Molecular dynamics simulation ongelation process of waxy crude oil

Abstract

Gelation of waxy crude oil is the source of its complex macroscopic rheological properties, while the rheological properties of waxy crude oil are the important basic data for pipeline transportation.Herein, two models of waxy crude oil system were established based on the macroscopic experimental data, and the molecular dynamics simulation was carried out using the Materials Studio software. In this way, the microscopic mechanism for gelation process of waxy crude oil was studied from the prospective of molecular dynamics. According to the results, the simulated condensation point value of crude oil is consistent with the experimental value through the judgment based on the density and diffusion coefficient. The sudden change of diffusion coefficient of wax crystal molecules and the deviation of mean square displacement are significantly reduced due to the formation of spatial network structure during crude oil gelation. By characterizing the change of microstructure of crude oil during gelationwith the radial distribution function, it is found that the peak value of radial distribution function between the same types of molecular increases gradually, and the largest degree of aggregation between wax crystals occurs at the condensation point. So, wax crystal molecule is the main factor that affects the condensation point of waxy crude oil. Generally, the research resultscouldprovide a basic theory for the acquisition of basic data concerning the pipeline transportation technology of waxy crude oil.

Keywords

• waxy crude oil
• molecular dynamics
• gelation
• condensation point
• microscopic mechanism