Office of VP for Research
Asphaltenes, known as the "cholesterol of petroleum," are a problematic class of molecules found in crude oil with a propensity for aggregating and coating the surface of oil processing and transport equipment. These molecules are thought to form colloidal suspensions in oil that flocculate into viscoelastic masses when destabilized by a change in the processing conditions. These floccs are an expensive issue for the oil industry due to their ability to clog pipes and foul heat exchanging equipment.
Due to the difficulty in using experimental techniques to characterize molecule-level details of asphaltene behavior, molecular simulation is often used to study the behavior of proposed model asphaltenes. Most commonly, all-atom (AA) molecular dynamics is the methodology of choice for such simulation studies. At these low concentrations, the majority of the computation time is spent on simulating the solvent, as the solvent molecules greatly outnumber the asphaltenes. This limits the scope of feasible simulations to the nanosecond regime and precludes studies that require simulation at many state points. Coarse-grained (CG) modeling is one approach for extending the accessible scale of asphaltene simulations. CG models represent a target system at a reduced resolution by mapping out atoms from the all-atom model. This can provide a significant simulation speedup relative to an AA model, enabling larger scale simulation studies that can explore physically larger systems and/or multiple state points. This group uses an implicit solvent CG model to study asphaltene aggregation at the mesoscale level of aggregation, and under a variety of solvent qualities. This model captures the quality of the solvent for the model asphaltenes by scaling the attractive contribution to the nonbonded pair potentials.