Research and Application of Directional Hydraulic Fracturing Technology

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. In this paper, 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. The result shows that: when directional drilling is set on the center line between hydraulic fracturing drillings and the distance of hydraulic fracturing drilling and the directional is 3 -4m, 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.