Stability and Dispersion of Asphaltenes: Performance Comparison between Strongly and Weakly Interfacially Active Asphaltenes

Asphaltene is a significant cause of flow assurance problems in the petroleum industry. Asphaltene precipitation from crude oil due to changes in pressure, temperature and oil composition leads to deposition and fouling in wellbores and production facilities. Asphaltene is defined as the fraction of crude oil that is soluble in aromatic solvents and insoluble in alkane solvents. Asphaltene is composed of a variety of functional groups and compositions; this broad definition has limited mitigation efforts and laboratory examinations, preventing focus on the fraction of asphaltene that interacts at liquid/solid interfaces, stabilising water in oil emulsion and adsorbing at solid surfaces. The fractionation of asphaltene can help us to identify and understand the functional groups and molecular interactions of the most problematic asphaltene fractions. The extended-SARA (E-SARA) analysis is a great method for the fractionation of asphaltene based on adsorptive potential, allowing the most interfacially active asphaltene (IAA) to be separated from the bulk solution.

The chemical characterisation of fractionated asphaltene showed a difference in the content of both heteroatoms and functional groups. The measurements indicated an abundance of oxygen and sulphur in the IAA fraction, which were mainly present in the sulfoxide, sulfone and carbonyl groups. The IAA is highly enriched, with a polar functional group that contributes to its emulsion stability and strong intermolecular interactions. The characterisation revealed a difference between the fractionated asphaltenes, with IAA structures comprising smaller cores that are aryl-linked or linked by alkyl chains.