An efficient finite difference model for multiphase flow in fractured reservoirs

Abstract

Considering the discontinuities of flow phase saturations at the matrix-fracture interfaces, a new difference model is proposed to simulate the multi-phase flow in reservoir with conductive fractures. Structure grids are applied in the simulation to divide reservoir regions, fracture grids are embedded in matrix grids, and reference nodes are chosen to define the exchanges between fracture and two sides of matrix. During solving the matrix equations, the discontinuities of phase saturations also lead to difficulties for defining the physical quantities on the matrix grids covering fracture, and to avoid this difficulty, inner boundary is used to replace these matrix grids in the computations. This model is used to simulate the reservoirs with straight and inclined fractures, and compared with discrete fracture model and embedded fracture model. The comparison shows that: no matter in fracture or matrix, the results from the new model are in good agreement with the discrete fracture model, but embedded fracture model has some error; the new fracture model can significantly improve the efficiency of simulation. Key words: fluid flow, multi-phase flow, reservoir simulation, conductive fracture, difference model