Research on reasonable hole spacing of bedding drilling under the influence of superposition effect

In order to determine the optimum hole spacing for gas extraction borehole,a gas-solid coupling mathematical model considering the evolution of coal permeability,solid mechanics and gas diffusion-seepage was established based on the assumption of pore-fracture dual media. Taking the N2206 working face of Yuwu Coal Mine in Shanxi Province as the research object,the numerical simulation study of gas extraction in single borehole and multi-borehole was carried out,and it was found that the effective extraction radius and the extraction time changed as a power exponential function,and the average error between the numerical simulation results and the field test results was 4. 69%. Based on the model validation, the influence of hole spacing on the superposition effect was analysed according to the principle of superposition effect in multi-well gas extraction, and a mathematical model of hole spacing in multi-well gas extraction was established based on effective extraction radius and the influence radius of a single well. It was found that the optimal hole spacing of N2206 working face was 9. 2 m. Field testing has confirmed the accuracy of the formula correlating hole spacing with the effective extraction radius and influence radius of a single hole.