The effects of injection source inclination, stratified permeability heterogeneity and permeability anisotropy on the miscible flooding of porous media.

摘要

This work focuses on the 2D numerical simulation and analysis of the miscible displacement of porous media for (1) inclined injection sources in a homogeneous, isotropic permeability medium, (2) vertically and horizontally oriented injection sources in a vertically heterogeneous (i.e., stratified) permeability medium and (3) vertically and horizontally oriented injection sources in a homogeneous, anisotropic permeability medium. This research is formulated primarily for application to conditions encountered in the miscible flooding of oil-bearing rock formations.; We utilize a finite-difference numerical simulator, with spectral methods used to solve Poisson's equation and a 6th order compact finite difference scheme used for spatial derivatives. Time stepping is performed using the Alternating-Direction-Implicit (ADI) method. A grid of 2048 horizontal points and 200 vertical points is employed to ensure that all features of the simulations are adequately resolved.; Our results indicate that linear flow from an inclined injection source in a homogeneous, isotropic permeability medium results in a completely different displacement mechanism than that from a vertical injection source. In the presence of moderate buoyancy forces, and as the stability of the interface decreases with an increasing mobility ratio, the flood fronts gravitate to two basic flow scenarios, depending on which side of the injection source one is observing. On one side, a rapidly moving gravity tongue develops that propagates faster than is possible in a vertical injection source scenario. On the other side, the flood front becomes a competition of viscous versus buoyancy forces, with a variety of possible outcomes depending on the balance of forces.; The basic results of our comparison of horizontal versus vertical injection sources indicates that, with buoyancy forces present, (1) horizontal injection sources perform equal to or better than vertical ones under homogeneous, isotropic permeability conditions, (2) vertical injection sources perform better than horizontal ones under vertically heterogeneous permeability conditions and (3) under homogeneous, anisotropic permeability conditions, either outcome is possible depending on the interplay of viscous and buoyancy forces.