservoirs coupled with the exponential model was introduced.The model was discretely solved using the finite volume method,and its accuracy was verified through the commercial simulator CMG.The study evaluated the productivity of a typical horizontal well under different engineering,geological,and fracture conditions.The results indicate that considering stress sensitivity leads to a 13.57%reduction in production for the same matrix permeability.Additionally,as the fracture half-length and the number of fractures increase,and the bottomhole flowing pressure decreases,the reservoir stress sensitivity becomes higher.
文摘Appropriate well spacing is crucial for the efficient development of shale reservoirs,as it is closely related to the degree of resource uti-lization.Well spacing design is influenced by both fracturing processes and geological characteristics.While increasing well density can enhance reservoir recovery,it may lead to higher investment costs and significant well interference issues.In this study,we adopted an integrated geologicaleengineering approach,combining fracture propagation simulation,EDFM(Embedded Discrete Fracture Modeling),and numerical simulation methods to comprehensively analyze well interference under different well spacings in shale condensate reservoirs.Development well spacing was optimized using the degree of resource utilization and well interference rate as key indicators.There are three main research findings:(1)The geological engineering integration approach allows for differentiated well spacing according to specific research areas.Combining this integrated approach with EDFM and leveraging quantitative evaluation,we have developed an efficient and precise methodology for well spacing optimization.(2)When well spacing is less than the length of hydraulic fractures,inter-well fractures exhibit an entangled pattern,reducing the effectiveness of fracturing treatments and causing severe well interference.As well spacing increases,interference between fractures from different wells diminishes,but unstimulated volumes gradually emerge,leading to a decrease in reservoir recovery.(3)Considering both well interference and resource utilization,a well spacing of 400 m is recommended in the study area.At this spacing,interference between hydraulic fractures from different wells is minimal.After 10 years of production,the estimated reservoir recovery is 39.16%,with a production rate of 25.58%and a well interference rate of 13.58%.These research outcomes provide valuable insights for optimizing the well spacing of hydraulic fractured horizontal wells in shale condensate reservoirs.
基金This researchwas funded by“CNPC Science and technology project:Fine evaluation and prediction technology for complex reservoirs in overseas natural gas reservoirs,grant number 2018D-4305”.
文摘Characterizing natural fractures has a decisive effect on production forecasts in fractured oil and gas reservoirs.Discrete Fracture Networks(DFN)constitutes the main modeling framework for fractured geosystems.However,myriads of uncertainties are enclosed prior modeling representative stochastic or deterministic DFN ensembles.This paper presents a novel methodology for DFN calibration and an efficacious field application,which incorporatesWell-testing interpretation,Embedded Discrete Fracture Model(EDFM)framework,and numerical reservoir simulation.The proposed workflow starts with the DFN generation from seismic data,imaging logging data and core data.After multiple DFNs are modeled,well-test analysis is employed to calibrate the intrinsic properties of fractures at different locations.Then,these fracture networks are characterized dynamically by EDFM,which promotes capturing the optimal fracture model quickly screened.Finally,pressure and production history match are reached for the DFN realization that honors the optimal fracture model.
