Modelling Viscosity based on a Molecular Description

In this paper, we illustrate that the modern trends for viscosity prediction are moving away from empirically based methods to those that make use of a sound theoretical framework and are validated against primary experimental data. The Vesovic-Wakeham (VW) method is in the forefront of these developments. It is founded on the kinetic theory of hard-sphere fluids that is appropriately modified to take into account the behaviour of real fluids. It makes use of mixing rules that are thermodynamically consistent and more importantly have no adjustable parameters. In this work the VW model has been used to predict the viscosity of reservoir fluids that are of interest to the oil and gas industry. In particular, we examined the predictive capabilities of VW model by comparing against accurate experimental data on natural gas and liquid alkane mixtures that form the main constitutes of oil. The natural gas data were reproduced with uncertainty of better than 1%, while the viscosities of liquid alkane mixtures were reproduced with the uncertainty of 4%.