AN EQUIVALENT CONTINUUMAPPROACH FOR MODELING TWO-PHASE FLOW IN FRACTURED-VUGGY MEDIA

摘要

Modeling and numerical simulation of fluid flow in fractured-vuggy media (FVM) is a challenge due to the coexistence of multiscale void spaces filled with fluid and a complex topology configuration. Ane quivalent continuum approach is proposed for estimating the equivalent permeability tensor (EPT) and modeling two-phase flow with a full permeability tensor. A coupled Stokes-Darcy model is presented to estimate the EPT of a fracture-vug-media system. The operation of two-step mirror imaging is applied to any original block with a symmetric boundaries so as to form a new grid block having symmetric boundaries with periodic boundary conditions. A pretreatment approach for fractured media is developed to replace each fracture and surrounding porous media with continuous media characterized by equivalent permeability. The mixed finite element (MFE) method based on the first-order Brezzi-Douglas-Marini (BDM) space and the discontinuous Galerkin (DG) method are used to solve the pressure equation and the saturation equation for the two-phase flow problem in an equivalent region characterized by a permeability tensor. Several examples are addressed to show the feasibility,validity,and applicability of the methodology in calculating the EPT of FVM and simulating two-phase flow using a permeability tensor, and to illustrate the advantages of integrating complex flow calculations offered by the continuum model with the realism of FVM systems as captured by the discrete model.