Dynamic optimization of polymer flooding for high-salinity reservoir based on maximum principle

Polymer flooding for high-salinity reservoir is one of the most important technologies for enhanced oil recovery (EOR). In this paper, an optimal control problem (OCP) of a distributed parameter system (DPS) is established, in which the functional of performance index is profit maximum and the governing equations are the fluid equations in porous media. The control variables are chosen as the polymer concentrations. The constraint conditions include boundary constraints and other inequality constraints. To cope with this OCP of DPS, the necessary conditions for optimality are obtained through application of Pontryagin´s maximum principle. A gradient method is proposed for the computation of optimal injection strategies. The numerical results of an example for high-salinity reservoir illustrate the effectiveness of the proposed method.