Influence of Crude Oil Fractions on Interfacial Tensions of Alkylbenzene Sulfonate Solutions

The influences of crude oil fractions, such as acidic fractions, resins, and asphaltenes, on the interfacial tensions (IFTs) of kerosene against surfactant mixtures with different hydrophilic–lipophilic ability were studied by a spinning-drop interface tensiometer in the present work. The IFTs of crude oil, diluted crude oil, and treated crude oil by formation water against surfactant mixtures have also been investigated. The results show that a small quantity of acidic fractions will reduce the equivalent alkane carbon number (EACN) values of model oils and result in the slightly decrease of IFTs for surfactant solutions with higher water solubility. On the other hand, the superfluous addition of acidic fractions could obviously increase the IFT mainly because of the mixed adsorption of acidic fractions and surfactant molecules. The resin shows almost the same trend of effecting IFTs as acidic fractions because most acidic fractions with high surface activity distribute over resin fractions. However, the asphaltene shows a weak tendency of forming mixed adsorption films because of low surface activity and large molecular size. Therefore, asphaltene has little effect on the ultralow IFTs between surfactant solutions and kerosene. The experimental results of treated crude oil by weak alkaline and diluted crude oil by dodecane further verify that the mixed adsorption of petroleum acids hinders the production of ultralow IFT.