Viscosity modeling of reservoir fluids using the Friction Theory with PC-SAFT crude oil characterization

The Friction Theory (FT) for viscosity modeling is applied to a characterization method based on the Saturates-Aromatics-Resins-Asphaltenes content (SARA) which makes use of the Perturbed-Chain version of the Statistical Associating Fluid Theory equation of state (PC-SAFT EoS). The viscosity modeling results are compared to Chi-Square (CS) characterization method that uses Peng-Robinson (PR) EoS. In the Friction Theory, viscosity is calculated using repulsive and attractive pressures from an EoS. In this work, the FT parameters for pseudo-components are obtained by tuning to a single value of viscosity at saturation condition. A new fitting approach for PC-SAFT FT model is proposed where the number of fitting parameters for each pseudo-component is reduced from two to one. The simulation results for 10 light crude oils from the Middle East region show that using PC-SAFT EoS to represent the phase behavior of the crude oil provides viscosity predictions that are at least as good as the CS method that uses PR EoS, even though a lower number of tuning parameters and pseudo-fractions are used. However, the use of PC-SAFT to calculate repulsive and attractive pressures in the FT model does not significantly improve the accuracy in viscosity modeling as compared to the use of PR EoS.