Deepwater production offers many challenges to oil & gas companies. The challenges are mainly due to operations at ultra low temperatures, high pressures, long pipelines and transporting multiphase phase flows. From purely transport point of view, there is clear need to better understand the multiphase flows in these pipelines. The multiphase flows in these pipelines are characterized by flow patterns or regimes that define a particular distribution of liquid and gas volume fraction in the pipeline. Pressure drop and other transport characteristics such as mass and heat transfer are closely related to the flow patterns or regimes. Thus the flow regime prediction is an important and vital step in understanding the multiphase flows. Untill now most of the numerical multiphase models that are used in design also require apriori knowledge of the flow regimes.

Typically flow regime maps are used and these are dimensionless and should be applicable to wide variety of flow scenarios (fluid properties and pipe sizes). However recent experiments have suggested that flow patterns and other parameters are different in small and large pipes. In this paper, we used a CFD based model in understanding and prediction of bubbly flow, slug-flow/intermittent, semi-annular and annular-flow of vertical pipeline. The CFD model uses Eulerian-Eulerian Multifluid VOF approach to model all the flow regimes, as it allows selective use of surface tension and interface sharpening schemes in an Eulerian framework. Gas holdup, pressure drop and flow instabilities will be predicted and compared with available data for different flow regimes. The predicted results shows good agreement with the experimental work and clearly highlight application of CFD modeling to predict the flow regimes and to get better understanding of complex flow behavior in gas-liquid vertical flows.

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