高瓦斯煤层注液态CO_2压裂增透技术试验研究

Experimental Research on Fracturing Antireflection Technology of Liquid CO_2 in High Gas Coal Seam

基于液态CO_2的低温冻结及相变增压特性能够有效致裂煤体,可以达到煤层增透的目的。在淮南矿区张集北矿17246工作面开展了煤层注液态CO_2压裂增透技术工业性试验,沿工作面走向布置2个压裂钻孔、12个抽采钻孔,分2个阶段进行压裂试验,压注液态CO_2共计4.0 t。对Y1、Y2压裂钻孔的压力、流量及泵压进行在线监测,实测压裂后连续26 d瓦斯抽采效果。研究结果表明:试验过程中压裂液流量随压力升高呈现波动特性,试验工艺系统稳定;抽采支管的瓦斯纯流量是压裂前的2.1～3.2倍,瓦斯浓度是压裂前的1.6～3.1倍,累计26 d的瓦斯抽采总量为32 288.57 m3,与普通密置钻孔抽采瓦斯技术相比,经液态CO_2压裂后煤层瓦斯抽采效率明显提高。

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.