Effects of high oil viscosity on slug liquid holdup in horizontal pipes

In the recent years, the increased consumption of hydrocarbon resources and the decline in discoveries of low viscosity oils increased the importance of high viscosity oils. Significant changes in flow behavior were observed with increasing oil viscosity. Determination of the liquid holdup in the slug body is essential to calculate pressure drop for multiphase flow systems. An experimental study was performed to investigate the effect of high oil viscosity on slug liquid holdup and liquid film height. 144 tests were carried out in 50.8-mm ID horizontal pipe for different oil viscosities and superficial liquid and gas velocities. Tests were conducted at oil viscosities of 0.587, 0.378, 0.257 and 0.181 Pas. Superficial liquid and gas velocities varied from 0.1 to 0.8 m/s and 0.1 to 3.5 m/s, respectively. The experimental measurements were compared with the existing slug liquid holdup model predictions to investigate the performances of these models for high viscosity oil. The predictions of the Gregory et al. (1978), the Gomez et al. (2000), the Abdul-Majeed (2000), the Al-safran (2009) correlations and the Zhang et al. (2003) mechanistic model were compared with high viscosity data. It was concluded that the slug liquid holdup predictions of these empirical and mechanistic models disagree with measurements especially above a 2 m/s mixture velocity. New slug liquid holdup correlations were developed in this study. The new correlations are expected to improve predictions of slug liquid holdup for high viscosity oil especially at high mixture velocities. No significant effect of high oil viscosity on liquid film holdup was observed within the selected oil viscosity range of this study.