Readily accessible reserves of light crude oil are declining and attention is being focused on the extraction and upgrading of viscous tar sands, bitumens and heavy oils. In naturally occurring formations these oils are produced with up to 80% solids (sand) and formation (salt) water. Inevitably during the production process emulsions are formed, the emulsifier being provided from the natural surface active components of the oil. Relatively, very little is known about the chemical structure of these emulsifiers with, as a consequence, little detailed understanding of the mechanisms involved in emulsion formation and emulsion breakdown.Dilute solution viscometry is a powerful tool that provides information about molecular volume (intrinsic viscosity) and therefore, with suitable assumptions, molecular weight. Using polyisobutylene as a reference we demonstrate that the concentration dependence of viscosity of bitumen closely mirrors the concentration dependence of viscosity of different molecular weight fractions of PIB. The intrinsic viscosity of bitumen is much lower than that of the lowest molecular weight PIB, and indicates a molecular mass of approximately twenty five benzene equivelents.We present evidence that mixing bitumen with suitable demulsifiers produces an increase in molecular volume. Fractions from the bitumen, - of asphaltene and maltene produce smaller increases (or no increase) in volume, suggesting that components from both fractions play a role in the observed interactions.
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