Numerical simulation of gas flow process in mining-induced crack network

The exploitation of coal bed methane or coal gas is one of the most effective solutions of the problem of coal gas hazard. A better understanding of gas flow in mining-induced cracks plays an important role in comprehensive development and utilization of coal gas as well as prevention of coal gas hazard. This paper presents a case study of gas flow in mining-induced crack network regarding the situation of low permeability of coal seam. A two-dimensional physical model is constructed on the basis of geological background of mining face No. 1122(1) in coal seam No. 11-2, Zhangji Coal Mine, Huainan Mining Group Corporation. The mining-induced stress and cracks in overburden rocks are obtained by simulating an extraction in physical model. An evolution of mining-induced cracks in the process of advancing of coal mining face is characterized and three typical crack networks are taken from digital photos by means of image analysis. Moreover, the numerical software named COMSOL Multiphysics is employed to simulate the process of gas flow in three representative crack networks. Isograms of gas pressure at various times in mining-induced crack networks are plotted, suggesting a shape and dimension of gas accumulation area.