Miscible displacement simulation and permeability characterization in porous media.

摘要

This study develops a three-dimensional simulation to describe single phase flow in porous media. It is applied to two distinct applications: the reproduction of published experimental results for miscible displacements and the characterization of porous media samples.;Virtually the only enhanced oil recovery process that has been commercialized is one in which a miscible fluid such as CO2 is employed to displace the oil. The problem with such a process is that the displacement is unstable because the viscosity of the displacing fluid is less than the viscosity of the displaced fluid, oil. As a result, the CO2 forms narrow channels (or viscous fingers) through the oil, bypassing much of it and rendering the process much less efficient than it could be. In addition to viscosity differences, the density differences between the two fluids can lead to the displacing fluid passing over the displaced fluid. This flow pattern, known as gravity tongues, can also greatly impact the displacement efficiency. To better understand these phenomena, a highly accurate, three-dimensional computer simulation of the displacement process is developed. The simulator is used to reproduce experimental displacement data.;The aforementioned laboratory miscible displacement experiments are performed on bead packs that are essentially homogeneous. Unfortunately, most natural porous media formations are heterogeneous, possessing an absolute permeability that varies as a function of position. In order to simulate flow processes for these porous media samples, a detailed description of the internal absolute permeability field is required. There exists no experimental procedure or instrument that will allow for the direct measurement of the permeability variation within a porous media sample. Instead, the permeability must be inferred by using associated experimental measurements and a mathematical model that relates them to the permeability. This study develops a methodology for determining the absolute permeability distribution in a porous media sample using the velocity data generated in NMR imaging experiments.