A fluid can flow along pipes which have different shape; fluid flow direction can be divided into four categories, namely: vertical flow, horizontal flow, inclined flow, and directional flow. The direction of inclined and directional flow make angle of inclination between 0 to 90 degrees to horizontal axis. Figure 1 below shows the contribution of each category of flow direction on a production system.
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| Figure 1: Direction of Flow in a Production System |
Vertical and directional flow direction is typically used in pipelines beneath surface, the pipe connecting fluid from reservoir to surface (wellhead) of offshore platform. Once the fluid reaches surface, directions of flow is frequently involved are horizontal and inclined flow direction. The use of flow direction type is closely related in terms of determining the value of changes in pressure along pipe flow.
Multiphase flow in pipes can be defined as the concurrent movement of free gas and liquid in the pipe that can occur in various flow patterns. Gas and liquid can flow as homogeneous mixture, the liquid is at the front with the gas push behind liquid, liquid and gas may flow in parallel, or in various combinations of flow patterns that may occur.
Generally, the pattern of multiphase flow is divided into three types as follow:
- Segregated multiphase flow
In the segregated multiphase flow, the flow of gas phase is separated from liquid phase; it means that gas phase can flow above liquid phase or between the flow of liquid phase as shown in Figure 2.
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| Figure 2: Segregated Multiphase Flow |
- Intermittent multiphase flow
Flow pattern that can be included in the form of intermittent multiphase flow is the flow of liquid phase which hit the gas phase (Figure 3 bottom side) or the flow of liquid phase inhibit the flow of gas phase (Figure 3 top side).
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| Figure 3: Intermittent Multiphase Flow |
- Distributed multiphase flow
The pattern of distributed multiphase flow, gas and liquid phase are dispersed uniformly inside pipe flow, as shown in Figure 4.
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| Figure 4: Distributed Multiphase Flow |