Coupled Geomechanics and Flow Simulation for an Embedded Discrete Fracture Model

Abstract

Abstract The effect of geomechanics on fluid flow is more crucial in fractured reservoirs due to presence of fissures, which might be more stress-sensitive than the rock matrix. The flow characteristics of fractures are significantly affected by effective normal stress exerting on them. In spite of extensive experimental and field studies that have demonstrated the dynamic behavior of fractures, fracture properties have been often treated as static parameters in the simulations of naturally fractured reservoirs. Realistic modeling of production in fractured systems requires including the dynamic behavior of fractures into a discrete fracture model. We have incorporated the dynamic behavior of fractures into an embedded discrete fracture model, called EDFM. The coupled model allows inclusion of the impact of stress regime on fluid flow in a 3D discrete fracture network. We use empirical joint models to represent normal deformation of pre-existing natural fractures and couple them with the EDFM approach. Using these models, the aperture and permeability of an arbitrary-oriented fracture become functions of the effective normal stress acting on the fracture plane. In addition, we allow for fracture-conductivity tables to model dynamic behavior of propped hydraulic fractures in stimulated reservoirs. We present several examples in this study to show the applicability and performance of the coupled geomechanics-EDFM approach for the simulation of naturally fractured reservoirs. We examine the effect of pressure-dependent fracture properties on production leading to the conclusion that fracture deformation, caused by effective stress changes, substantially affects hydrocarbon recovery. Our simulations show that the significance of such effects on production strongly depends on parameters controlling the deformation behavior of fractures. Simulations also show that creating sufficiently high-conductivity fractures during stimulation treatment of unconventional reservoirs can mitigate the adverse effect of hydraulic fracture closure on production to a good extent. Furthermore, the coupled geomechanics-EDFM approach does not degrade the computational performance of EDFM, which is a promising new approach for modeling discrete fractures in a robust and efficient manner.