The Effect of Aquifer Condition on Methane Recovery for CO2 Injection in Coalbed

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.