Sorption of methane and CO 2 for enhanced coalbed methane recovery and carbon dioxide sequestration

Abstract

Sequestration of CO 2 in deep and unmineable coal seams is one of the attractive alternatives to reduce its at- mospheric concentration. Injection of CO 2 in coal seams may help in enhancing the recovery of coalbed methane. An exper- imental study has been carried out using coal samples from three different coal seams, to evaluate the enhanced gas recovery and sequestration potential of these coals. The coals were first saturated with methane and then by depressurization some of the adsorbed methane was desorbed. After partial desorption, CO 2 was injected into the coals and subsequently they were depressurized again. Desorption of methane after the injections was studied, to investigate the ability of CO 2 to displace and enhance the recovery of methane from the coals. The coals exhibited varying behavior of adsorption of CO 2 and release of methane. For one coal, the release of methane was enhanced by injection of CO 2, suggesting preferential adsorption of CO 2 and desorption of methane. For the other two coals, CO 2 injection did not produce incremental methane initially, as there was initial resistance to methane release. However with continued CO 2 injection, most of the remaining methane was produced. The study suggested that preferential sorption behavior of coal and enhanced gas recovery pattern could not be generalized for all coals.