Coal permeability evolution and gas production performance prediction under the coupling action of stress-residual water-pulverised coal

Under the influence of hydraulic fracturing and drainage, coalbed methane wells will produce a large amount of pulverised coal and residual water. Stress, residual water and coal dust is well known to affect the permeability during coalbed methane mining. Most studies consider the three effects separately, which is inconsistent with the actual situation. Therefore, a dynamic evolution model of permeability based on the coupling effect of stress-residual water-pulverised coal is constructed in this paper. Numerical analysis is carried out using a commercial finite element method (FEM) software (COMSOL Multiphysics 5.6), and the model is verified by combining with field mining data. Results indicate that the gas production in the stimulated reservoir volume (SRV) is higher than that in the unstimulated reservoir volume (USRV) due to the influence of hydraulic fracturing and permeability enhancement. However, after 820 days, under the influence of the gas source, the gas production of the USRV is the same as that of the SRV. [Received: July 12, 2022; Accepted: May 10, 2023]