Formation and characterization of petroleum asphaltene aggregates: a review

Asphaltenes comprise the most structurally complex fraction of crude oil and critically influence petroleum processing, transportation, and refining operations. The discussion on asphaltene molecular architecture is essential for predicting behavior such as aggregation, deposition, and interactions with solvents. Although considerable research has been conducted over the past five decades, a comprehensive and universally applicable theory describing the mechanisms of heavy organic precipitation and deposition in crude oils, irrespective of their geological origin, has not yet been fully established. Nonetheless, several predictive models have been developed that provide satisfactory descriptions under specific conditions. These models generally treat heavy organic constituents, particularly asphaltenes and resins, as existing in crude oil either in a molecularly dissolved state or as colloidal particles dispersed and stabilized by the adsorption of resin molecules on their surfaces. This work also evaluates current analytical approaches for asphaltene characterization, primarily Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), and mass spectrometry (MS), to understand the formation of aggregates. The critical discussion of analytical techniques identifies their respective strengths, limitations, and synergistic potential for comprehensive asphaltene characterization. The debate highlights gaps in current methodologies. A straightforward integration of microscopic-level molecular insights with macroscopic flow assurance challenges is sought. Future progress will depend on coupling molecular-level characterization with predictive thermodynamic models to anticipate precipitation onset and guide the design of more effective mitigation strategies in reservoir and production systems.