Construction of a coal-bed methane simulator with nitrogen injection capability

Described in this study is a two dimensional, two phase, coalbed methane degasification computer simulator that has been developed. The Implicit Pressure Explicit Saturation (IMPES) method is employed to solve the nonlinear partial differential equations that were derived for the model. The model accounts for stress dependent porosity and permeability, the Klinkenberg slippage effect, and the effect of desorption on porosity and permeability (i.e. shrinkage of the coal matrix due to desorption). A capability to model induced fractures is also included.;After the simulator was validated, a nitrogen injection capability was introduced in which the sorption isotherm was redefined to account for two gases adsorbing on the coal. Without reducing the total gas phase pressure, nitrogen injection into the coal seam, is shown to reduce the methane concentration and consequently enhance the coalbed methane recovery.