采动影响下邻空定向钻孔整体水力压裂瓦斯抽采技术

Integral hydraulic fracturing gas drainage technology for directional drilling in gob-side entry under influence of mining

针对采动影响下邻空定向钻孔所面临的顺煤层成孔难度大,常规措施无法实施水力压裂的难题,以黄陵二号煤矿2号煤层邻空水力压裂钻孔为研究对象,提出了“先入顶板后进煤层”钻孔布置思路,以及开孔点与见煤点距离的综合确定方法,得出开孔点与见煤点距离的最小值为71.6 m;并确定了配套的封隔器类型和孔内压裂工具组合。在209工作面回采影响区域开展了工程实践,成功实施3个“先入顶板后进煤层”钻孔的定向钻进和整体水力压裂施工:定向钻孔长度240~270 m,岩孔段开孔点与见煤点距离为105~117 m,单孔压裂段长度126~165 m,泵注压力15.2~19.0 MPa,压裂液用量248~315 m^(3)。实测水力压裂影响半径达36~54 m,压裂钻孔平均瓦斯抽采体积分数与瓦斯抽采量较压裂前提升了4~16倍和3~8倍,压裂区域内瓦斯预抽钻孔百米瓦斯抽采量是未压裂区域的2倍,且抽采体积分数大于60%的钻孔数量是未压裂区域的5.1倍。

For the difficulties in the construction of the directional drlling along the coal seam adjacent to the goaf under the influence of mining,such as the difficulty in hole formation and the inability of conventional measures to implement hydraulic fracturing,this paper takes the hydraulic fracturing drlling in the goaf adjacent to the 2 coal seam of Huangling No.2 Coal Mine as the research object,and puts forward the dilling layout idea of"entering the roof before entering the coal seam"The comprehensive determination method of main key parameters is obtained,and the minimum value of opening point to coal point(L value)is 71.6 m;the stepwise release packer and matching in-hole fracturing tool combination suitable for the integral hydraulic fracturing of directional drlling are determined.The engineering practice has been carried out in the affected area of mining in the 209 working face,and the directional drilling and overall hydraulic fracturing construction of three"first entering the roof and then entering the coal seam"boreholes have been successfully implemented.The directional drilling length is 240-270 m,the rock hole section(L value)is 105-117 m,the single-hole fracturing section length is 126-165 m,the pumping pressure is 15.2-19.0 MPa,and the fracturing fluid consumption is 248-315 m^(3).The measured influence radius of hydraulic fracturing is 36-54 m.The average gas drainage concentration and volume of fracturing boreholes has increased by 4-16 times and 3-8 times compared with that before fracturing.The gas drainage volume of pre-pumping boreholes in the fracturing area is twice that of the unfractured site,and the number of boreholes with gas drainage concentration greater than 60%is 5.1 times that of the unfractured area.