Enhanced oil recovery by sacrificing polyelectrolyte to reduce surfactant adsorption: A classical density functional theory study

Abstract

During the process of chemical enhanced oil recovery (CEOR), surfactants are widely used as they can reduce interfacial tension and change surface wettability, but the huge economic losses caused by the adsorption of surfactants on rock surface need to be resolved. Therefore, polyelectrolyte is introduced to reduce the adsorption amount of surfactant. However, how to select appropriate polyelectrolyte suitable for different reservoirs is always lack of theoretical guidance. Herein, the competitive adsorption mechanism between surfactant and polyelectrolyte on rock surface is studied by classical density functional theory (CDFT). Having investigated the effects of different polyelectrolytes on the adsorption of surfactants, the optimal polyelectrolyte concentration and chain length suitable for different potentials were found. Also, the influence of rock crevices width on displacement effect was considered. Moreover, we proposed a comprehensive evaluation of polyelectrolytes in terms of both the performance and economy. The findings of this study benefit for further understanding of the competitive adsorption in CEOR, and provide guidance for the practical application of polyelectrolytes.