The Effect of CO2-CH4 Sorption Phenomena on Methane Recovery of Coalbed Methane

Abstract

ECBM is an important enhancing technique to produce additional gas. The production behavior in ECBM process is mainly affected by the sorption characteristics. In order to understand the mechanism of sorption characteristics of CO2 and methane, this paper investigated the methane recovery by the effect of Langmuir pressure and volume related with sorption process. As a result of CO2 injection, as the Langmuir pressure of CH4 increases while the Langmuir volume decreases, CO2 breakthrough time is delayed since pressure gradient is small between the wells. We also found that the replacement efficiency between CO2 and methane is sensitively affected as the Langmuir pressure and volume are varied. Due to the impacts of CO2 BT and replacement efficiency, the methane recovery at CO2 BT time is changed by the Langmuir pressure and volume. As an another characteristics of sorption, sorption time of methane was examined in terms of methane recovery. With the increase in sorption time of methane, replacement efficiency is decreased and CO2 BT is delayed. This counter effect yields no significant change in methane recovery.