Mechanistic Models for Three-Phase Stratified and Slug Flows with Dispersions

A large research programme has been carried out to develop new mechanistic models for gas-oil-water multiphase flow in gas condensate and light oil systems. The emphasis has been on mechanistic models that have the correct scale-up behaviour with pipe diameter and fluid properties (especially gas density). This is essential in order to reduce uncertainty associated with fluid properties and pipeline sizes that differ greatly from available experimental data. For gas condensate systems, the main research topics have been 3D "pre-integrated" three-phase stratified flow models, improved turbulence closures, and dispersion models for transport of drops and bubbles. These are essential for prediction of the onset of liquid accumulation in gas condensate pipelines. For light oil systems, the main research topics have been dynamic slug flow models including gas entrainment, oil-water dispersions, slug body friction and slug frequency based on mechanistic models. Improved models for three-phase slug birth and death rates are essential for the prediction of slug development in undulating pipelines. The paper discusses the underlying modelling principles and presents some highlights.