Page 88 - Petroleum and Gas Field Processing

increases, field facilities for control or elimination of water are to be
added. This identifies the second function of a GOSP. If the effect of
corrosion due to high salt content in the crude is recognized, then modern
desalting equipment could be included as a third function in the GOSP
design.
One has to differentiate between ‘‘dry’’ crude and ‘‘wet’’ crude. The
former is produced with no water, whereas the latter comes along with
water. The water produced with the crude is a brine solution containing
salts (mainly sodium chloride) in varying concentrations.
The input of wet crude oil into a modern GOSP consists of the
following:
1. Crude oil.
2. Hydrocarbon gases.
3. Free water dispersed in oil as relatively large droplets, which will
separate and settle out rapidly when wet crude is retained in the
vessel.
4. Emulsified water, dispersed in oil as very small droplets that do
not settle out with time. Each of these droplets is surrounded by
a thin film and held in suspension.
5. Salts dissolved in both free water and in emulsified water.
The functions of a modern GOSP could be summarized as follows:
1. Separate the hydrocarbon gases from crude oil
2. Remove water from crude oil
3. Reduce the salt content to the acceptable level [basic sediments
and water]
It should be pointed out that some GOSPs do have gas compression
and refrigeration facilities to treat the gas before sending it to gas
processing plants. In general, a GOSP can function according to one of
the following process operation:

1. Three-phase, gas–oil–water separation (See Chap. 4)
2. Two-phase, gas–oil separation
3. Two-phase, oil–water separation
4. Deemulsification
5. Washing
6. Electrostatic coalescence
To conclude, the ultimate result in operating a modern three-phase
separation plant is to change ‘‘wet’’ crude input into the desired outputs,
as given in Figure 15. Outputs from a three-phase regular separation plant,
on the other hand, are as shown in Figure 16.

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