煤矿井下煤层顶板分段加砂压裂增渗技术与应用

    Technology and application of sublevel sand fracturing and permeability enhancement of coal seam roof in underground coal mine

    • 摘要: 为解决碎软煤层水力压裂裂隙易闭合、压裂不均匀、压裂效果差、瓦斯抽采困难等问题,自主研发了定向喷砂射孔装备及工艺技术、水力加砂分段压裂装备及工艺技术,提出煤层顶板定向长钻孔“定向喷砂射孔+分段加砂压裂”增加煤层透气性的思路,并在阳泉矿区新景煤矿3#煤层顶板开展工程试验,形成了煤层顶板定向长钻孔水力加砂分段压裂工艺技术。试验结果表明:成功实现了609 m煤层顶板长钻孔分6段加砂压裂,施工排量超过1 m3/min,单段注液量超过150 m3,累计注液量967 m3;压裂孔底至孔口破裂压力呈逐渐减小,最大破裂压力为29.6 MPa。注入核桃壳砂比例最高达到3%,单段最大注入核桃壳砂2.41 t,累积加入13.11 t。统计分析60 d瓦斯抽采数据,平均抽采瓦斯体积分数60.6%;单日最高瓦斯抽采纯量达到1 381.5 m3,抽采瓦斯体积分数较顺层钻孔和千米钻孔分别提高了8.81倍和3.96倍;百米钻孔抽采纯量分别提高了21.4倍和7.28倍,取得了很好的增透效果。

       

      Abstract: In order to solve the problems of hydraulic fracturing fractures easy to close, uneven fracturing, poor fracturing effect and difficult gas drainage in broken soft coal seam, combinning with the current mature drilling technology, self-developed directional sand blasting perforation equipment and process technology, hydraulic sand fracturing equipment and process technology, the idea of “directional sand blasting perforation + staged sand fracturing” for directional long drilling of coal seam roof to increase coal seam permeability was proposed, and the engineering test has been carried out in Xinjing Coal Mine 3# coal seam roof in Yangquan Mining Area. The hydraulic sand fracturing technology of long directional drilling in coal seam roof is formed. The test results show that the long drilling hole in the roof of 609 m coal seam is divided into 6 sections for sand fracturing, the construction displacement is more than 1 m3/min, the single section liquid injection is more than 150 m3, and the cumulative liquid injection is 967 m3; the fracture pressure from the hole bottom to the orifice decreases gradually, and the maximum fracture pressure is 29.6 MPa. The highest proportion of walnut shell sand injected is 3%, the maximum injection of walnut shell sand in a single section is 2.41 t, and the cumulative addition is 13.11 t. Statistical analysis of 60 d gas drainage data shows that the average gas drainage concentration is 60.6%; the maximum net amount of gas drainage in a single day reaches 1 381.5 m3. The gas drainage concentration is 8.81 times and 3.96 times higher than that of bedding hole and kilometer hole respectively; the net extraction volume of 100 m borehole was increased by 21.4 times and 7.28 times respectively, and a good antireflection effect was obtained.

       

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