Oil-water pipe flow experiments in a horizontal and slightly inclined test section are presented. The experimental work was performed in a 16 m acrylic test section with ID of 60 mm, using tap water and a medium viscosity oil (61 cP) as test fluids. The pipe inclination was gradually changed from −5° to +5°. In-put water cuts from 0 % to 100 % were covered. The mixing velocity was varied from 0.1 m/s to 1.0 m/s. Flow pattern maps, local phase fraction, and pressure gradient measurements are shown. Significant influence of the pipe inclination was found. This effect became more crucial as the mixing velocity was reduced. The experimental results are compared with low viscosity data from Kumara el al. (2) and the commercial flow simulator OLGA.


Pipelines in hilly terrain are a common scenario for offshore as well as onshore production systems. The inclination of a pipeline is a crucial factor considerably influencing the oil-water flow. Small deviations from horizontal alignment can cause large changes of the local phase fractions and consequently the pressure gradient. Available data is, however, often limited to low viscosity oils and small inclination angles. Furthermore, the tested flow velocities are a restriction in the available data. Common flow simulators are mainly developed based on low viscosity data. Predicting flow with high viscosity oil these simulators often do not give satisfying results. Further research on high viscosity fluids is needed.

Abduvayt et al. (1) found that slight changes in the angle of pipe inclination can cause significant changes in the local water fraction. The higher the upward inclinations, the larger the water fraction compared to horizontal alignment. An opposite effect was observed for the downward inclined pipe. A similar behavior was found by Kumara et al. (2); who performed similar experiments as presented in this study, while using a low viscosity oil (1.6 cP). Also Lum et al. (4, 5) studied oil-water flows with a low viscosity oil (5.5 cP) in a smaller pipe diameter (ID = 38 mm) and reported higher local water fraction in upward inclined pipes than horizontal pipe.

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