韩城矿区碎软煤层顶板梳状孔水力压裂瓦斯抽采工程实践

韩城矿区碎软煤层发育，煤层透气性差，本煤层钻孔钻进困难，瓦斯抽采效果差。顶板梳状孔水力压裂技术结合了水力压裂技术和定向钻进技术二者的优势，是解决碎软低渗煤层瓦斯抽采难题的有效技术途径。在韩城矿区王峰煤矿3号煤层顶板粉砂岩中施工长钻孔并向煤层开分支，采用套管+封隔器座封的整体压裂方式进行水力压裂工程试验。钻孔总长度344 m，有效压裂长度284 m，累计注水量874.79 m3，最大泵注压力9.4 MPa。试验结束后对钻孔瓦斯抽采相关参数连续监测86 d，钻孔瓦斯抽采体积分数27%~51%，平均42.11%，钻孔瓦斯抽采纯量8.25~21.41 m3/min，平均17.02 m3/min，钻孔累计抽采瓦斯量约210万m3。与常规的穿层钻孔水力冲孔技术相比，该技术百米钻孔瓦斯抽采量提高了11.48倍，初步证明了该技术在碎软煤层瓦斯强化抽采领域的适用性。 

Practice of gas drainage by hydraulic fracturing of roof pectination boreholes in broken soft coal seam in Hancheng mining area

Broken soft coal seams with poor permeability develop in Hancheng mining area, drilling in the coal seams is difficult, the effect of gas extraction is poor. The hydraulic fracturing technology of pectination boreholes in roof combines the advantages of the two technologies of hydraulic fracturing and directional drilling, it is an effective technical way to solve the problem of gas drainage in broken soft coal seams of low permeability. In Wangfeng coal mine, a long borehole was drilled in the roof siltstone of No. 3 coal seam, and had a branches in coal seams, casing and packer seal were used, hydraulic fracturing engineering test was carried out in the way of integral fracturing. The total length of the borehole was 344 m, the effective fracturing length was 284 m, the accumulative water injection was 874.79 m3, and the maximum pump pressure was 9.4 MPa. After the test, the relevant parameters of borehole gas drainage were continuously monitored for 86 days, the concentration of gas drainage was 27%-51%, 42.11% on average, the pure amount of gas drainage was 8.25-21.41 m3/min, 17.02 m3/min on average, the total amount of gas drainage was about 210×104 m3 by roof long boreholes. Compared with conventional hydraulic punching technology, of gas drainage of 100 meter borehole through this technology increased by 11.48 times, it preliminarily proves the applicability of the technology in the field of enhanced gas drainage in broken soft coal seam.