Molecular dynamics simulation of wax deposition in crude oil systems

Abstract

Molecular dynamics (MD) simulation was employed to analyze the effects of different wax contents and molecular chain lengths on the wax deposition behavior in crude oil systems and the mechanism. The results show that the wax deposition on the iron surface occurs via a three-layer adsorption process driven by van der Waals (vdW) forces. In addition, there are four important stages in the process of crude oil deposition on iron surfaces. The first stage involves the diffusion of crude oil molecules onto the iron surface, the second involves their adsorption onto the solid surface and parallel alignment with the surface, and the third and fourth stages involve the formation of floccules through intermolecular interactions and bridging between the deposited layer adsorbed on the solid surface and the crude oil system. For different wax contents and molecular chain lengths, the wax deposition process is similar to crude oil systems, and the thicknesses of the deposited layers on the iron surface were similar. The primary contribution to the interaction energy between crude oil molecules and the iron surfaces is from vdW effects. As the crude oil system's wax content and molecular chain length increase, the interactions between crude oil molecules and the iron surface are strengthened, and these interactions are further enhanced as more crude oil molecules accumulate in the deposited layer. The results of the study may provide theoretical support for an in-depth understanding of the wax deposition process.