A hybrid up scaling procedure for modeling of fluid flow in fractured subsurface formations

摘要

Natural fractures reside in various subsurface formations and are at various length scales with different intensities. Fluid flow in fractures, in matrix and between matrix and fractures are following different flow physics. It is thus a great challenge for efficiently modeling and simulation of fluid flow in fractured media due to the multi-scale and multi-physics nature of the flow processes. Traditional dual-porosity and dual-permeability approach represents fractures and matrix as different continuum. The transfer functions or shape factors are derived to couple the fluid flow in matrix and fractures. The dual-porosity and dual-permeability model can be viewed as a multi-scale method and the transfer functions are used to propagate fine-scale information to the coarse-scale reservoir simulation. In this paper, we perform a detailed study to better understand the optimal way to propagate the fracture information to the coarse-scale model based on the detailed fracture characterization at fine-scale. The Discrete Fracture Modeling (DFM) approach is used to represent each fracture individually and explicitly. The multiple sub-region (MSR) method is previously used for up scaling calculations based on fine-scale flow solution by finite volume method on the DFM. The MSR method is the most appropriate up scaling procedure for connected fracture network but not for disconnected fractures. In this paper, we propose an adaptive hybrid multi-scale approach that combines MSR and DFM adaptively for up scaling calculation for complex fractured subsurface formations that usually involve both connected fracture network and disconnected fractures. The numerical results suggest that adaptive hybrid multi-scale approach can provide accurate up scaling results for flow in a complicated geological system.