Asphaltenes:: Structural characterization, self-association, and stability behavior

The influence of different factors on the asphaltene stability in four crude oils was evaluated. Compositional studies and structural characterization of resins and asphaltenes were carried out in order to study a possible relationship between these properties and the asphaltene deposition behavior. Low hydrogen-to-carbon ratios, high aromaticities, and high condensation of aromatic rings were the main characteristics of the asphaltenes from unstable crude oils. According to these results, the stability behavior of the crude oils studied was strongly influenced by the structural characteristics of their asphaltenes, Since the self-aggregation of asphaltenes is a first step in the formation of precipitated asphaltene particles, this study also evaluates the formation of asphaltene aggregates as a function of the structural characteristics of the asphaltenes. The self-aggregation behavior was studied on the basis of surface tension measurements. Critical micelle concentrations were determined in different solvents. Using these results, it was possible to establish a relationship between self-association and structural characteristics through the calculation of the Flory parameter. On the basis of these findings, different characteristic patterns were identified depending on the origin of the asphaltenes. A new correlation has been found to describe the critical micelle concentrations of the asphaltene solutions.