Mechanism Analysis of Heavy Oil Viscosity Reduction by Ultrasound and Viscosity Reducers Based on Molecular Dynamics Simulation

Ultrasound and viscosity reducers are commonly used methods to reduce the viscosity of heavy oil. In order to compare the viscosity reduction effects of ultrasound and viscosity reducers and study their mechanism of interaction on heavy oil, molecular dynamics simulation was carried out in this paper. First, a molecular model of heavy oil composed of asphaltene, resin, aromatic hydrocarbon, and saturated hydrocarbon was established in this work. Through molecular dynamics simulation, the different effects of ultrasound and viscosity reducers on the viscosity reduction rate, hydrogen bond number, hydrogen bond type, and occupation rate were obtained, and the viscosity reduction mechanism of ultrasound and viscosity reducers was analyzed. By calculating the viscosity reduction rate and the number of hydrogen bonds of five oil-soluble viscosity reducers with or without ultrasound, it was found that the types of hydrogen bonds affecting the viscosity reduction effect were different with or without ultrasound or viscosity reducer, and the type and content of viscosity reducer would affect the effect of ultrasonic viscosity reduction. The amplitude, frequency, and temperature of ultrasound were also the factors affecting the effect of viscosity reducers. The simulation results helped to explain the mechanism of jointly reducing the viscosity of heavy oil by ultrasound and viscosity reducers from the microscopic point of view and provided a theoretical basis for the industrial application of ultrasound and viscosity reducers to reduce the viscosity of heavy oil.