Our current understanding of water-in-crude oil emulsions. - Recent characterization techniques and high pressure performance

Hydroprocessing of Heavy Oils and Residua

Interfacial shear rheology of asphaltenes at oil–water interface and its relation to emulsion stability: Influence of concentration, solvent aromaticity and nonionic surfactant

In petroleum science, the term resin generally implies material that has been eluted from various solid adsorbents, whereas the term maltenes (or petrolenes) indicates a mixture of the resins and oils obtained as filtrates from the asphaltene precipitation. Thus, after the asphaltenes are precipitated, adsorbents are added to the n-pentane solutions of the resins and oils, by which process the resins are adsorbed and subsequently recovered by the use of a more polar solvent, and the oils remain in solution. The resin fraction plays an important role in the stability of petroleum and prevents separation of the asphaltene constituents as a separate phase. Indeed, the absence of the resin fraction (produced by a variety of methods) from the maltenes influences the ability of the de-resined maltenes to accommodate the asphaltenes either in solution or as a stable part of a colloidal system. In spite of the fact that the resin fraction is extremely important to the stability of petroleum, there is surprisingly...

Petroleum Resins: Separation, Character, and Role in Petroleum

When asphaltenes adsorb at liquid interfaces, after the rapid initial diffusion step toward the interface, a long reorganization and a progressive building of multilayers occur. The reorganization is faster at oil–water interfaces than at air–oil interfaces, but the multilayer formation takes similar times. In the case of oil–water interfaces, the time scales are similar for different oils, but the variation with asphaltene concentration is qualitatively different: adsorption becomes faster with increasing concentrations for oils that are good asphaltene solvents and slower in the case of poor solvents. The presence of surfactant changes significantly the adsorption process.

Adsorption Kinetics of Asphaltenes at Liquid Interfaces

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 s...

J. Espidel

Papers

Asphaltenes: Structural Characterization, Self-Association, and Stability Behavior

Aggregation of asphaltenes in organic solvents using surface tension measurements

Asphaltene Stability in Crude Oils