Microscopic behavior of heteroatom asphaltene in the multi-media model: The effect on heavy oil properties

Abstract

The high viscosity and surface adsorption of heavy oil pose significant challenges for its exploration. Asphaltenes, the most polar and heaviest components of crude oil, play a crucial role in these properties. Heteroatom asphaltenes (A-X, S-Y) exhibit stronger interaction energy compared to non-heteroatom asphaltenes A-C. The self-assembly of A-X/S-Y forms ordered "reinforcement-cement" aggregates, whereas A-C aggregates are more chaotic. The presence of heteroatoms, particularly the sulfur atom in the side chains, may significantly influences asphaltene aggregation structures. The diffusion coefficient of heteroatom asphaltene in oil droplet is smaller than that of A-C, and these heteroatom compound can bind other oil components, reducing the overall fluidity. Notably, the adsorption energy of asphaltenes on solid surfaces exceeds their interaction energy. Surface aggregation of A-X/S-Y is more dispersed compared to A-C adsorption system. Additionally, the existence of heteroatom asphaltenes can shorten the distance between oil droplets and the solid surface by 16.20 Å compared with non-heteroatom system. These phenomena, caused by A-X/S-Y, further complicate the detachment of crude oil components from surfaces. This study aims to share some new insights into the micro-mechanisms of heteroatom asphaltenes self-assembly and the behavior in the oil-sludge process, which may contribute to the theoretical foundation for the targeted and efficient exploitation of heavy oil.