Application of Anion-Cation Pair Surfactant Systems to Achieve Ultra-Low Oil-Water Interfacial Tension

Abstract

In this paper, ultra-low interfacial tension was obtained in realistic oil-water systems using ion pair surfactant systems. To improve the solubility of the ion pair surfactants, polyoxyethylene chain was introduced into the anionic surfactant molecular structure, and a three-component strategy where ion pair surfactants were combined with a non-ionic surfactant was used. Furthermore, the effects of the structures of the cationic and non-ionic surfactants, distribution ratio of the three components, and surfactant concentration on oil-water interfacial tension were studied. We successfully achieved the ultra-low interfacial tension in the Shengli oil fields using the mixed systems combining ion pairs and non-ionic agents. Several systems possessed an interfacial tension as low as 10 mN·m-1. Because of the strong electrostatic attraction between surfactant ions, our systems possess ultra-low interfacial tension after adsorption. The results show that after 48 h quartz adsorption, the systems can still reduce the interfacial tension to an ultra-low level.