碎软煤层井下多点定向长钻孔水力压裂技术
Long Multi-point Underground Directional Drilling Hydraulic Fracturing Technology for Low-permeability Weak Coalbed
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摘要: 针对低透气性碎软煤层普遍存在的瓦斯抽采效果差的技术问题，研究了多点定向长钻孔水力压裂高效瓦斯抽采技术, 探讨了碎软低透气性煤层的水力压裂增透机理；在施工多点定向长钻孔、井下水力压裂快速封孔装备的基础上，进行了煤矿井下水力压裂现场试验；分析了压裂过程中参数变化规律，提出了水力压裂影响范围、压裂效果和瓦斯抽采效果评价方法，并进行了效果考察。结果表明：该技术提高了井下水力压裂封孔效率和施工质量，改善了试验区域的煤储层参数，水分提高了4.31倍，透气性提高了4.88倍；水力压裂影响范围沿钻孔径向影响范围50～60 m；沿着钻孔轴向最大影响范围约40 m。压裂后连续抽采233 d累计抽采纯瓦斯量为25.14×104 m3，日最高抽采量3 077.41 m3/d，瓦斯含量降低了34.67%。Abstract: For the technical problems of poor gas extraction effect in low permeability and soft coal seam, the paper studies the high efficiency gas extraction technology by long multi-point directional drilling hydraulic fracturing, and discusses the mechanism of hydraulic fracturing and permeability improvement in low-permeability weak coal seam. On the basis of constructing the long multi-point directional drilling and the quick hole sealing equipment of underground hydraulic fracturing, the field test of hydraulic fracturing in underground coal mine is carried out. This paper analyzes the laws of parameter variation during fracturing, and proposes the influence range of hydraulic fracturing, fracturing effect and the evaluation method of gas extraction, and carries out the effect investigation. The results show that this technology improves the hole sealing efficiency and construction quality of underground hydraulic fracturing, improves the parameters of coal reservoir in the test area, the water content increased by 4.31 times, and the permeability increased by 4.88 times; the influence range of hydraulic fracturing is 50 m to 60 m along the radial of borehole; the maximum impact range along the axial direction is about 40 m. Continuously extracting 233 d after the fracturing, and the cumulative gas extraction is 25.14 × 104 m3, the daily maximum extraction amount is 3 077.41 m3/d, and the gas content decreased by 34.67%.
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