Technical Paper: Understanding Heavy Oil Molecular Functionality and Relations to Fluid Properties

Society: World Heavy Oil Congress
Paper Number: 11-612
Presentation Date: 2011


Often viscosity is mentioned as the single most important physic chemical fluid property of heavy oil in terms of production. Viscosity, adherence to reservoir rock, water emulsification (amongst others) have all been known for decades to be related to the presence of nitrogen, sulfur, oxygen and heavy metals (NSO) components. In the thermodynamic modeling of phase behavior and property prediction NSOs have a major impact on, for example, critical properties but the actual impact is often omitted. These constituents interact via functional groups and specific interactions with other molecules. In heavy oil where more than 50% of the oil cannot be distilled, the separation, identification and quantification of these compounds become difficult or impossible. Often one will observe that hydrocarbon structure is discussed in detail (e.g., asphaltene structures) while NSOs are discussed in general terms. Specific chemical reactions or additives with specific interactions reveal how 3D structural networks can be broken to diminish molecular interactions and thereby, for example, viscosity. The paper will review work done using asphaltenes altered by “chemical surgery” removing specific functional interactions applying techniques such as titration calorimetry and fluorescence spectroscopy combined with data on effect of additive solvents on viscosity, and place this in the context of understanding heavy oils and fractions of petroleum. This will show how determination of specific interactions (functional groups) may be very useful indeed and even more important than understanding hydrocarbon structures in heavy fractions.

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