Characteristics of Hydraulic Fracture in Heterogeneous Rock with Distributed Hard Inclusions

Hydraulic fracture is an important technic for oil/gas production. A smeared cracked method is adopt for simulating hydraulic fracturing propagation within the framework of a fully coupled, pore pressure-solid phase interaction formulation. The stress-strain behavior of the solid phase is modeled as a porous media by using elasto-plastic, Drucker-Prager description. The inherent assumption of the fracture model is that the permeability can be expressed as a function of the difference between the mean effective stress and the tensile strength of the rock. For two-phase flow, the relative permeability is used for including the effect of fluid mixture between the original fluid and injection fluid. The rock sample with randomly distributed irregular hard inclusions is studied with the vertical stress, horizontal stress and pore pressure being 29.13 MPa, 19.77 MPa and 10.34 MPa, respectively. By running over 30 numerical cases, the characteristics of injection pore pressure and equivalent opening versus injection time are well simulated with different relevant dynamic viscosity, injection rate, intrinsic conductivity and tensile strength. Finally, the paper ends with some useful observations on the characteristics of hydraulic fracture.