Aggregate Structure in Heavy Crude Oil: Using a Dissipative Particle Dynamics Based Mesoscale Platform

Abstract

Heavy crude oil consists of thousands of compounds and much of them have a fairly large relative molar mass and complex structure. It is hard to learn the dynamic behavior of this fluid system at all atom models. The present study aims at constructing a mesoscale platform to explore aggregate behavior of asphaltenes in heavy crude oil. The aggregate structure in heavy crude oils was investigated by introducing rigid body fragments, which represents the significant presence of structures of fused aromatic rings in fractions such as asphaltenes and resins into dissipative particle dynamics (DPD). Another pressing task about how to determine the structure of the average model molecules and conservative force parameters was discussed in detail. With some regularity concerning the number of rings, the distribution of side chains and heteroatoms in average model molecules are revealed. Finally, we integrated the modified DPD program, model molecules, and the parameters selected for the preliminarily simulation of the heavy crude oil and emulsion system. The interlayer distance and the number of layers of the well-ordered structure in heavy crude oil are similar to some molecular dynamics works and supported by X-ray and transmission electron microscopy (TEM) experimental data. The relationship between the stability and the mass ratio among components of heavy crude oil is explored, and the result of our simulations fits the regularity <i>Shell</i> once published. In the emulsion system, the surfactant-like feature of asphaltenes and resins are observed. The preliminary simulation results demonstrate the validity of the rotational algorithm and parameters employed and encourage us to extend this platform to study the rheological and colloidal characteristics of heavy crude oils in the future