Approximate Analytical Solutions for 1-D Immiscible Water Alternated Gas

Abstract

Water Alternated Gas (WAG) flooding is largely used as an Enhanced Oil Recovery (EOR) method in oil fields. It is based on the high sweep efficiency of the water phase and the high displacement efficiency of the gas phase. Additionally, other components may be dissolved in both displacing phases, increasing the oil recovery factor and leading to modern WAG schemes such as PWAG (Polymer WAG), MWAG (Miscible WAG), and others. In this paper, we present approximate analytical solutions for the linear immiscible Water Alternated Gas problem. The mathematical model is composed by a 2×2 system of nonlinear hyperbolic Partial Differential Equations (PDE), solved by the Method of Characteristics (MOC) for a set of reservoir properties. The analytical solution is compared with numerical simulation showing the accuracy and robustness of the method under different WAG configurations. The presented solutions can be used to select the best recovery technique for a particular field in a fast and efficient way.