Determination of Three-Phase Boundaries of Solvent(s)–CO2–Heavy Oil Systems under Reservoir Conditions

The liquid–liquid–vapor (L 1 L 2 V) phase boundaries of solvent(s)–CO 2 –heavy oil systems under reservoir conditions are experimentally and theoretically determined. Experimentally, the L 1 L 2 V phase boundaries of one CO 2 –heavy oil mixture, one C 3 H 8 –CO 2 –heavy oil mixture, and one n -C 4 H 10 –CO 2 –heavy oil mixture in the pressure–temperature ( P – T ) diagram are determined using a versatile pressure–volume–temperature ( PVT ) setup. The addition of an alkane solvent to the CO 2 –heavy oil system tends to expand the pressure and temperature span of the L 1 L 2 V phase boundary, while the L 1 L 2 V phase boundary of the solvent(s)–CO 2 –heavy oil system shows its tendency to move toward the high-temperature and low-pressure region of the P – T diagram. Theoretically, the previously developed binary interaction parameter (BIP) correlations for CO 2 –heavy oil binary, C 3 H 8 –heavy oil binary, and n -C 4 H 10 –heavy oil binary are incorporated into the Peng–Robinson equation of state (PR EOS) to determine the three-phase boundaries of the above-mentioned systems. The PR EOS with a modified α function and the BIP correlations is found to provide a generally good prediction of the experimentally measured L 1 L 2 V phase boundaries of the solvent(s)–CO 2 –heavy oil systems under reservoir conditions.