Influence of Shrinkage and Swelling of Coal on Production of Coalbed Methane andSequestration of Carbon Dioxide

摘要

The potential for enhanced methane production andgeologic sequestration of carbon dioxide in unmineablecoal seams needs to be evaluated before large-scalesequestration projects are undertaken. Coal is known tocompetitively adsorb carbon dioxide and methanegases. Laboratory experiments indicate that coal willswell when a gas is adsorbed and shrink when a gas isdesorbed. The swelling and shrinkage may change thecleat porosity and permeability of the coal. This paperdeals with the influence of shrinkage and swelling of coalon the production of methane from, and injection ofcarbon dioxide into, a coalbed reservoir. A threedimensionalswelling and shrinkage model wasdeveloped. This model is based on constitutiveequations that account for coupled fluid pressuredeformationbehavior of a porous medium thatundergoes swelling and shrinkage. The swelling andshrinkage strains are computed on the basis of theamounts of different gases adsorbed or desorbed. Thepermeability of the reservoir is modified by the shrinkageor swelling. The paper presents numerical results on thereservoir performance during injection of carbon dioxidein a previous field test that has been reported in theliterature. The results indicate that coal swelling andshrinkage can influence the production rates andreservoir pressure distribution in the field.