Research progress on analytical models of permeability for coal measure gas reservoir

Permeability is one of the most important parameters for evaluating the feasibility of commercial exploitation of coal measure gas. In order to accurately evaluate the feasibility of commercial exploitation of coal measure gas, based on geometric models of naturally fractured reservoirs, the cubic law of permeability and porosity and the exponential relationship between permeability and effective stress, the research status of analytical models of permeability for coal measure gas reservoirs is investigated and analyzed. The factors affecting permeability are analyzed and the results show that, the dynamic diffusion of gas in the matrix results in unequal matrix pressure and fracture pressure; the anisotropy of permeability is caused by the difference in the opening of surface and end cleats; coal measure gas reservoir is a discontinuous medium and the elastic modulus varies with the change of effective stresses; the effective stress coefficient and fracture compressibility have a significant effect on permeability. According to the analysis, the test method of the elastic modulus, the effective stress coefficient and fracture compressibility is proposed.