Thermal-hydrological-solid coupling model of coal seam gas extraction based on pore-fracture

In order to study the influence of temperature factors on gas extraction by negative pressure drilling, a thermal-fluid-solid coupling model based on pore-fracture dual porous media was established. By means of numerical simulation, the gas extraction characteristics and extraction effect based on gas-solid coupling model without considering temperature factors were compared. The simulation results show that the permeability results obtained by considering the influence of temperature factors are smaller, and the effect of pressure relief is relatively weak. The higher the initial coal seam gas pressure is, the more obvious the coal seam temperature decreases. Considering the influence of temperature change, for different effective extraction radius R, the multi-hole spacing of 2 \sqrt3 R / 3, 2R, 4R, 6R is carried out, and the change rule of effective extraction area is obtained. It is concluded that the effective extraction area develops from multiple small cylinders to a large rounded triangular prism with the increase of extraction time, and finally tends to a regular large cylinder. It is expected to provide some reference value for the design of pre-drainage coal seam gas and the prevention and control of actual gas disasters.