Characteristics of Hydraulic Fracture in Homogeneous Porous Rock Material Based on EPHF Model

Based on a coupled fluid-solid theory, an extended permeability-based hydraulic fracture(EPHF) model was developed according to the permeability-based hydraulic fracture(PHF) model. The proposed EPHF model assumed that the permeability of porous rock was a function of mean effective stress when a rock was fractured. The porous elastic constitutive law and Drucker-Prager plastic model were adopted to model the pre-failure and post-fracture process of rock material, respectively. The Darcy's law was used to describe the liquid phase. To consider the influence of injection fluid, the LET model was integrated to modify the permeability of fracture zone with the mixed viscosity of injection and original fluid being used. The development of pore pressure, stress path, equivalent fracture zone and fracture height for different tensile strength were studied by using the proposed model. The simulation results indicated that the pore pressure in fracture path(except injection point) first decreased and then increased to propagation pressure. If the effective stress difference and pore pressure were kept the same or if the total stress was constant, the breakdown pressure decreased when the effective stress ratio increased.