Since hydrate resources play a part of the stratigraphic framework structure in sediments,establishing a safe and economic method for hydrates exploitation remains the primary challenge to this day.Among the proposed ...Since hydrate resources play a part of the stratigraphic framework structure in sediments,establishing a safe and economic method for hydrates exploitation remains the primary challenge to this day.Among the proposed methods,the spontaneous displacement of CH_(4) from hydrate cages by CO_(2) seems to be a perfect mechanism to address gas production and CO_(2) storage,especially in today's strong demand for carbon reduction and replacing clean energy.After extensive lab researches,in the past decade,injecting a mixture of CO_(2) and small molecule gas has become a key means to enhance displacement efficiency and has great potential for application.However,there is a lack of in-depth research on gas flow in the reservoir,while the injected gas always passes through low-saturated hydrate areas with high permeability and then occurs gas channel in a short term,finally resulting in the decreases in gas production efficiency and produced gas quality.Therefore,we explored a new injection-production mode of alternate injection of N2 and CO_(2) in order to fully coordinate the advantages of N_(2) in enhanced hydrate decomposition and CO_(2) in solid storage and heat compensation.These alternate"taking"and"storing"processes perfectly repair the problem of the gas channel,achieving self-regulation effect of CH_(4) recovery and CO_(2) storage.The 3-D experimental results show that compared to the mixed gas injection,CH_(4) recovery is increased by>50%and CO_(2) storage is increased by>70%.Additionally,this alternate injection mode presented a better performance in CH_(4) concentration of produced gas and showed outstanding N_(2) utilization efficiency.Further,we analyzed its self-adaptive gas flow mechanism and proposed an application model of"one injection and multiple production".We look forward to this study accelerating the application of CO_(2)-CH_(4) replacement technology.展开更多
The permeability and its horizontal anisotropy induce a critical influence on staged CH_(4) output inhibition process.However,a quantitative evaluation of this influence has been rarely reported in the literature.In t...The permeability and its horizontal anisotropy induce a critical influence on staged CH_(4) output inhibition process.However,a quantitative evaluation of this influence has been rarely reported in the literature.In this work,the impact of horizontal anisotropic permeability on CO_(2)-ECBM was numerically investigated.The variation in the staged CH_(4) output inhibition was analyzed.The ideal displacement profile of the CO_(2)-ECBM process was established for the first time.Moreover,the variation in CH_(4) output of different wellbores was discussed.The results showed that 1)low-permeable or weak-anisotropic reservoirs were not conducive to enhanced CH_(4) recovery owing to long inhibition time(>1091 days)and high inhibition level(>36.9%).As permeability and anisotropy increased,due to the accelerated seepage of free water,the hysteresis time and inhibition time could decrease to as short as 5 days and 87 days,respectively,and the inhibition level could weaken to as low as 5.00%.Additionally,the CH_(4) output and CO_(2) injection could increase significantly.2)Nevertheless,high permeability and strong anisotropy easily induced CO_(2) breakthrough,resulting in lower CH_(4) production,CO_(2) injection and CO_(2) storage than expected.While maintaining high efficiency of CO_(2) storage(>99%),upregulating CO_(2) breakthrough concentration from 10%to 20%might ease the unfavorable trend.3)Along the direction of fluid flow,the ideal displacement profile consisted of CO_(2) enriched bank,CO_(2) and CH_(4) mixed bank,CH_(4) enriched bank,and water enriched bank,whereas a remarkable gap in the displacement profiles of the dominant and non-dominant seepage directions was observed.4)The potential of CH_(4) output might vary greatly among different wellbores.The producers along the dominant seepage direction held more potential for CH_(4) recovery in the short-term,while those along the non-dominant seepage direction avoided becoming invalid only if a long-time injection measure was taken for the injectors.These findings pave the way to understand fluid seepage in real complex reservoirs during CO_(2)-ECBM and conduct further field projects.展开更多
Regarding CO_(2)enhanced shale gas recovery,this work focuses on changes in the multiphase(free/adsorbed)CH_(4)in the process of CO_(2)enhanced shale gas recovery,by utilizing a rigorous numerical model with real geol...Regarding CO_(2)enhanced shale gas recovery,this work focuses on changes in the multiphase(free/adsorbed)CH_(4)in the process of CO_(2)enhanced shale gas recovery,by utilizing a rigorous numerical model with real geological parameters.This work studies nine injection well(IW)and CH_(4)production well(PW)combinations of CO_(2)to determine the influence of IW and PW locations on the dynamic interaction of multiphase CH_(4)during 10000 d of CO_(2)injection.The results indicate that the content of both the adsorbed CH_(4)and free CH_(4)is strongly variable before(and during)the CO_(2)-CH_(4)displacement.In addition,during the simulation process,the proportion of the adsorbed CH_(4)among all extracted CH_(4)phases dynamically increases first and then tends to stabilize at 70%-80%.Moreover,the IW-PWs combinations signifi-cantly affect the outcomes of CO_(2)enhanced shale gas recovery-for both the proportion of adsorbed/free CH_(4)and the recovery efficiency.A longer IW-PW distance enables more adsorbed CH_(4)to be recovered but results in a lower efficiency of shale gas recovery.Basically,a shorter IW-PWs distance helps recover CH_(4)via CO_(2)injection if the IW targets the bottom layer of the Wufeng-Longmaxi shale formation.This numerical work expands the knowl-edge of CO_(2)enhanced gas recovery from depleted shale reservoirs.展开更多
