彬长矿区中硬煤层长钻孔分段水力压裂瓦斯抽采技术

Gas extraction technology with long borehole segmented hydraulic fracturing in medium-hard coal seam of Binchang mining area

针对中硬煤层水力压裂区域超前抽采压裂施工过程中存在的工期长、孔内事故率高、风险大、经济性差等问题,以彬长矿区4号煤层为研究对象,采用试验分析、数值模拟和系统优化等方法,研究出4号煤层分段压裂合理泵注压力、排量以及新型节流器,采用改进后压裂工艺在大佛寺煤矿完成了3个长度500 m以上钻孔的分段水力压裂施工,累计压裂段数23段,泵注压力为7.56~9.70 MPa,排量为18.63~22.11 m3/h,均未出现孔内事故。改进后,单孔水力压裂工期由12 d减少至7~8 d,压裂钻孔初始瓦斯抽采量是常规方式的1.29和1.38倍,瓦斯抽采量衰减系数是常规方式的9.1%和6.8%,压裂钻孔抽采效果得到大幅提升。

Aiming at the problems in the construction process of long borehole segmented hydraulic fracturing in the medium-hard coal seam,such as long construction period,high accident rate,high risk,and poor economy,the No.4 coal seam in the Binchang mining area was taken as the research object,and the methods of experimental analysis,numerical simulation and system process optimization were used to study the new restrictor suitable for segmented fracturing in No.4 coal seam,as well as the reasonable pump pressure.The improved fracturing technology was used to complete the hydraulic fracturing construction of 3 boreholes over 500 m with a total of 23 sections.The range of pumping pressure is 7.56~9.70 MPa with discharge volumes of 18.63~22.11 m 3/h,and all without accidents in the borehole.After the improvement,the duration of single hole hydraulic fracturing was shortened from 12 days to 7~8 days,the initial gas extraction volume of fracturing borehole is 1.29 and 1.38 times that of conventional mode,and the attenuation coefficient of gas extraction volume was reduced to 9.1%and 6.8%of conventional mode.The gas extraction effect of fracturing borehole was greatly improved.The research results provide a new technical way for high-efficiency gas extraction in long directional drilling areas of the medium-hard coal seams.