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

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.

Combined Approach to Evaluate Hydrate Slurry Transport Properties through Wetting and Flow Experiments

“…In light of the challenges of the Vega asset, described below, the objective of the current work was to experimentally evaluate alternative flow assurance approaches for the gas condensate system utilizing the wetting index method and a wheel flow loop as described elsewhere in the literature. ,, AAs are designed to render the gas hydrate particles oil-wet when formed, thus avoiding agglomeration and plugging. ,, We present in this work experimental data on the wettability and transportability of the Vega fluid under different conditions, namely, uninhibited, underinhibited (10% MEG), and with an AA present. The results from the experiments are further discussed in the context of a potential field application in Vega assets and in gas condensate fields in general.…”