EVALUATION OF THE IMPACT OF THE DEGASIFICATION PROCESS ON INFLOW OF METHANE GAS INTO COAL MINES: A NUMERICAL EXERCISE.

In this study a two-phase, two-dimensional finite-difference model was used to predict the methane emission rates into active mine working area under several methane drainage schemes. The numerical model utilizes a recently developed multimechanistic flow theory which describes the flow of methane in an heterogeneous and anisotropic coal seam. Transport of methane in the micropore structure of the coal is described by the Fick's law of diffusion under the influence of existing concentration gradient, while flow in the more permeable butt and face cleats (macropore spaces) is formulated by Darcy's law under the influence of existing pressure gradient. The desorption of the methane is accounted with the aid of a quasi-steady kinetic sorption model. A series of simulation studies were conducted in a systematic manner by sifting through the parameters associated with the coal seam characteristics and the degasification strategies in order to understand those which most significantly affect the methane emission rates in the face areas during mining.