Experimental And Mathematical Study Of Multi-Component Gas/Oil Displacement With Constant Pressure Boundaries

Abstract

In this paper multi-component gas/oil displacements with constant pressure boundaries are studied mathematically and experimentally. Mathematically, a novel generation of Buckley-Leverett’s classic fractional flow theory is applied to analytically solve the problem of multi-component gas/oil displacements under constant pressure boundaries. Experimentally, slim tube tests under constant pressure boundary condition are conducted to validate the assumptions made in the mathematical section and thus confirm the innovative analytical solution. All the previous studies in gas/oil displacement problems have been accomplished under the assumption of constant flux boundaries. In practice however, gas flooding projects are often conducted with constant injection pressure and constant producing well pressure. Therefore, a fast and accurate analytical solution will be a powerful tool for IOR/EOR scenario simulations. Conservation of mass in a one-dimensional, dispersion-free medium, for a multi-component gas/oil displacement system leads to a set of partial differential equations. The solution of the corresponding initial value problem under constant flux boundary conditions consists of rarefaction waves, shock waves and constant states connecting the injection state to the production state. In incompressible systems with constant pressure boundaries, the total volumetric flux is a function of time and hence, the classical Buckley-Leverett theory is not valid. However, the saturation wave structure obtained from the constant flux boundary condition problem can be used in the solution of the associated problem with constant pressure boundaries by determining the flux analytically as a function of time. The experimental and analytical solution for a multi-component gas/oil displacement case study is presented. The determination of time dependent volumetric flux from the analytical solution of the constant flux problem is demonstrated. Experimental results are analyzed and compared with the analytical solution. This indicates that analytical solutions match with the experimental results if reliable relative permeability data are used. Key Words: Multi-component gas injection, constant flux boundary condition, constant pressure boundary condition.