Optimization Study and Validation of Gas Extraction Parameters Based on Heat-Fluid-Solid Coupling in Coal Seam

In order to optimize the arrangement parameters of gas extraction in the downhole layer, the transport level of gas-containing coal was studied through industrial tests and low-temperature liquid nitrogen tests, and the heat-fluid-solid coupling model of the coal-rock deformation field, gas seepage and diffusion field, and temperature field was established, and numerically solved by using COMSOL. The optimal borehole diameter was determined by the single-hole gas extraction capacity, effective radius and extraction impact radius, based on which the superimposed extraction mechanism of neighboring boreholes and the change of gas extraction capacity under multi-hole extraction were studied, and the spacing of boreholes was finally determined. The study shows that: the test coal samples have high adsorption level of gas, the pressure difference between matrix and fissure under the influence of Klinkenberg effect leads to the decrease of gas seepage rate and extraction to a fixed value, the decreasing trend of coal body temperature decreases with the increase of extraction time, the decreasing rate of coal body permeability rises with the increase of attenuation coefficient, and the decreasing rate of gas extraction is accelerated accordingly. The reasonable drill hole diameter of 172403 working face in Dashucun Mine is 114mm, and the spacing of the holes is 6m, which has a good effect of on-site extraction and ensures the safe production of the mine and the sustainable development of the resources.