Viscosity is an important transport property for engineering design and simulation of bitumen production and transportation. During the production of bitumen with solvent injection, steam-assisted gravity drainage (SAGD) or expanding solvent steam-assisted gravity drainage (ES-SAGD), the produced fluid is faced with various temperature, pressure and composition conditions. Therefore, a model is necessary to predict the viscosity of the mixture of bitumen and solvent in wide ranges of temperatures, pressures and compositions (T-P-x).

In this work, we propose a semi-theoretical viscosity model based on the Arrhenius mixing rule and considering the effect of association between the molecules of the solvent and the bitumen. To achieve this purpose, thermodynamic perturbation theory (TPT) is used. The association part of the cubic-plus-association (CPA) equation of state (EoS) is applied to calculate the fraction of bonding solvent molecules. We calculate the viscosity of the solvent in wide temperature and pressure ranges using the modified Enskog theory (MET).

Results show an acceptable agreement between the results of this model and experimental viscosity data of saturated bitumen with different solvents (CH4, N2, CO2, and C2H) at various T-P-x ranges. These experimental data cover the typical T-P-x ranges of oil recovery methods.

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