Integrated discrete fracture and dual porosity - Dual permeability models for fluid flow in deformable fractured media

Aiming at accuracy and computational efficiency, integrating discrete fracture and dual porosity-dual permeability models is a viable alternative to simulate flow in naturally fractured reservoirs with discontinuities of multiple lengths. However, previous works focus on the hydraulic problem only and do not take into account geomechanical effects. This study proposes a hydro-mechanical model using the finite element method (FEM) to represent the behavior of fracture networks with fractures of large, medium and small lengths. The methodology integrates the discrete fracture model (DFM) using interface elements, and the dual porosity/dual permeability (DPDP) model. Some synthetic applications compare the results of the models. A case study integrating both approaches is also performed. The results show that fractures of small and medium length enhance the permeability of naturally fractured reservoirs. Their presence within the porous medium results in greater fluid drainage and faster rate of pore pressure dissipation. The fractures contributed significantly to the mechanical behavior with impact on the stiffness of the rock mass system. Aperture variation of the fracture network influences fracture permeability and shows the stress shadowing effect. The results support the application of the proposed large-medium-small length fracture model to represent enhanced permeability of naturally fractured media.