Phase equilibria of waxy live oil systems containing CO₂: Experimental measurements and thermodynamic modeling

In this work, accurate experimental measurements of phase equilibrium data over a wide range of temperature and pressure were carried out for several synthetic live oil systems containing mixtures of hydrocarbons and CO₂ employing an exponential decay in composition. The apparatus used in this study to measure the wax disappearance temperature (WDT) of the live oil systems consisted of a constant-volume visual cell rocking rig equipped with sapphire windows connected to a thermostatic bath with digital control. The data obtained were used to assess the predictive capability of existing phase equilibrium thermodynamic models: the Peng−Robinson equation of state incorporating a group contribution method to calculate binary interaction parameters for fluid phase description and three different activity coefficient models for wax phase. Also, phase equilibrium data gathered from the literature were modeled while results from five high-pressure correction methods were compared. The modeled results showed good predictability against the independent experimental data, demonstrating the robustness of the experimental procedure in this study.