Simulation of Hydraulic Fracture Propagation in a Naturally Fractured Reservoir

Abstract

Hydraulic fracturing in a naturally fractured formation often leads to a complex fracture networks. The problem of induced and natural fracture interaction has been the subject of many theoretical, experimental and numerical studies. In this work, we develop a 2D displacement discontinuity-based method for HF/NF interaction. The approach considers the deformation of natural fractures when simulating the hydraulic fracture propagation. This is achieved by using an explicit solid-fluid mechanics coupling. The model solves the governing equations for fracture width, pressure, and fracture trajectory as a function of time. An Extended Neuber-Novozhilov structural fracture propagation criterion (Dobroskok et al. 2005) is used to find the fracture propagation path based on the tensile driving force and the shear driving force ahead of the crack. The fluid-flow in the NF system is coupled with a contact element algorithm to investigate the natural fracture closure and opening with respect to fluid pressure. The effect of initial deformations of pre-existing fractures on HF is modeled. The simulation results show the possible locations for fracture initiation along natural fractures as well as the locations of width constriction on HF/NF system. The displacement discontinuity method also accurately calculates the stress distributions and stimulated volume in the fracture network.