Some Compositional Viscosity Correlations for Crude Oils from Russia and Norway

The current work is based on experimental viscosity and compositional data of about 200 crude oil samples from various parts of Russia and the Norwegian continental shelf. Data analyses were performed to estimate correlations between viscosity and density values as well as concentrations of main components from the crude oils of different origins. It appeared that, in some cases, it is possible to establish a general correlation of viscosity increase along with growing asphaltene, resin, and aromatics contents but also a decrease in viscosity with increasing saturates content. The spread of the data points can be rather wide for the oils of different origins. It was observed that asphaltenes from all of the crude oil samples acted as promoters of the viscosity growth at rather low concentrations, while resins and aromatics effectively increased viscosity in a higher concentration range. The effect of asphaltenes on the viscosity of real crude oils seems to be more important than when dissolved in a model solvent (xylene). This means that either the asphaltenes have a different solvation state in crude oils compared to xylene or asphaltenes are not solely responsible for the high viscosity of the crude oils.