Determination of Multiphase Boundaries for Pressure–Temperature (P–T) and Enthalpy–Temperature (H–T) Phase Diagrams of C3H8/CO2/Water/Heavy Oil Systems at High Pressures and Elevated Temperatures

Abstract

In this study, techniques have been developed to determine multiphase boundaries of C3H8/CO2/water/heavy oil systems in both the pressure-temperature (P-T) and enthalpy- temperature (H-T) phase diagrams, respectively. Experimentally, the upper three-phase boundary pressures (i.e., saturation pressures) between aqueous/liquid/vapour (ALV) and AL phases are measured for three C3H8/CO2/water/heavy oil mixtures. Moreover, the fluid samples in both L and V phases are collected to conduct compositional analysis by using the gas chromatography (GC) method. Theoretically, the previously developed water-associated model, which considers only the presence of solvent with high solubility in water, together with the new alpha functions tailored for water and non-water components are employed to predict the multiphase boundaries of the aforementioned systems. A newly developed enthalpy determination algorithm is applied to calculate enthalpy of the Lloydminster heavy oil. The recently proposed water-associated model i...