~定向长钻孔水力压裂综合了定向钻孔高效抽采技术和水力压裂增透强化抽采技术优势，能够有效提高瓦斯治理效率、扩大瓦斯治理规模，具有引领国内外低渗煤层瓦斯高效治理技术研究开发与应用的趋势。针对韩城王峰煤矿3号煤层地质条件，将理论分析、数值模拟、工业性试验等方法结合使用，系统分析了顶板水力压裂裂缝扩展演化特征，得出了压裂孔直径和压裂压力对裂缝发育的影响规律，进行了煤层顶板水力压裂方案设计，并在3号煤层顶板开展了工程实践，主要研究成果如下:
(1)原始地应力和顶板的力学性质影响裂缝起裂，当高压水注入钻孔后，裂缝整体会沿着最大主应力的方向进行发育，最大主应力方向上裂缝扩展的增长速度与压裂压力基本成正相关。
(2)随着压裂压力的增大，裂缝扩展呈现出如下规律压裂压力为5~8MPa时，裂缝首先在水平方向产生，垂直方向上均未产生裂隙;压裂压力大于10MPa时，随着压裂压力的增大，裂缝在竖直方向逐渐延伸，且裂缝宽度沿水平方向逐渐扩展;相同压裂压力下，压裂孔孔径越大，塑性区扩展长度越大，裂缝扩展越大;当压裂压力大于10MPa后，垂直方向上的裂缝扩展速率大于水平方向，裂缝沿最大主应力方向扩展速度最快。
(3)结合压裂钻孔瓦斯抽采效果可知，泵注压力曲线整体呈“锯齿状”上下波动，清水压入岩层天然孔隙后产生微裂隙的“起裂-扩展延伸”行为，局部泵注压力的明显下降表明在微裂隙的基础上地层产生了较大裂隙，即泵注压力曲线整体呈“锯齿状”上下波动、并伴随多次的泵注压力明显下降，为碎软低渗煤层顶板钻孔水力压裂的典型压力曲线，表明水力压裂方案具有科学性及合理性。
(4)采取顶板水力致裂工艺后，在大流量、高压力水动力条件下，有效地降低了煤层的储存压力，煤层上覆岩层发生起裂、扩展、延伸，随着压裂的持续进行，所形成的人工裂隙与天然裂隙以及煤岩结合部的弱面有效贯通，裂隙网络与外界自由面的有效沟通，提高了煤岩体的渗透率，为瓦斯运移流动提供了良好的通道，煤岩体得以卸压和增透，打破煤层原始应力和瓦斯赋存状态，瓦斯在 3 个月内连续解吸，表明了王峰煤矿顶板定向水力压裂取得了理想效果，方案具有可行性及推广性。

~Aiming at the geological conditions lor='red'>of the 3# coal in Hancheng Wangfeng Coal Mine, thetheoretical analysis, numerical simulation, industrial test and other methods are combined tosystematically analyze the evolution characteristics lor='red'>of rolor='red'>of hydraulic fracturing fracture propagation, focusing on the fracture hole diameter and fracturing pressure. The hydraulic fracturing scheme design for the rolor='red'>oflor='red'>of coal seam has been carried out on the influence law lor='red'>offracture development, and engineering practice has been carried out on the rolor='red'>of lor='red'>of coal seam 3#. The main research results are as follows:
(l) The most important factors for crack initiation are the magnitude and orientation lor='red'>ofthe three principal stresses, namely the original ground stress and the physical and mechanical properties lor='red'>of the rolor='red'>of. After high-pressure water is injected into the borehole, the direction lor='red'>ofthe cracksis along the direction lor='red'>of the maximum principal stress.
(2) With the increase lor='red'>of the fracturing pressure, the crack propagation presents thefollowing laws: when the fracturing pressure is 5-8MPa the fractures are first generated in the horizontal direction, and no cracks are generated in the vertical direction; when the fracturing pressure is greater than 10MPa, the fractures With the increase lor='red'>of fracturing pressure, the fracture gradually extends in the vertical direction, and the width lor='red'>of the fracture gradully expands in the horizontal direction; under the same fracturing pressure, the larger the aperture lor='red'>of the fracturing hole, the greater the extension length lor='red'>of the plastic zone, and the greater the extension lor='red'>of the fracture; When the fracture pressure is greater than 10 MPa, the crack growth rate in the vertical direction is greater than that in the horizontal direction, and the crack growth rateisthe fastestin the direction lor='red'>of the maximum princial stress.
(3) Combining with the gas drainage effect lor='red'>of fracturing boreholes, it can be seen that the pumping pressure curve fluctuates up and down in a "saw-tooth shape" as a whole. After clear water is pressed into the natural pores lor='red'>of the rock formation, the behavior lor='red'>of "cracking-expansion and extension" lor='red'>of micro-fractures is generated, and the local pumping pressure is obvious. The decrease indicates that the formation has large cracks on the basis lor='red'>of micro-fractures, that is the pumping pressure curve fluctuates up and down ina "sawtooth" pattern, and the pumping pressure drops signifcantly with multiple injections, which is a hydraulic driling for the rolor='red'>of lor='red'>of the broken slor='red'>oft low-permeability coal seam. The typical pressure curve lor='red'>of fracturing shows that the hydraulic fracturing scheme is scientific and reasonable.
(4) After adopting the rolor='red'>of hydraulic fracturing technology, under the conditions lor='red'>of large flow and high pressure hydrodynamics, the storage pressure lor='red'>of the coal seam is effectively reduced, and the overlying rock layer lor='red'>of the coal seam is cracked, expanded, and extended. As the fracturing continues, the formation The artificial fissures and natural fissures and the weak surfaces lor='red'>of coal-rock joints are effectively connected, and the effective communication between the fissure network and the free surface lor='red'>of the outside world improves the permeability lor='red'>of coal and rock masses and provides a good channel forgas migration and flow. It was able to relieve the pressure and increase the permeability, break the original stress lor='red'>of the coal seam and the state lor='red'>of gas occurrence, and the gas was continuously desorbed within 3 months, indicating that the Wangfeng Coal Mine rolor='red'>of directional hydraulic fracturing has achieved ideal results, and the plan is feasible and popular.
 

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