Flow of coal-bed methane to a gallery

Coal-seam methane reservoirs have a number of unique feature compared to co nventional porous or fractured gas reservoirs. We propose a simplified math ematical model of methane movement in a coal seam taking into account the f ollowing features: a relatively regular cleat system, adsorptive methane st orage, an extremely slow mechanism of methane release from the coal matrix into cleats and a significant change of permeability due to desorption. Parameters of the model have been combined into a few dimensionless complex es which are estimated to an order of magnitude. The simplicity of the mode l allows us to fully investigate the influence of each parameter on the pro duction characteristics of the coal seam. We show that the reference time o f methane release from the coal matrix into cleats - the parameter which is most poorly investigated - may have a critical influence on the overall me thane production.