Theoretical analysis of influencing factors on resistance in the process of gas migration in coal seams

Inspired by previous resistance models for porous media, a resistance expression of gas migration within coal seams based on the ideal matchstick geometry, combined with the Darcy equation and the modified Poiseuille equation is proposed. The resistance to gas migration is generally dynamic because of the variations in adsorption swelling and matrix shrinkage. Due to the limitations of experimental conditions, only a theoretical expression of resistance to gas migration in coal is deduced, and the impacts of tortuosity, effective stress and pore pressure on the resistance are then considered. To validate the proposed expression, previous data from other researchers are adopted for the history matching exercise, and the agreement between the two is good.