On the mechanism of gas release from a coal bed into a fluid fracturing crack (Q2771581)

Diffusion of methane into a fluid fracturing crack in loaded coal bed is described by one-dimensional diffusion equation under proper initial and boundary conditions. The unknown function is methane concentration in coal. An exact closed-form solution of the boundary-value problem is found and analyzed. Comparison with experimental data shows, that the mechanism of diffusion without forming additional surfaces is incapable to ensure observed speeds of outgassing from a coal bed of fluid fracturing. A dimensionless criterion of coal capacity to degasification, that takes into account the coal capacity to shrinkage, filtrational and diffusive characteristics, fractal nature of the surface of voids, geometric parameters and time of degasification, is suggested.