1. Faculty of Energy and Safety Engineering,Anhui University of Science and Technology,Huainan　 232001,China; 2. Key Laboratory of Safety and High- efficiency Coal Mining,Ministry of Education, Huainan 　 232001, China; 3. Mine Safety Technology Branch of China Coal Research Institute, Beijing 　100013,China;4. Beijing Tiandi-Marco Electro-Hydraulic Control System Co. ,Ltd. ,China Coal Technology and Engineering Group,Beijing　 100013,Chi-na; 5. Huainan Mining (Group) Co. ,Ltd. ,Huainan　 232001,China

水力压裂是增加煤岩体透气性的有效方法之一,针对深部水力压裂存在的问题,提出了"水-砂-水"(W-S-W)水力压裂强化增透技术,以千米深井高瓦斯煤层为研究背景,开展了W-SW水力压裂强化增透试验和常规水力压裂试验,并对增透效果进行了考察。结果表明:煤体的非均质性和孔隙裂隙分布的非均匀性导致了煤体非对称性增透,在水力压裂的作用下裂缝的扩展演化是递进循环式的,并依次经历了能量缓慢增长、微裂隙萌生、局部损伤破坏、裂缝迅速扩展、裂缝网络循环扩展演化5个阶段。高压水对煤体内部结构产生切割,形成一种高压水驱动裂隙弱面不断扩展、延伸的连锁效应,并使支撑剂(砂)楔入到裂缝端部,抑制了裂缝的闭合,增加了煤体的透气性。采用W-S-W水力压裂强化增透区域煤层的百孔抽采量最高达1.2 m~3/min,平均百孔抽采量与瓦斯体积分数分别为0.77 m~3/min,52%,与常规水力压裂区域的平均百孔抽采量0.44 m~3/min和瓦斯体积分数31%相比分别提高了0.75倍、0.68倍,与未压裂区域的平均百孔抽采量0.32 m~3/min和瓦斯体积分数24%相比分别提高了1.4倍、1.2倍,W-S-W水力压裂强化增透区域煤层的百孔抽采量与瓦斯体积分数均具有明显的峰值阶段,且稳定抽采阶段可持续45 d以上,瓦斯抽采时效性明显,实现了千米深井高瓦斯煤层大范围增透和长时高效抽采瓦斯。

Hydraulic fracturing is one of the effective methods which increases the permeability of coal and rock. The technology of permeability enhancement through hydraulic fracturing by the way of water-sand-water ( W-S-W) was put forward in order to overcome the problems of hydraulic fracturing in deep mining. The experiments of permeability enhancement through upward hydraulic fracturing by the way of W-S-W and conventional hydraulic fracturing were carried out at a high gas coal seam in a deep mine,and the effect of permeability enhancement was investigated. The results show that the heterogeneity of coal and the non-uniformity of the pore and fracture distribution leads to the asymmetric permeability enhancement. The extension and evolution of crack is progressive-circulating under the effect of hydraulic fracturing and experiences five stages in turn including the slow growth of energy,micro-cracks initiation, local damage and destruction,crack rapid expansion,the cyclic extension and evolution of crack network. The internal structure of coal has been cut by high pressure water and a chain effect of weak surface in fracture,which is constantly expanded driven by high pressure water,has been formed. The proppant (sand) is wedged in the ends of cracks and inhibited their closings,which increases the permeability of coal body. The highest gas extraction volume of one hun-dred holes is up to 1. 2 m3 / min in the permeability enhancement area through W-S-W hydraulic fracturing,the average extraction volume and gas volume fraction of one hundred holes is 0. 77 m3 / min and 52% respectively,which is in-creased 0. 75 times and 0. 68 times compared with the average extraction volume (0. 44 m3 / min) and gas volume fraction (31% ) of one hundred holes in the conventional hydraulic fracturing region,and which is increased 1. 4 times and 1. 2 times compared with the average extraction volume (0. 32 m3 / min) and gas volume fraction(24% ) of one hundred holes in the non-fractured region. There are some distinct peak stages of the extraction volume and gas volume fraction of one hundred holes in the permeability enhancement area through W-S-W hydraulic fracturing. The stable extraction stage can continue over 45 days and the timeliness of gas drainage is obvious,the permeability enhancement in a wide range seam and long-term and efficient drainage gas in high-gas coal seam in kilometer deep well is a-chieved.

国家自然科学基金资助项目(51604154)；安徽省高校自然科学研究项目重点资助项目(KJ2017A093)；煤矿安全高效开采省部共建教育部重点实验室开放基金资助项目(JYBSYS2017105)；

Ma Haifeng,Cheng Zhiheng,Zhang Kexue,et al. Intensive permeability enhancement experiment through hydraulic fracturing by way of wa-ter-sand-water in kilometer deep well with high gas seam[J]. Journal of China Coal Society,2017,42(7):1757-1764.