The corresponding states viscosity model applied to heavy oil systems

The corresponding states viscosity model is widely accepted in the petroleum industry for calculating oil and gas viscosities. In its classical form, the model predicts the viscosities of complex mixtures using methane as a reference compound. As a result of the chosen reference compound, the corresponding states model has good predictive capabilities for gases and light oil systems, whereas the predictive performance deteriorates for heavier oil systems. The present work discusses how far the performance of the corresponding states models can be stretched in its classical form with methane as the reference compound. It further outlines a procedures based on a viscosity correlation for stable oil mixtures that may take over when the methane reference temperature becomes too low to apply methane as reference compound. In the temperature region where the new correlation is to take over from the classical corresponding states model, there is a smooth transition between the viscosity results obtained with either method. Therefore, the new correlation can be seen as an extrapolation of the corresponding states method to be applicable to heavy aromatic oil mixtures at relatively low temperature.