Development of predictive molecular models to describe thermodynamic and transport properties of hydrocarbons and their mixtures present in petroleum fractions

One of the remaining challenges in the oil industry is the lack of applied modeling tools capable to provide accurate information on the thermodynamic and transport properties of fluids in a consistent framework. While numerous correlations and equations are available in process simulators, they can lead to inconsistencies when used separately to describe a whole set of properties of multicomponent mixtures, particularly at high pressure conditions. The goal of this contribution is to overcome this issue by presenting a molecular-based equation of state, named soft-SAFT, to simultaneously describe thermodynamic and transport properties of oil-related systems. The equation presented is based on statistical mechanics and has been extended to calculate transport properties by adding different the Free-Volume Theory, relating all the different properties in a consistent manner. This allows an accurate evaluation of density, phase equilibria and viscosity of fluids and mixtures in a wide range of conditions. The formulation includes a series of molecular parameters that are related to the chemical structures and the molecular weight of each compound, allowing the possibility of extrapolating at different working conditions, as well as describing similar molecules when experimental data are not available. With this integrated approach, all the data is consistent and there is no need to use additional independent correlations.