Direct and inverse problems of gas emission and the sorptive deformation of coal beds

Using equations of state for fractured-porous media to describe the sorption-induced deformation of coal, we develop a geomechanical model for radial gas influx to a borehole drilled in a coal bed with the concurrent evolution of the stress field in the borehole environment. A numerical and analytical method is put forward for solving the corresponding system of equations for poroelastic media. The correlation is found between the volume of slack withdrawn from the borehole (when opening up gas-bearing seams), the sorption-and-storage capacities of coal, the permeability $k$, and the natural horizontal stress $\sigma_h$. The solvability is shown of the inverse boundary-coefficient problem on $k$ and $\sigma_h$ from the shut-in well pressure. The express-method for estimating the permeability from pressure measurements taken in a borehole operating in pressure drop mode is justified.