Estudo numérica do processo de deslocamento de fluidos em meio poroso heterogêneo usando o método de Lattice Boltzmann

Abstract

In the present work, the process of immiscible fluids displacement in a heterogeneous porous medium is numerically studied for the purpose of investigating the sweep efficiency during the oil recovery process. The objective of this work is to understand the influence of viscous and capillary parameters (viscosity ratio and capillarity number), wetting effect (static contact angle) and porous media properties (porosity and pore shape). For this, the immiscible fluids displacement is simulated considering the injection of fluid into a porous channel filled by another fluid. The porous channel is idealized to two-dimensional plane, where the heterogeneous porous medium is represented by fractal geometry orders of the Sierpinski carpet. The boundary conditions are applied as a fully developed flow of the injected fluid at the inlet of the channel, constant pressure at the outlet of the channel and no slip of the fluids on the solid surfaces. The fluids displacement through the porous medium is modeled numerically using the Lattice-Boltzmann method, which has a mesoscopic approach based on kinetic particle theory, consisting of a discretized form of the Boltzmann equation that simulates the problem by collision and streaming of particles. The results obtained demonstrate agreement on the behavior of the capillary number and viscosity ratio effects, with other results observed in the literature, and it is possible to identify the transition between the states of viscous fingering, capillary fingering and stable displacement. In relation to the influence of the wettability it is observed the increase of the sweep efficiency with decrease of the static contact angle for both the imbibition and the drainage process. In the analysis of the parameters related to the structure of the porous medium, in general, a reduction of the sweep efficiency with the reduction of the porosity is observed, however, it is observed the increase of the sweep efficiency for the second order of the Sierpinski carpet, interpreted as a result of the decrease of the recirculation regions of the flow due to the reduction of the porosity.