The purpose of this paper is to investigate the influence of various aquifer conditions on the CO2 displacement efficiency and methane recovery in the coal seam. The movement of CO2 in cleat is sensitively dependent upon aquifer condition as well as sorption characteristics of coal, since the pressure of coalseam is determined based on the position of aquifer. In this study, methane recovery for CO2 injection process was analyzed regarding the contacting position and strength of the aquifer. We ascertained that both methane recovery and CO2 sequestration are inefficient when the hydraulic connection between overlying aquifer and coal seam is strong. This is because buoyancy effect causes gas leakage to the overlying aquifer although CO2 displacing methane has a greater affinity compring to methane. Although the vertical permeability of underlying aquifer is great, the effect of methane recovery and CO2 sequestration are efficiently successful during CO2-ECBM process because the leakage of both the amount of injected CO2 and desorbed methane is negligible. Although the injected CO2 is effetively sequestrated in the edge aquifer case, ECBM recovery shows irregular efficiency in part due to the asymmetrical flow of the injected CO2. It is considered that the design of proper strategies regarding CO2 movement means a lot to the aspect of methane recovery and CO2 sequestration to maximize economic profit.

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