Water slug injection containingnpolymers in porous media

Abstract

Injection of water containing dissolved chemicals is an efficient oil recovery technique. One of the problems of this method is the loss of the chemical components due to interactions between rock and fluid. In polymer injection, adsorption may happen and lead to low process efficiency. The interaction between rock and fluid is governed by the adsorption isotherm, which relates the polymer concentration in water with the adsorbed amount on the rock. In this paper the problem of oil displacement by a water slug containing n chemical components that may be adsorbed is analyzed. The system of conservation laws is solved and the structure of the solution for the case of Henry´s adsorption isotherm is completely described. The concentration profile of each component and the chromatographic cycle is calculated through simple expressions. The complete and detailed solution for the case of slug injection containing three chemical components is presented. The general solution developed can be used to model several Enhanced Oil Recovery techniques, in which the chemical components adsorb in porous media following Henry's adsorption isotherm. K E Y W O R D S chemical enhanced oil recovery, conservation laws, enhanced oil recovery, hyperbolic systems of partial differential equations, polymer flooding 1 | INTRODUCTION Different techniques can be employed to improve recovery in oil fields. Water injection is the most used and the one-dimensional mathematical problem was solved analytically. 1 It was considered immiscible and incompressible phases (oil and water). Adding polymer to the injection water reduces water mobility and modifies the fractional flow curve, hence increasing the sweep efficiency. Chemical enhanced oil recovery (EOR) has been applied in onshore and offshore petroleum fields. The most used chemical components dissolved in the injected water are polymer, surfactants, and alkalis. This technique recovers part of the remaining oil mainly due to a favorable mobility ratio change. One of the first offshore chemical EOR projects took place at West Bay and Quarantine Bay Field, in Louisiana shallow waters, in 1981. Later, other chemical EOR projects were applied in Cuadras