Optimization and Experimental Study of Underground Hydraulic Fracturing Method in Low Permeability and High Gas Coal Seam

Abstract

With mine mining depth increasing, the situation of mine gas control is more rigorous, and the existing single hydraulic fracturing method often cannot achieve the ideal effect. Based on the characteristics of high gas and low permeability coal seam, this paper designed different ways of hydraulic fracturing experiment to investigate the differences of gas extraction ability, and eventually optimize the hydraulic fracturing method. The experimental results show that repeated hydraulic fracturing and directional hydraulic fracturing methods are more suitable for increasing soft coal seam permeability than conventional hydraulic fracturing method, and the gas extraction ability of repeated hydraulic fracturing is better than directional hydraulic fracturing. After repeated hydraulic fracturing, the single-hole average pure volume of gas drainage has reached 10.224m³/d, which is 2.5 times as much as the conventional hydraulic fracturing; The extraction concentration is 63% -72%, with an average of 67.8%, which is 19.2% higher than the conventional hydraulic fracturing.