Experimental Research on Fracturing Antireflection Technology of Liquid CO₂ in High Gas Coal Seam

Based on the characteristics of phase change supercharging and cryogenic freezing of liquid CO₂ can effectively crack coal and achieve the goal of antireflection.In Huainan mining area,industrial test of fracturing antireflection by liquid CO₂ in coal seam was carried out in 17246 working face of Zhangjibei Coal Mine.Two fracturing boreholes and 12 extraction boreholes were arranged along the working face,and fracturing tests were conducted in two stages,the total weight of liquid CO₂ was 4.0 tons. The pressure,flow rate and pump pressure of fractured boreholes Y₁ and Y₂ were monitored online,the effect of gas extraction for 26 days after fracturing was observed.The results show that the flow rate of fracturing fluid fluctuates with the increase of pressure during the test,and the test process system is stable.The net gas flow rate of the drainage tube is 2.1 to 3.2 times of that before fracturing,and the gas concentration is 1.6 to 3.1 times of that before fracturing.The cumulative total of gas extraction for 26 days is 32 288.57 m³,compared with conventional gas extraction technology with tight borehole,the gas extraction efficiency of coal seam after fracturing by liquid CO₂ is obviously improved.