Optimal Control of Polymer Flooding for High Temperature and High Salinity Reservoir

Polymer flooding is one of the most important enhanced oil recovery (EOR) technologies for high temperature and high salinity reservoir. In this paper, an optimal control model of distributed parameter systems (DPS) for polymer injection strategies is established, which involves the performance index as maximum of the profit, the governing equations as the fluid flow equations of polymer flooding in high temperature and high salinity reservoir, and some inequality constraints as polymer concentration and injection amount limitation. The optimal control model is discretized by full implicit finite difference method. To cope with the discrete optimal control problem (OCP), the necessary conditions for optimality are obtained through application of the calculus of variations and Pontryagin’s discrete maximum principle. A gradient method is proposed for the computation of optimal injection strategies. The numerical results of an example illustrate the effectiveness of the proposed method.