P-μ-T cubic equation of viscosity for hydrocarbons

Abstract

Viscosity model is important for the simulation of flow and recovery behaviour of different hydrocarbon systems. Various semi-theoretical models such as Friction-Theory and cubic Equation of State-based models have been found satisfactory for lighter crudes. However, for heavier hydrocarbon systems e.g. heavy oils, bitumens, these models are not reliable; one possible reason is that they are not reliable for heavier components. The objective of this research is to develop a viscosity model sensitive to molar mass and density of components and a mixture of hydrocarbons.In this work, a Cubic Equation of Viscosity model where P-ρ-T form of cubic equation (Abbott, 1973) is converted into P-μ-T form of cubic equation, is developed with desired sensitivity to density and molar mass. The model requires three parameters, which are optimized by viscosity data matching. Separate sets of parameters are developed for hydrocarbon groups such as paraffins, naphthenes, and aromatics. Viscosity estimation for mixture requires mixing of the parameters and not the viscosity values of individual components.The carbon number of heaviest component used in the model is 64. The P-μ-T viscosity model has AARD of 2.91%, 3.06% and 5.68% for paraffins, naphthenes, and aromatics respectively in comparison of 33.95%, 19.6%, and 48.9% from T-μ-P (Guo et al., 2001) model. Friction Theory (Quinones-Cisneros et al., 2000) based model results in 26.38% AARD for paraffins. For 19 paraffinic mixtures, AARD from P-μ-T is 5.56% in comparison to 29% from T-μ-P (Guo et al., 2001) model and 316% from Friction Theory (Quinones-cisneros et al., 2000) model.