A Mechanical Model and Numerical Method for Gas Seepage Analysis Considering Gas Desorption in Heterogeneous Coal.

The primary purpose of this paper is to research the law of gas seepage considering gas desorption in heterogeneous coal theoretically. A mechanical model on gas seepage considering gas desorption in heterogeneous coal is established, and the governing equation of gas seepage is discretized by the finite volume method with a new meshing strategy. Moreover, the gas state distribution and change in coal with different heterogeneity are calculated. The numerical results show that the effects of coal heterogeneity on gas seepage and desorption are significant. The coal with high heterogeneity is not accessible for gas to seep in it, resulting in a great gas pressure gradient, which is necessary for an outburst initiation. Additionally, the gas pressure gradient in the coal with high heterogeneity decreases more slowly than that with low heterogeneity. Hence, the possibility of outburst initiation is greater, and the outburst duration may be longer if the coal has high heterogeneity. Due to the strong randomness of the distribution and change of gas velocity in heterogeneous coal, the coal and gas outbursts in the field may be far more complex than that induced in the laboratory by using briquette, which is close to a homogeneous porous medium. [ABSTRACT FROM AUTHOR]