A. General description of three-phase flows: Flow patterns

This section discusses three-phase flows comprising a gas phase and two liquid phases. More specifically, the important case of gas, oil and water is described. Such flows relate to both gas-liquid and oil-water flows since these are limiting cases of the more-general three-phase flow. However, the inclusion of the third phase leads to a further degree of freedom and the interactions between the phases, already complex in two-phase flows, become even more complex.

Two-phase, gas-liquid and liquid-liquid flows are described in Section 154 and Section 157. In this section two-phase, gas-liquid and liquid-liquid flows will only be described as necessary for the three-phase flow descriptions.

In contrast to two-phase, gas-liquid flow, where many different kinds of models and semi-empirical relations have been presented over the last 40 years, the prediction models for three-phase, gas-liquid flow are very limited in number. The early investigators predicted three phase flow by modification of the liquid properties combined with the two-phase, gas-liquid models. Based on the experimental findings reviewed by Valle (1998) this approach to describing three phase flow is not sufficient on a general basis. In this section models and modified closure relations for three phase flow will be discussed for stratified flow and the extension to more complex flow patterns will be discussed.

For horizontal and slightly inclined pipes, four distinct gas-liquid flow patterns can be defined namely: stratified, annular, slug and bubbly flow.