基金financially supported by the National Natural Science Foundation of ChinaChina(Nos.22378424,22127812,U20B6005,52004136)+1 种基金the Science Foundation of China University of Petroleum,Beijing(No.2462023BJRC017)Hunan Provincial Department of Education Scientific Research Project(No.22B0310)。
文摘Since hydrate resources play a part of the stratigraphic framework structure in sediments,establishing a safe and economic method for hydrates exploitation remains the primary challenge to this day.Among the proposed methods,the spontaneous displacement of CH_(4) from hydrate cages by CO_(2) seems to be a perfect mechanism to address gas production and CO_(2) storage,especially in today's strong demand for carbon reduction and replacing clean energy.After extensive lab researches,in the past decade,injecting a mixture of CO_(2) and small molecule gas has become a key means to enhance displacement efficiency and has great potential for application.However,there is a lack of in-depth research on gas flow in the reservoir,while the injected gas always passes through low-saturated hydrate areas with high permeability and then occurs gas channel in a short term,finally resulting in the decreases in gas production efficiency and produced gas quality.Therefore,we explored a new injection-production mode of alternate injection of N2 and CO_(2) in order to fully coordinate the advantages of N_(2) in enhanced hydrate decomposition and CO_(2) in solid storage and heat compensation.These alternate"taking"and"storing"processes perfectly repair the problem of the gas channel,achieving self-regulation effect of CH_(4) recovery and CO_(2) storage.The 3-D experimental results show that compared to the mixed gas injection,CH_(4) recovery is increased by>50%and CO_(2) storage is increased by>70%.Additionally,this alternate injection mode presented a better performance in CH_(4) concentration of produced gas and showed outstanding N_(2) utilization efficiency.Further,we analyzed its self-adaptive gas flow mechanism and proposed an application model of"one injection and multiple production".We look forward to this study accelerating the application of CO_(2)-CH_(4) replacement technology.
基金the National Natural Science Foundation of China(Grant No.42141012)the National Key R&D Program of China(No.2018YFB0605600)the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD).
文摘The permeability and its horizontal anisotropy induce a critical influence on staged CH_(4) output inhibition process.However,a quantitative evaluation of this influence has been rarely reported in the literature.In this work,the impact of horizontal anisotropic permeability on CO_(2)-ECBM was numerically investigated.The variation in the staged CH_(4) output inhibition was analyzed.The ideal displacement profile of the CO_(2)-ECBM process was established for the first time.Moreover,the variation in CH_(4) output of different wellbores was discussed.The results showed that 1)low-permeable or weak-anisotropic reservoirs were not conducive to enhanced CH_(4) recovery owing to long inhibition time(>1091 days)and high inhibition level(>36.9%).As permeability and anisotropy increased,due to the accelerated seepage of free water,the hysteresis time and inhibition time could decrease to as short as 5 days and 87 days,respectively,and the inhibition level could weaken to as low as 5.00%.Additionally,the CH_(4) output and CO_(2) injection could increase significantly.2)Nevertheless,high permeability and strong anisotropy easily induced CO_(2) breakthrough,resulting in lower CH_(4) production,CO_(2) injection and CO_(2) storage than expected.While maintaining high efficiency of CO_(2) storage(>99%),upregulating CO_(2) breakthrough concentration from 10%to 20%might ease the unfavorable trend.3)Along the direction of fluid flow,the ideal displacement profile consisted of CO_(2) enriched bank,CO_(2) and CH_(4) mixed bank,CH_(4) enriched bank,and water enriched bank,whereas a remarkable gap in the displacement profiles of the dominant and non-dominant seepage directions was observed.4)The potential of CH_(4) output might vary greatly among different wellbores.The producers along the dominant seepage direction held more potential for CH_(4) recovery in the short-term,while those along the non-dominant seepage direction avoided becoming invalid only if a long-time injection measure was taken for the injectors.These findings pave the way to understand fluid seepage in real complex reservoirs during CO_(2)-ECBM and conduct further field projects.
基金supported by the Project funded by China Postdoctoral Science Foundation(No.2020M683253)the Key Laboratory of Shale Gas Exploration,Ministry of Natural Resources(No.KLSGE-MLR-202003)the National Natural Science Foundation of China(Grant No.51704197).
文摘Regarding CO_(2)enhanced shale gas recovery,this work focuses on changes in the multiphase(free/adsorbed)CH_(4)in the process of CO_(2)enhanced shale gas recovery,by utilizing a rigorous numerical model with real geological parameters.This work studies nine injection well(IW)and CH_(4)production well(PW)combinations of CO_(2)to determine the influence of IW and PW locations on the dynamic interaction of multiphase CH_(4)during 10000 d of CO_(2)injection.The results indicate that the content of both the adsorbed CH_(4)and free CH_(4)is strongly variable before(and during)the CO_(2)-CH_(4)displacement.In addition,during the simulation process,the proportion of the adsorbed CH_(4)among all extracted CH_(4)phases dynamically increases first and then tends to stabilize at 70%-80%.Moreover,the IW-PWs combinations signifi-cantly affect the outcomes of CO_(2)enhanced shale gas recovery-for both the proportion of adsorbed/free CH_(4)and the recovery efficiency.A longer IW-PW distance enables more adsorbed CH_(4)to be recovered but results in a lower efficiency of shale gas recovery.Basically,a shorter IW-PWs distance helps recover CH_(4)via CO_(2)injection if the IW targets the bottom layer of the Wufeng-Longmaxi shale formation.This numerical work expands the knowl-edge of CO_(2)enhanced gas recovery from depleted shale reservoirs.
