When metering multiphase mixtures of produced hydrocarbon fluids one of the important characteristics is the flow pattern. Generally produced hydrocarbon fluid streams consist of oil and gas phases together with the presence of water; this additional liquid phase can have a significant influence on the variety of flow patterns which may be generated, the transitions between them, and the bulk properties of the flow. A considerable body of experimental research data and physical models exists for two-phase flows of gas and liquid, but to date there has been a notable lack of similar studies for three-phase oil/water/gas flows; those studies that are available have been difficult to piece together into useful methods for predicting the behaviour in a more general situation. An experimental programme has been undertaken at the National Engineering Laboratory to collect data for three-phase flows of oil, water and gas within both 4-inch and 6-inch pipelines over a wide range of flowing conditions. The National Multiphase Flow Calibration facility at NEL has been constructed to provide metered flows of nitrogen, water and crude oil for the evaluation and calibration of multiphase flow meters. For the experiments described here the facility was set up with horizontal pipelines of 60 metres in length and 4-inch and 6-inch internal diameter. The pipelines included Perspex visualisation sections to allow observation of flow patterns. All the recognised two-phase flow patterns for horizontal pipes were observed (stratified, slug, annular and bubble flows, and transition regions between these flows) together with a number of additional flow patterns effects specific to three-phase flows. The three-phase flow effects arise from the different distributions of the oil and water phases which can occur, for example stratified or slug flows with separate oil and water layers or with dispersed oil and water phases.
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