Enhanced CBM recovery

Abstract

Abstract The conventional CBM recovery is accomplished by reservoir pressure depletion, which could be detrimental to the economic gas recovery. Enhanced coalbed methane (ECBM) recovery involves injection of nitrogen or carbon dioxide into a CBM reservoir to promote methane desorption without lowering the reservoir pressure. Carbon dioxide injection may provide greater methane recovery than nitrogen because carbon dioxide adsorbs in the coal and releases the methane molecules adsorbed on the coal micropores. CO2-ECBM has an added advantage that carbon dioxide gas can be stored in coal seams (CO2-storage). The field trials have demonstrated that enhanced CBM recovery and simultaneous CO2-storage can be achieved. However, the cost associated with the gas injection and separation is a major impediment to the application of the ECBM recovery processes. A better understanding the extreme complication of physical and thermodynamic phenomena involved in the CO2-storage/ECBM recovery processes is essential in order to establish full confidence in the technology.