Flow in pipe can consist of single phase flow (gas, oil, or water only) or more which can be called multiphase (gas and liquid). In general, fluid in pipe can flow from an inlet point to outlet point if the pressure at outlet point is smaller than the pressure at inlet point, Pout < Pin (ΔP>0). If the pressure at inlet point is equal to the pressure at outlet point, Pout = Pin (ΔP=0), then fluid flow along pipe will not happen.
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| Figure 1: Flow in Pipe Concept |
Figure 1 is a figure that show pipeline with inlet point consist of three pipe segments, segment 1 with pressure P1 and flow rate Q1 , segment 2 with pressure P2 and flow rate Q2, and segment 3 with pressure P3 and flow rate Q3. The fluid of three pipe segments will be streamed to a gathering pipe with outlet pressure as Pout and fluid flow rate as Qout. Flow rate Qout shall be the sum of Q1, Q2, and Q3, because the pipeline in Figure 1 is assumed there is not inhibitor there.
If Qout is not summation of three flow rate (Q1, Q2, and Q3), it indicate that there is leak in pipe flow. As was explained earlier that the fluid flows from high pressure to low pressure, so fluid from the third inlet segments will flow into outlet segment if the value of P1, P2, and P3 respectively is greater than Pout.
A case that could possibly occur on the fluid in pipe is the pressure in the inlet segment is smaller than Pout, so the fluid will experience back-flow. Backflow can occur in variety of possibilities, namely the fluid from inlet segment which has higher pressure will flow into inlet segment which has lower pressure. When this condition occurs, then the flow rate that reaches outlet point will not optimal. Similarly, for fluid flow in the production pipeline, if backflow occur, the fluid flow rate through separator will not optimal.