A three‐dimensional enhanced dual‐porosity and dual‐permeability approach for hydromechanical modeling of naturally fractured rocks

Abstract

AbstractThe natural fracture system plays an important role in the development of naturally fractured reservoirs. Traditionally, those reservoirs are simulated using dual‐porosity and dual‐permeability models. Conventional dual‐porosity models adopt over‐simplifications in terms of characterization of the fractured system. Generally, they focus on the hydraulic problem and do not consider the rock and fracture deformability. Besides, those models assume equally sized block matrix and orthogonal fracture sets with uniform properties. This work proposes a new hydromechanical formulation to represent a fractured porous formation more realistically using the finite element method. The enhanced dual‐porosity and dual‐permeability (EDPDP) model allows incorporating multiblock domains formed by several multiscale fracture sets with arbitrary orientations, permeabilities, and sizes. The fully coupled hydromechanical formulation includes fracture orientations and stress‐induced aperture changes to update stiffness and permeability tensors. The EDPDP model is implemented in an in‐house framework to study the effects of fractures with multiple scales on a hydrocarbon reservoir's hydromechanical behavior. We compare the proposed model against the discrete fracture method to assess its accuracy. The comparative results show excellent agreement and validated the fully coupled hydromechanical formulations. Finally, we present a case study of a reservoir that contains multiple sets of fractures with different scales and arbitrary orientation to demonstrate the applicability and robustness of the proposed model.