Investigation of gas enhanced extraction technology by hydraulic fracturing of comb hole in the coal seam roof of Sangshuping No.2 well

It is difficult to drill holes in the coal seam of Sangshuping No.2 well.The permeability of the coal seam is poor, the concentration of gas extraction is low, and the flow rate is small.In order to improve the effect of mine gas prevention and control, comb-shaped long drilling and hydraulic fracturing are carried out in the roof sandstone of No.3 coal seam in the north area of Sangshuping No.2 well, and the technical means of mine gas prevention and control are explored.One drilling hole is completed by using forward branch hole technology.The length of the main hole is 588 m, and eight branch holes are constructed with a total footage of 1 188 m.Among them, the coal seam is 227 m, the rock seam is 961 m, and the distance between the main hole and the top of the coal seam is 0-3.28 m.Hydraulic fracturing is carried out in four stages, with cumulative water injection of 2 012 m³ and maximum pump injection pressure of 8.74 MPa.Within three months after completion of the construction, the average daily gas extraction purity of drilling holes is about 1 500 m³.The gas extraction purity of 100-meter drilling holes in fracturing holes is 1.2 times that of hydraulic slotting holes and 4.0 times that of conventional drilling holes.The applicability of roof comb-shaped long borehole hydraulic fracturing technology in the field of coal mine gas prevention and control is preliminarily proved.