Research on hydraulic slitting anti-reflection technologyfor borehole drilled along broken soft coal seam

In order to solve the problem of poor gas permeability, long gas extraction time and difficulty in extraction, the high pressure hydraulic slitting technology was applied to the gas drainage of the sand hole in broken soft outburst-prone coal seam. Hydraulic cutting test was carried out in No.4 coal seam of Aiweiergou mining area in Xinjiang, and seven high pressure hydraulic slit drilling holes and seven ordinary extraction drilling holes were constructed. The cutting pressure and the cutting radius were investigated, and the gas drainage was compared. The research shows that the cutting pressure of No. 4 coal seam is about 55 MPa. The slit is cut at a pressure of 55 MPa for five minutes, and the slot radius is about 0.89 m; the downhole drilling is not suitable for high-pressure hydraulic slitting. Compared with the extraction effect of ordinary extraction holes, the hydraulic drilling hole can increase the single hole concentration, single hole flow rate and extraction purity by at least two times. The drainage effect of the first 22 days of hydraulic slotted drilling is obviously better than that of ordinary extraction holes, but the attenuation speed is very fast. After about 30 days, the effect of the two extractions is basically close.