Page 130 - Petroleum and Gas Field Processing

Figure 2 Horizontal three-phase separator; bucket and weir design.

design of the second type (Fig. 2), normally known as the bucket and weir
design, eliminates the need for an interface controller.
The operation of the separator is, in general, similar to that of the
two-phase separator. The produced fluid stream, coming either directly
from the producing wells or from a free-water knockout vessel, enters the
separator and hits the inlet diverter, where the initial bulk separation of
the gas and liquid takes place due to the change in momentum and
difference in fluid densities. The gas flows horizontally through the gravity
settling section (the top part of the separator) where the entrained liquid
droplets, down to a certain minimum size (normally 100 mm), are separated
by gravity. The gas then flows through the mist extractor, where smaller
entrained liquid droplets are separated, and out of the separator through
the pressure control valve, which controls the operating pressure of the
separator and maintains it at a constant value. The bulk of liquid,
separated at the inlet diverter, flows downward, normally through a
downcomer that directs the flow below the oil–water interface. The flow of
the liquid through the water layer, called water washing, helps in the
coalescence and separation of the water droplets suspended in the
continuous oil phase. The liquid collection section should have sufficient
volume to allow enough time for the separation of the oil and emulsion

Copyright 2003 by Marcel Dekker, Inc. All Rights Reserved.