Page 160 - Petroleum and Gas Field Processing

Figure 7 Basic approach of handling wet crude oil. (F.W. = fresh water, SS.W. =
suspended water, E.W. = emulsified water.)

Gun barrel
Flow treater (heater/treater)
Chemical/Injector
Electrostatic dehydrator

5.3.1 Removal of Free Water
Free water is simply defined as that water produced with crude oil and will
settle out of the oil phase if given little time. There are several good
reasons for separating the free water first:

1. Reduction of the size of flow pipes and treating equipment
2. Reduction of heat input when heating the emulsion (water takes
about twice as much heat as oil)
3. Minimization of corrosion because free water comes into direct
contact with the metal surface, whereas emulsified water does not.
Free water, on the other hand, has its distinctive benefits. Free water
found in the reservoir fluid will carry twice as much heat as oil and take it
up the tubing to the surface. Eventually, it will help in breaking oil
emulsions. It is to be observed that a well producing salt water (free water)
will be much warmer than a well producing oil only. Further, free water
contributes to what is called ‘‘water wash,’’ which is the action of the salt
water to break the oil emulsions (as will be discussed in Chapter 6).
Free water removal takes place using a knockout vessel, which could
be an individual piece of equipment or incorporated in a flow treater.

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