Molecular Structure: The First and Most Significant Factor in the Precipitation of Asphaltenes

For decades, asphaltene deposits have been one of the most common problems in the oil industry in production, transportation, refining, processes, and storage. To find a solution, researchers have always faced three intertwined challenges of accurate structure determination, properties investigation, and precipitation prediction because asphaltenes in one oil sample are “a spectrum of complex molecular structures with very close masses.” Various models and theories of the inherent self-association of asphaltenes have been presented. All of them confirm the role of the unique molecular structure of asphaltenes as “the initiator” of the precipitation process. The driving factor for self-association is π-π stacking of aromatic rings. Recent advances in molecular dynamics (MD) calculations confirm the results of recent models. After the molecular structure, thermodynamic parameters (P, T, and composition) are the influencing agents on precipitation. Any change in these parameters causes an increase or decrease in the intensity of the precipitation. Due to the greater importance of molecular structure over other parameters, until the great challenge of characterization of asphaltenes is not specific, the validation of sediment prediction models will undoubtedly be accompanied by errors. In this paper, we review essential types of asphaltene self-association models and precipitation prediction methods. As an introduction and emphasis on the understanding of this inherent phenomenon, the weight, molecular structures, analysis methods, and ambiguities are investigated.