Numerical Simulation Of Two-phase Fluid Flow In Fractured-vuggy Media

Fractured-vuggy carbonate reservoir is a kind of special reservoir and its geological character is extremely heterogeneous. Reservoir space is complicated and caves and fractures are the main room for preserving and transporting in this kind of reservoir. The flow pattern in fractured–vuggy reservoir is complicated because of its variable pore structure and the flow mechanism in it is still not clear. So it is important and necessary to study the flow mechanism in it for enhancing oil recovery of fractured-vuggy reservoir.In this paper, on the base of analyzing and summarizing of reservoir space, fractured-vuggy media conceptual model are constructed by further simplifying its geological structure. The mathematical model of oil/water two-phase flow in fractured-vuggy media is established by allying the continuous equation, N-S equation and Level Set equation, and relevant equations for finite element calculation are derived. The finite element numerical analysis software COMSOL Multiphisics is used to simulate the process of oil/water displacement in one-fracture conceptual model and one-fracture and one-vug conceptual model. The flow pattern, swept area, waterflood front and residual oil distribution are analysed. system. The main achievements acquired in this paper lie in the following:①The water-flooding process is classical piston displacement in standard rectangular.fracture;②For the one-fracture and one-vug conceptual model, when the pressure difference is less than 100Pa, waterflood front in the vug moves homogenously and symmetricly. The residual oil mainly locate in the four vug corner and the residual oil in left two corners is larger than that in the right two corners. With the pressure difference increase to 200Pa, there is an increasing trend that water phase move forward along the central axes to the exit of vug. When waterflood front reach the exit of vug, the simulation oil on both sides of the cavity is not swept. The fluid striking at the left wall of the cavity is blocked, countercurrent form and swirlpool appear in the cavity. When the pressure differenc continuously increase to 500Pa, there is apparent reflected flux at the two ends of the exit of cavity. Because of the entrainment, some simulation oil was confined in the whirlpool.The innovative point in this thesis is that it applied the Level Set method developed recently to track the evolution of oil/water interfaces in fractured-vuggy media.The numerical simulation of water-displacing oil deepened the understanding of the mechanism of two-phase fluid flow in fractured-vuggy media, and it would play an important role in directing the recovery of fractured-vuggy carbonate reservoir.