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When coalbed methane is recovered, complex interactions of stress and chemistry have a strong influence on the properties of the coal. These include influences on gas desorption and flow, coal deformation, porosity change and permeability modification. Although coal-gas interactions have been comprehensively investigated, all of these prior studies usually assume that these interactions are under conditions of invariant total stress where effective stresses scale inversely with applied pore pressures.

Here we develop a novel coal permeability model that defines the relations between directional permeabilities and strains, and implement a FE model that couples desorption of the coalbed methane and water flow within a deformable medium (coal) where the effects of deformation are rigorously accommodated. This relaxes the prior assumption that total stresses remain constant and allows exploration of …