Simulation of hydraulic fracturing in brittle rocks

Abstract

[Abstract]: To investigate the breakdown pressure and the energy transferred to the surrounding rock, numerical simulations of circular boreholes under internal hydraulic pressure are carried out. For this purpose, a micromechanical continuum damage model proposed by Golshani et al. [1] is used. The simulation results show that the borehole breakdown pressure and the energy transferred to the surrounding rock are dependent on the mechanical properties of the rock, borehole size and far-field confining stresses. Although the energy transferred to the surrounding rock increases with increasing borehole size, the borehole breakdown pressure decreases. The analysis also shows that breakdown does not occur even if a crack initiated at a borehole wall. In fact, the breakdown occurs when the crack growth becomes unstable. In other words, breakdown pressure appears to correspond to the onset of unstable crack growth.