Flow structure and phase distribution in stratified and slug flows measured by X-ray tomography.

Flow structures and phase distributions in two- and three-phase stratified and slug flows were studied with a fast-response X-ray tomography system. A large number of experiments were carried out in a 25 m long near-horizontal pipeline with an internal diameter of 100 mm. A dense gas, SF 6 , was used to simulate the gas phase in high-pressure gas-condensate pipelines. Detailed measurements of the flow were made with the X-ray system at various superficial velocities, two different pressures (4 and 7.2 bara, giving gas densities of 24 and 42 kg/m 3 , respectively), and three different inclination angles: 0, +1 and +5 degrees. Both qualitative observations and quantitative measurements were obtained which illustrate the different types of interface structure and fluid flow behaviour. The detailed measurements have also been used to obtain a more reliable correlation for predicting the fraction of gas bubbles entrained in the liquid layer in turbulent stratified gas–liquid flows. The measurements in three-phase slug flows reveal interesting phenomena regarding the interactions of the oil–water and gas–oil interfaces. Depending on the flow conditions, the oil–water interface can sometimes decouple from the gas–liquid interface, leading to oil-dominated slugs flowing on top of a water layer of nearly constant thickness. [ABSTRACT FROM AUTHOR]