Discrete and smeared fracture model to simulate fluid flow in naturally fractured reservoirs

摘要

The production of naturally fractured reservoirs is highly influenced by these features, which increases the permeability and alter the flow trajectory and the pressures in the reservoir. Studies of fluid flow in fractured media have recently gained interest due to the high productivity of the naturally fractured deposits. The networks of fractures within the reservoir vary in aperture, length-scale and density of fractures. The larger scale fractures form intercommunicated channels of high permeability, while fractures of medium and small scale enhance rock porosity. Larger scale fractures are typically modeled using discrete fracture model (DFM). However, discrete fracture models have reduced applicability for complex fracture networks formed by small-to medium-scale fractures. Smeared fracture models are an alternative in such cases. The hydro-mechanical formulation for smeared fracture is implemented in the finite element method (FEM), using dual porosity and dual permeability (DPDP) model. Mechanical and hydraulic examples are presented. The geomechanical strain changes in the fractures are considered in order to study its impact on the fluid flow and pressure dissipation. The results are compared with discrete fracture model and conventional simulations of single porosity in order to get a better understanding of two media superposition effects. In the hydraulic example, several geometrical transfer functions are studied to choose the most accurate regarding the discrete fracture model results. Finally, the transfer factor chosen is used in the presented hydro-mechanical examples. The good results support the application of the smeared fracture model to represent fractured media with multiscale length fractures.