Methane desorption from a coal-bed

We study the desorption of methane from a coal-bed. A model taking into account both methane diffusion in coal - blocks and its filtration through the system of open pores and cracks is developed. Methane pressure in the coal-bed is found for an arbitrary instant of time. Dependency of the rate of methane release upon the block size, open and closed porosity, viscosity, solubility, bed pressure and temperature is established. We derive the effective coefficient of diffusion of methane in blocks containing closed pores filled with gaseous methane. It is shown that at a hindered diffusion methane is distinctly divided into the quick and the slow one. (C) 2007 Elsevier Ltd. All rights reserved.