Molecular dynamics simulation of yield thixotropy of crude oil systems

Abstract

In the work, molecular dynamics simulation is employed to analyze the micro mechanism of the yield thixotropy of crude oil. The effects of different shear rates on the yield thixotropic characteristics of the crude oil systems are investigated based on the Shengli crude oil system and the Nanyang crude oil system. The yield thixotropic mechanism of the crude oil systems is revealed by analyzing the orientation of the crude oil molecules, the extension degree in the molecular chain of crude oil, and the energy of the system. The results show that at the beginning of shearing, the molecular chain of crude oil gradually curls to prevent the changes in molecular orientation, and then a small amount of distortion occurs and the shear stress gradually increases. In the process of shear failure, the number of trans configuration molecules gradually increases and the number of Ponzi configuration and homeopathic configuration molecules decreases. The molecular chain of the crude oil gradually extends and the crude oil molecules show a directional arrangement consistent with shear direction, and the shear stress decreases.