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坚硬顶板定向长钻孔水力压裂卸压瓦斯抽采研究

Pressure relief gas drainage by directional drilling hydraulic fracturing in hard roof

  • 摘要: 为了解决焦坪矿区特厚煤层坚硬顶板综放工作面瓦斯防治难题,通过顶板定向长钻孔分段水力压裂技术,以陕西崔家沟能源有限公司2305综放工作面为对象进行工程应用研究。现场施工定向长钻孔3个,最大单孔长度602 m。采用倒退式分段压裂工艺对3个定向长钻孔进行水力压裂,累计注液量983.1 m3,总压裂时间5 231 min,单段最大峰值压力37.5 MPa。试验结果表明:经过顶板定向长钻孔水力压裂,工作面初次来压步距缩短29.37%,定向长钻孔平均抽采甲烷体积分数及纯量分别提高了1.92倍和1.57倍,本煤层区域预抽甲烷体积分数及纯量分别提升了1.79倍和2.01倍,初采初放阶段绝对瓦斯涌出量降低19.9%。顶板定向长钻孔分段水力压裂技术通过高压水精准预裂,降低坚硬顶板完整性,增加顶煤及围岩裂隙发育程度,拓展瓦斯运移通道,提高卸压瓦斯抽采效果,研究成果可为焦坪矿区类似地质条件下瓦斯治理提供技术参考。

     

    Abstract: Aiming at the difficult problems of gas prevention and control in hard roof fully mechanized caving face of extra thick coal seam in Jiaoping mining area, the roof directional long borehole staged hydraulic fracturing technology was proposed, and the 2305 fully mechanized caving face of Shaanxi Cuijiagou Energy Co., Ltd. was taken as the object for engineering application research. Three directional long boreholes were drilled on site, with the maximum single hole length of 602 m. Three directional long boreholes were hydraulically fractured by backward staged fracturing technology. The cumulative injection volume was 983.1 m3, the total fracturing time was 5 231 min, and the maximum peak pressure of single section was 37.5 MPa. The results show that, after hydraulic fracturing of the roof directional long borehole, the first weighting step of working face is shortened by 29.37%, the average concentration and purity of directional long borehole gas drainage are increased by 1.92 times and 1.57 times respectively, the concentration and purity of pre-drainage gas in this coal seam area are increased by 1.79 times and 2.01 times respectively, and the absolute gas emission is reduced by 19.9% in the initial mining and initial discharge stage. Roof directional long borehole staged hydraulic fracturing technology reduces the integrity of hard roof, increases the development degree of top coal and surrounding rock fractures, broadens the gas migration channel, and improves the effect of pressure relief gas drainage through accurate pre-splitting of high pressure water, and provides technical support for gas control in Jiaoping mining area under similar geological conditions.

     

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