Numerical simulation of coal-bed methane displacement by underground gas injection based on multi-physics coupling

A multi-physics coupling mathematic model,which includes seepage,diffusion and multi-gas adsorption-desorption,was proposed. Based on software of COMSOL Multiphysics,methane quantity in releasing holes and degassing holes was simulated under nitrogen or carbon dioxide injection in coalbed. The results show that under the condition of injection pressure 0. 5 MPa and injection-drainage hole spacing 0. 15 m,releasing hole natural emission pure...