Modeling of coal bed methane (CBM) production and CO2 sequestration in coal seams

A mathematical model was developed to predict the coal bed methane (CBM) production and carbon dioxide (CO2) sequestration in a coal seam accounting for the coal seam properties. The model predictions showed that, for a CBM production and dewatering process, the pressure could be reduced from 15.17 MPa to 1.56 MPa and the gas saturation increased up to 50% in 30 years for a 5.4 x 10(5) m(2) of coal formation. For the CO2 sequestration process, the model prediction showed that the CO2 injection rate was first reduced and then slightly recovered over 3 to 13 years of injection, which was also evidenced by the actual in seam data. The model predictions indicated that the sweeping of the water in front of the CO2 flood in the cleat porosity could be important on the loss of injectivity. Further model predictions suggested that the injection rate of CO2 could be about 11 x 10(3) m(3) per day; the injected CO2 would reach the production well, which was separated from the injection well by 826 m, in about 30 years. During this period, about 160 x 10(6) m(3) of CO2 could be stored within a 21.4 x 10(5) m(2) of coal seam with a thickness of 3 m. (C) 2008 Elsevier B.V. All rights reserved.