Sorption of methane and CO2 for enhanced coalbed methane recovery and carbon dioxide sequestration

Sequestration of COin deep and unmineable coal seams is one of the attractive alternatives to reduce its at- mospheric concentration.Injection of COin 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,COwas injected into the coals and subsequently they were depressurized again.Desorption of methane after the injections was studied,to investigate the ability of COto displace and enhance the recovery of methane from the coals.The coals exhibited varying behavior of adsorption of COand release of methane.For one coal,the release of methane was enhanced by injection of CO,suggesting preferential adsorption of COand desorption of methane.For the other two coals,COinjection did not produce incremental methane initially,as there was initial resistance to methane release.However with continued COinjection,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.