Seepage-stress coupled model of heterogeneous coal seams based on double-media model

To simulate the cleats´ effects of coalbed on gas flow, coalbed is considered as double-media composed of rock matrix and cleats. With Weilbull distribution the heterogeneity of young´s modulus and strength of rock matrix are simulated, and the cleats (fractured media) are simulated with Desai thin elements. Based on elastic-plastic mechanical theory, gas flow theory and double-media model the seepage-stress coupling mathematical model of heterogeneous coalbed is presented, and the numerical code is developed. The effect of different distance of single cleat from gas production well on gas flow is studied. Results show that cleats could accelerate gas production. Especially, the recovery of coalbed methane would markedly be improved when gas production well just exists in cleat. So some techniques such as hydraulic cutting seam could enhance gas production. Besides, the model is suitable for simulating the effect of heterogeneous coalbed on gas flow, and a new method of simulating gas flow process is provided.