Numerical modeling of the dynamic variation in multiphase CH4 during CO2 enhanced gas recovery from depleted shale reservoirs
Jun LIU , Ye ZHANG , Lijun CHENG , Zhaohui LU , Chunlin ZENG , Peng ZHAO
Front. Earth Sci. ›› 2021, Vol. 15 ›› Issue (4) : 790 -802.
Numerical modeling of the dynamic variation in multiphase CH4 during CO2 enhanced gas recovery from depleted shale reservoirs
Regarding CO2 enhanced shale gas recovery, this work focuses on changes in the multiphase (free/adsorbed) CH4 in the process of CO2 enhanced shale gas recovery, by utilizing a rigorous numerical model with real geological parameters. This work studies nine injection well (IW) and CH4 production well (PW) combinations of CO2 to determine the influence of IW and PW locations on the dynamic interaction of multiphase CH4 during 10000 d of CO2 injection. The results indicate that the content of both the adsorbed CH4 and free CH4 is strongly variable before (and during) the CO2-CH4 displacement. In addition, during the simulation process, the proportion of the adsorbed CH4 among all extracted CH4 phases dynamically increases first and then tends to stabilize at 70%–80%. Moreover, the IW-PWs combinations significantly affect the outcomes of CO2 enhanced shale gas recovery – for both the proportion of adsorbed/free CH4 and the recovery efficiency. A longer IW-PW distance enables more adsorbed CH4 to be recovered but results in a lower efficiency of shale gas recovery. Basically, a shorter IW-PWs distance helps recover CH4 via CO2 injection if the IW targets the bottom layer of the Wufeng-Longmaxi shale formation. This numerical work expands the knowledge of CO2 enhanced gas recovery from depleted shale reservoirs.
CO2-CH4 displacement / free gas / Longmaxi shale / CH4 desorption / numerical simulation
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Higher Education Press
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