层状巨厚煤层水力压裂瓦斯抽采技术应用研究

Research on Application of Hydraulic Fracturing Gas Extraction Technology in Thick Layered Coal Seam

为解决层状构造煤层顺层定向钻孔瓦斯抽采效率低的问题,通过对榆树田煤矿煤层地质条件进行分析,对压裂裂隙发育情况进行数值模拟,得出水力压裂主裂隙沿平行最大主应力方向、垂直水平最小主应力方向发育,破裂形式主要为拉张破裂;分别将110501工作面第1循环和第2循环水力压裂定向钻孔层位设计在煤厚1/2处和半暗型煤分层中,通过对比可知第2循环钻孔压裂效果好于第1循环,平均瓦斯体积分数和月平均纯瓦斯流量分别是第1循环相应参数的4倍和3倍。研究结果表明:针对特定层状构造煤体,压裂钻孔的设计层位会对整体煤层压裂和瓦斯抽采造成严重影响。

In order to solve the problem of low efficiency of gas extraction by along-layer directional drilling in layered structure coal seam,through the analysis of coal seam geological conditions in Yushutian coal mine and the numerical simulation of fracturing fracture development,it was reached that the hydraulic fracture develops along the parallel direction of maximum principal stress and vertical direction of minimum principal stress,and the fracture form is mainly tensile fracture.The first and second hydraulic fracturing directional boreholes in 110501 working face were designed at the coal thickness of 1/2 and in the substratum of semi-dark briquemite.Through comparison,it can be seen that the fracturing effect of drilling in the second cycle is better than that in the first cycle,and the average gas volume fraction and monthly average pure gas flow rate are 4 and 3 times of corresponding parameters in the first cycle respectively.The results show that the design of the fracturing borehole has an serious influence on the fracturing and gas extraction of the whole coal seam.