The injectivity of coalbed CO2 injection wells

Though it may be possible to enhance methane production from coal by injecting CO2, because coal is poorly permeable it is usually necessary to inject under fracturing conditions to achieve acceptable injectivity. Concomitantly, the process of replacing methane by the injected CO2 causes the matrix to swell. These two processes—the fracturing of the coal and the swelling—have opposite effect on the injectivity.