Simulation of Hydraulic Fracturing-Induced Permeability Stimulation Using Coupled Flow and Continuum Damage Mechanics

Abstract

Abstract In hydraulic fracturing operations, permeability is enhanced when fractures are created and/or stimulated by injecting a highly pressurized fluid. In addition, mechanical response of the rock changes because of permanent modifications in the structure and properties of the rock after failure. In order for engineers to accurately predict results of hydraulic stimulation projects, mathematically rigorous and numerically efficient models of fluid flow and geomechanical deformation in fractured porous media must be used in computer simulations. Some of the earlier approaches address the problem of fluid flow through fractured media with mathematical models that are either too simplistic or too expensive computationally and are not compatible with the available petroleum reservoir simulation platforms. In this work, a reservoir simulation framework is developed using a sequentially coupled numerical scheme of flow, deformation and poromechanical damage to study variations occurring in the fractured rock properties and state variables as a result of hydraulic stimulation. We numerically simulate injection-induced permeability enhancement and plastic deformation as well as post-stimulation softening behavior of the rock by considering the stimulated rock as a mechanically damaged configuration, the properties of which are modeled using an effective continuum model. We study how the flow and mechanical properties of fractured rock, namely permeability and stiffness, change by virtue of hydraulic fracturing, and we investigate the dynamics of pressure distribution and stress state with time. The sequential nature of the proposed coupling framework lends itself to easy integration with reservoir simulation and prediction tools.