Combined Effects of Stress, Gas Adsorption, and Temperature on the Evolution of Coal Seam Permeability and Slippage Effect.

The complexity of the evolution of the permeability of coal is determined by the reservoir structure. Further, there exists an interaction between the fracture matrix, which further complicates changes in permeability. When the actual mining conditions of a coal mine are considered, a permeability model that considered the combined effects of stress, gas adsorption, and temperature was proposed. Subsequently, the model is verified by published test data. Based on the analysis of permeability, a calculation model of the slip coefficient that considered the combined effects of stress, gas adsorption, and temperature is proposed. With respect to this, any change in the slippage coefficient is only determined by the width of the fracture channel, which affected the flow of coal gas. In the process of a temperature increase, the slip coefficient tends to increase and the larger effective stress corresponds to a larger slip coefficient. In addition, under constant-temperature conditions, we also discuss the evolution of coal permeability and the variation of the coal gas slippage factor under different boundary conditions through the proposed model. This study aims to further the understanding of the seepage characteristics and slippage effects of coalbed methane, which would have a positive impact on the mining of coal.