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

Abstract

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.

Aquathermolysis of Heavy Crude Oil: Comparison Study of the Performance of Ni(CH3COO)2 and Zn(CH3COO)2 Water-Soluble Catalysts

“…It is well-known that a small decrease in the content of the asphaltenes of oil can significantly reduce the viscosity of it. Even the changes in the molecular shape or conformation can alter the viscosity of heavy oil [41][42][43]. The results of viscosity measurements are illustrated in Figure 2.…”

Real-time online monitoring technology for sweeping frequency ultrasound (SFU) assisted extraction of amur grape (Vitis amurensis) seed oil

“…In addition, the oil viscosity by SFU assisted extraction was significantly lower than that by the organic extraction. Within a certain period, the apparent viscosity of the oil was reduced by ultrasonic treatment [45] . This was because the greater the cavitation intensity, the more certain elements of oil were degraded by ultrasonic waves, resulting in a more significant decrement of apparent viscosity.…”

Pathway of Oil-Soluble Additives to Reduce Heavy Crude Oil Viscosity Depends on the Molecular Characteristics of Asphaltene

“…In the MD simulation work of Xu et al, 24 it was revealed that the oil-soluble VRs induce the transformation from face-to-face stacking of asphaltenes to face-to-face stacking of asphaltenes and resins, which was considered as the mechanism of reducing heavy oil viscosity. Zhang et al 25 explored the effect of oil-soluble VRs along with ultrasound, demonstrating that the type and content of VRs influence the ultrasonic viscosity reduction effect.…”

“…To provide insights into microscopic interactions between different heavy oil components and VRs, which are difficult to obtain from experiments, computational methods including quantum mechanics (QM) calculations and molecular dynamics (MD) simulations have been employed to explore dynamics and thermodynamics in heavy oil systems. Based on this, the molecular mechanisms of water-soluble VRs ,, and oil-soluble VRs , have been studied. In the MD simulation work of Xu et al, it was revealed that the oil-soluble VRs induce the transformation from face-to-face stacking of asphaltenes to face-to-face stacking of asphaltenes and resins, which was considered as the mechanism of reducing heavy oil viscosity.…”