Phase Transitions and Separation Time Scales of CO2-Crude Oil Fluid Systems: Wheel Flow Loop Experiments and Modelling

Abstract

Presented here is experimental and theoretical work on phase transitions and separation time scales for CO2−crude oil mixtures with CO2 content ranging from pure to 79 mol %. The experimental work was performed using the wheel flow loop located at the SINTEF Multiphase Flow Laboratory. Under constant volume conditions, phase transition temperature and pressures were determined, as well as the volume fractions of the respective phases. The results indicated good agreement between the experimentally determined phase transitions and the phase diagrams predicted by the thermodynamic model. It was shown that the measured torque was sufficient to determine the pressure−temperature conditions of the phase transitions. Furthermore, separation times were measured for both oil-in-CO2 and CO2-in-oil in a range of conditions for the respective fluid systems. Results showed that the separation times were considerably shorter for the CO2 continuous fluid system compared to oil continuous. Moreover, a comparison of Weber numbers for the various test conditions indicated that the drop sizes influence the overall separation time, which is affected by settling and coalescence processes. Finally, this study showed that the wheel flow loop is well suited for the study of CO2-rich systems for determination of volume fractions of phases, phase transitions, and transport and separation