穿层孔吞吐压裂水力强化抽采技术研究及应用

Research and application of gas drainage with hydraulic reinforcement of water stimulation fracture in borehole through strata

为了解决低透气性煤层高效抽采的难题,采用穿层孔吞吐压裂水力强化改善煤层透气性。分析了水力强化工艺穿层孔瓦斯运移产出过程,研究了水力强化对硬煤储层和软煤层中瓦斯渗透率的影响,分析了水力强化对煤体渗透率的作用及增透机理,并进行了现场效果应用。结果表明：穿层孔吞吐压裂技术提高了煤层透气性,形成瓦斯产出通道,在硬煤中水力强化可在顶底板形成＂虚拟储层＂,瓦斯以渗流为主,软煤中以扩散运移为主;吞吐压裂水力强化通过形成洞穴和裂隙,增加煤层渗透性,减少瓦斯抽采流量衰减系数,提高瓦斯抽采效率。现场实施吞吐压裂水力措施后抽采纯量由14.8 m^3增加至31.9~42.8 m^3;抽采体积分数由14.1%增加至73.9%~77.5%,该技术具有较高的实际推广应用价值。

In order to solve the problem of how to efficiently extract the coal seam with low permeability, the hydraulic measures of stimulation fracturing through strata borehole has been adopted to improve the permeability of coal seam. The gas migration process through borehole in the hydraulic enhanced technology has been analyzed. The effect of hydraulic reinforcement measures on hard and soft coal seam permeability has been studied, and the effect and mechanism of hydraulic reinforcement on the permeability of coal mass has been analyzed, and finally, the field experiment of hydraulic fracturing has been carried out. Research results show that the hydraulic measures of stimulation fracturing through strata borehole technology can improve the permeability of coal seam and contribute to form gas flow channel. There is ＂virtual reservoir＂ in roof and floor in hard coal seam and the gas shows seepage mainly, while, in soft coal seam gas shows diffusion migration mainly. The hydraulic measures of stimulation fracturing can increase the permeability of coal seam through formation of cave and cracks in it, release ground stress and reduce gas flow attenuation coefficient, and consequently improve efficiency of the gas drainage. By using hydraulic fracturing measures in coal seam the pure quantity of gas drainage increases from 14.8 m^3 to 31.9-42.8 m^3; the gas concentration increases from 14.1% to 73.9%-77.5%. This technology has very wide popularization and application prospects.