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 CO 2 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.

In this study, new experimental data using a reliable approach are reported for solid-fluid phase equilibrium of ternary mixtures of Methane-Carbon-dioxide- n-Hexadecane for 30-73 mol% CO2 and pressures up to 24 MPa. The effect of varying CO2 composition on the overall phase transition of the systems were investigated. Three thermodynamic models were used to predict the liquid phase fugacity, this includes the Peng Robison equation of state (PR-EoS), Soave Redlich-Kwong equation of state (SRK-EoS) and the Cubic plus Association (CPA) equation of state with the classical mixing rule and a group contribution approach for calculating binary interaction parameters in all cases. To describe the wax (solid) phase, three activity coefficient models based on the solid solution theory were investigated: the predictive universal quasichemical activity coefficients (UNIQUAC), Universal quasi-chemical Functional Group activity coefficients (UNIFAC) and the predictive Wilson approach. The solid-fluid equilibria experimental data gathered in this experimental work including those from saturated and under-saturated conditions were used to check the reliability of the various phase equilibria thermodynamic models.