Study on permeability model of bedding coal and rocks based on equivalent fracture aperture

Abstract

In order to improve the anisotropy characteristics of permeability model in quantitatively describing mechanical deformation and permeability behavior of bedding coal rocks, take the fracture aperture of parallel bedding coal rocks as the benchmark, introduce the equivalent fracture aperture coefficient, and make the fracture aperture of non-parallel bedding coal rocks equivalent, we propose a permeability evolution model of bedding coal and rocks based on equivalent fracture aperture coefficient. The results show that with the increase of the bedding angle, the permeability of bedding coal and rocks decreases significantly, and the larger the bedding angle is, the smaller the dynamic permeability changes with the change of gas pressure; the adsorption effect has a significant impact on the evolution of permeability, but they are in a competitive relationship under different mechanical boundaries. The effect of effective stress on permeability is in a dominant position under the boundary of constant surrounding rock stress, while the adsorption effect is dominant under the fixed displacement boundary condition; for gas drainage of bedding coal and rock, drainage along the bedding direction can greatly improve the drainage efficiency.

Keywords

• gas extraction
• bedded coal and rock
• equivalent fracture aperture
• permeability
• gas-solid coupling