水力压裂纵向切槽钻头的研制与试验

Development and test of longitudinal slotting drill bit for hydraulic fracturing

为解决采用常规水力压裂进行强烈动压巷道切顶卸压效果难以控制的问题,研发了一种钻孔内纵向切槽钻头,进行了一系列实验室试验和井下试验。研究结果表明,纵向切槽钻头可有效实现孔内纵向切槽,引导水力压裂主导裂缝沿切槽方向起裂和扩展,满足强烈动压巷道水力压裂切顶卸压要求,切槽效率比传统的横向切槽钻头效率提高30%~50%;何家塔煤矿井下试验表明,纵向切槽水力压裂主导裂缝沿巷道轴向起裂和扩展,扩散范围达20~30 m,起裂压力明显小于常规水力压裂的起裂压力;受工作面回采影响后纵向切槽水力压裂段煤柱应力增量相对普通水力压裂段和未压裂段明显较小,切顶卸压效果明显好于普通压裂段和未压裂段;纵向切槽水力压裂切顶卸压段工作面端头三角区悬顶长度平均3.7 m,明显小于常规压裂段和未压裂段平均悬顶长度6.2 m和8.0 m,且顶板断裂较为整齐。

In order to solve the problem that it is difficult to control the effect of roof cutting and pressure relief of strong dynamic pressure roadway by conventional hydraulic fracturing,a longitudinal grooving bit in borehole was developed,and a series of laboratory tests and downhole tests were carried out.The research results show that the longitudinal grooving bit can effectively realize the longitudinal grooving in the hole,guide the main fracture of hydraulic fracturing to start and expand along the grooving direction,meet the requirements of hydraulic fracturing top cutting and pressure relief for strong dynamic pressure roadway,and the grooving efficiency is 30%~50% higher than that of the traditional transverse grooving bit.The underground test in Hejiata Coal Mine shows that the main fracture of longitudinal grooving hydraulic fracturing starts and expands along the axial direction of the roadway,with a diffusion range of 20~30 m,and the starting pressure is obviously lower than that of conventional hydraulic fracturing.The stress increment of coal pillar in the longitudinal grooving hydraulic fracturing section is obviously smaller than that in the ordinary hydraulic fracturing section and the non fracturing section after the influence of the mining of the working face,and the pressure relief effect of the top cutting section is obviously better than that in the ordinary fracturing section and the non fracturing section.The average suspended top length of the triangular area at the end of the working face in the top cutting and pressure relief section of the longitudinal grooving hydraulic fracturing is 3.7 m,which is obviously smaller than the average suspended top length of 6.2 m and 8.0 m in the conventional fracturing section and the non fracturing section,and the roof fracture is relatively neat.