Study on the Influence Law of Underground Hydraulic Fracturing on Gas Content of Deep and Low Permeability Coal Seam

Hydraulic fracturing is one of the main methods to solve the difficulty of gas extraction in deep and low permeability coal seam. In order to further improve the gas extraction efficiency and evaluate the fracturing effect objectively, it is necessary to study the influence rule of gas content in coal seam after fracturing. The permeability enhanced test of hydraulic fracturing through drilling in bed plate tunnel was carried out in the deep low permeability coal seam of No.12 Coal Mine in Pingdingshan Coal Mining Group Corporation. 18 boreholes were designed to investigate the effect of fracturing, and the gas content of each borehole was measured by sampling. By sampling and measuring the gas content of each borehole, the variation rule of gas content of the target coal seam and the adjacent coal seam after hydraulic fracturing was analyzed in detail. The results show that the gas content of the target coal seam within the range of 35 m around the fracture hole is 63% lower than the original gas content on average, the gas content of the adjacent coal seam is 27% lower than that of the original coal seam on average; the average decrease of gas content along the inclination of the target coal seam is higher than the trend. The research results provide a reference for the optimization design of hydraulic fracturing drilling and extraction drilling in deep and low permeability coal seam.