Multiscale Finite Element Simulation Of Fluid Flow In Carbonate Reservoir

The difficulty in analyzing multi-phase fluid flow in carbonate reservoir is mainly caused by the heterogeneity of subsurface formations spanning over many scales.One of the major challenges in reservoir simulation is posed by the existence of multiple scales in reservoirs and the resulting high resolution geophysical models.On the other hand,the accuracy of simulating subsurface flow relies strongly on the detailed geophysical properties of natural heterogeneous formations.The direct numerical solution of multiple scale problems is difficult even with the advent of supercomputers.If one can perform upscaling(or averaging)and simulate a process over the entire region,the numerical results cannot capture the small-scale effect on the large scales.Therefore,it is desirable to develop a method that simulate the multiscale fluid flows in carbonate reservoir,but does not require resolving all the small-scale features.The fundamental principles of multiscale finite element method are first introduced,including the construction of multiscale basic functions,the boundary conditions of basic functions and the oversampling method.In this dissertation,we proposed a multiscale locally conservation finite element to simulate the two-phase fluid flow in heterogeneous reservoirs.It can overcome the shortcomings of traditional multiscale finite element method.Then,considering three different flow patterns,i.e.incompressible flow,compressible flow and nonlinear flow,multiscale methods have been used to simulate the fluid flow.The comparisons between our reference solutions and multiscale results indicate that our methods are more effective.Multiscale finite element method has been also used to model the fluid flow in the fractured porous media based on the discrete fracture model.The multiscale method has been applied only to the flow problem for efficient solutions of the pressure and velocity fields,while the transport problem is solved on the fine scale.At last,due to the co-existence of porous and free-flow in fractured vuggy porous media,based on and discrete fracture-vug network model,multiscale finite element method and generalized multiscale finite element method have been used to model the fluid flow in such region.Some numerical examples have been used to demonstrate the validity of the method.Summing up,an efficient fluid flow model and its modeling theory have been developed in this dissertation,which can be applied to the carbonate reservoirs.