An Analytical Model for Fracture Initiation of Radial Drilling-Fracturing in Shale Formations

Abstract Radial drilling-fracturing, the combination of radial drilling and hydraulic fracturing, can guide fractures toward target area effectively enhance recovery low permeable reservoir. In this paper, based on stress superposition principle, we establish an analytical model to predict fracture initiation pressure (FIP) shale failure mode for drilling-fracturing applied in formations. contrast with former studies, additionally consider from beddings is more applicable The classifies into three modes and, respectively, gives criterion each mode. Then, a series sensitivity analyses conducted by examining effects various parameters. By analyzing variation characteristic pressures required modes, main conclusions are as follows. Firstly, matrix shear along bedding tend take place when azimuth borehole moderate. Small large azimuths favorable occurrence tensile bedding. Secondly, high ratio horizontal situ predisposes generate failure, apt occur low. Thirdly, increasing intersection angle wall plane, changes then failure. Fourthly, prefers yield under small Biot coefficient other two large. Fifthly, permeability virtually has no influence shale. research clarifies characteristics formations provides reference field application drilling-fracturing.