定向水力压裂技术研究与应用

摘要

Aiming at the problem of stress concentration caused by uncertain direction of permeability improvement after hydraulic fracturing in coal mine, directional drilling technology for hydraulic fracturing was presented. The necessity of directional hydraulic fracturing and the current research status were introduced, the function mechanism of directional drilling was analyzed, parameters including position and interval were determined, and the effect of oriented control was verified by means of numerical simulation : when directional drilling is set on the center line between hydraulic fracturing drillings and the interval between hydraulic fracturing drilling and the directional is 3 ~4 m, directional drilling plays a role of auxiliary free surface which has an active effect on orienting and accelerating the expansion of fractures produced by hydraulic fracturing. Directional drilling induces fractures to grow from hydraulic fracturing drilling to the directional so as to prompt the transfixion between hydraulic fracturing drillings, eliminates stress concentration, and achieves an effect of whole pressure relief. After field test of cross-seam directional hydraulic fracturing, both the values and the change ranges of index q and s of coal and gas outburst risk in work face are reduced, the driving speed is increased by 69% and production safety is realized.%针对煤矿井下实施水力压裂措施后增透方向不确定导致应力集中的问题,提出了定向孔定向水力压裂技术.介绍了定向水力压裂的必要性及当前研究现状,分析了定向孔定向作用机理,确定了定向孔的布置位置、间距等参数.利用数值模拟软件验证了定向孔的导向控制效果.分析结果表明:在压裂孔连心线上布置定向孔.定向孔与压裂孔间距为3～4m时,定向孔起到了辅助自由面的作用,对压裂产生的裂隙具有导向和加速扩展的作用.定向孔诱导裂隙从压裂孔周围向定向孔方向发展,进而促使压裂孔之间实现贯通,消除了应力集中,达到了整体卸压增透的效果.现场实施穿层定向水力压裂后,工作面瓦斯突出危险性指标q值、S值减小,变化幅度降低,掘进速度提高了69％,实现了安全生产.