Mechanistic Study of the Effects of Surfactants and Asphaltenes on the Action of Emulsions with Different Water Contents: Based on Dissipative Particle Dynamics

Abstract

Surface-active substances have an important influence on the performance of emulsions during crude oil production and processing. The mechanism of action of surface-active substances in emulsions with high and low water contents was investigated. The conformational changes of emulsions at different water contents in relation to the behavior of surfactant and asphaltene molecules in the system as well as the energy changes of the system were investigated from a microscopic point of view by using the dissipative particle dynamics (DPD) method. Through the analysis of DPD simulation snapshots and relative concentration distributions, it was found that there were differences in the effects of different surfactants on the conformation of oil–water emulsions at high and low water contents. Synergistic or competitive adsorption of asphaltenes and surfactants in the system affects the conformation of the emulsion. The change in the emulsion conformation in the compounding system is accompanied by the change in system energy. Based on the analysis of the radial distribution function and system energy, it was found that the intermolecular interactions between asphaltenes and surfactants in the complexed system were related to the change in system internal energy. The analysis of the radius of gyration shows that the water content of the system and the change in the complexing system will have different effects on the flexibility of the surfactant molecules in the system.