中硬低渗煤层定向长钻孔水力压裂瓦斯高效抽采技术与应用

Technology and application of high efficiency gas extraction by directional long borehole hydraulic fracturing in coal seams of medium hardness and low permeability

  • 摘要: 针对黄陇侏罗纪煤田中硬煤层渗透性差、瓦斯抽采浓度及流量衰减速度快等问题,利用自主研发的水力压裂成套工艺设备,提出煤层定向长钻孔水力压裂瓦斯高效抽采技术,并在黄陇煤田黄陵二号煤矿进行工程应用试验。现场共完成5个定向长钻孔钻探施工,单孔孔深240~285 m,总进尺1 320 m;采用整体压裂工艺对5个本煤层钻孔进行压裂施工,累计压裂液用量1 557.5 m3,单孔最大泵注压力19 MPa;压裂后单孔瓦斯抽采浓度及百米抽采纯量分别提升0.7~20.5倍、1.7~9.8倍;相比于普通钻孔,压裂孔瓦斯初始涌出强度提升2.1倍,钻孔瓦斯流量衰减系数降低39.6%。试验结果表明:采取水力压裂增透措施后,瓦斯抽采效果得到显著提升,煤层瓦斯可抽采性增加,为类似矿区低渗煤层瓦斯高效抽采提供了技术支撑。

     

    Abstract: Aiming at the problems such as poor permeability of coal seams and fast attenuation of gas extraction concentration and flow rate in Jurassic coalfield of Huanglong, the complete set of independently developed hydraulic fracturing equipment was used, the high-efficiency gas extraction technology of directional long borehole hydraulic fracturing of coal seams was put forward, the engineering application test was carried out in Huangling No.2 coal mine in Huanglong coalfield. Five directional long boreholes were drilled. The depth of single borehole was 240~285 m and the total footage was of 1 320 m. The integrated fracturing process was used to fracture coal seams in five boreholes. The cumulative amount of fracturing fluid was 1 557.5 m3, and the maximum pumping pressure for the single borehole was 19MPa. After fracturing, the gas extraction concentration and the drainage quantity per 100 m were increased by 0.7-20.5 times and 1.7-9.8 times respectively. Compared with ordinary boreholes, the initial gas-gushing strength of the fractured borehole was increased by 2.1 times, and the attenuation coefficient of gas flow of the boreholes was reduced by 39.6%. The test results show that the gas extraction effect can be significantly improved and the coal seam drainage ability can be increased after adopting the permeability improvement measures of hydraulic fracturing, providing technical support for the high-efficiency gas extraction of low-permeability coal seam in similar mining areas.

     

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