Surfactant-Polymer Interactions in Tertiary Oil Recovery

Abstract

Dilute aqueous surfactant and polymer solutions are used to displace the trapped oil from the porous reservoirs in the tertiary recovery process, by virtue of their interfacial tension lowering and mobility control characteristics, respectively. The interactions that occur between the surfactant and the polymer solutions, however, lead to the formation of a polymer-surfactant complex and phase separation thus resulting in the loss of the chemicals and the modification of the designed solution properties of the surfactant and of the polymer. For the purpose of characterizing apriori, the type of polymer suitable for the tertiary recovery process, a simple model is developed here to predict the extent of the surfactant binding to the polymers in dilute aqueous solution. The model is based on the premise that the intra-molecular contacts between the polar and the non-polar segments of the polymer can be visualized as the analogs of the macroscopic hydrocarbon-polar medium interface, where preferential accumulation of the surfactant molecules occurs. The surfactant binding to the polymer is described by the multiple equilibria model commonly used to describe the protein-ligand interactions.