Page 159 - Petroleum and Gas Field Processing

Figure 6 Droplet size distribution for an emulsion sample.

5. Percentage of dispersed water: The presence of a small
percentage of water in oil under turbulence conditions could
lead to highly emulsified mixture. Water droplets are finely
divided and scattered with very little chance of agglomerating to
larger particles.
6. Salinity of emulsified water: Highly saline water will lead to a
faster separation because of a higher density difference between
the oil and the water phases.

5.3 DEHYDRATION/TREATING PROCESSES

The method of treating ‘‘wet’’ crude oil for the separation of water
associated with it varies according to the form(s) in which water is found
with the crude. Free-water removal comes first in the treating process,
followed by the separation of ‘‘combined’’ or emulsified water along with
any foreign matter such as sand and other sediments [1]. The basic
approaches of handling ‘‘wet’’ crude oils are illustrated in Figure 7.
Again, from an economic point of view, removal of free water at the
beginning will reduce the size of the treating system, hence its cost. The
same applies for the separation of associated natural gas from oil in the
gas–oil separator plant (GOSP).
A dehydration system in general comprises various types of
equipment. Most common are the following:
Free-water knockout vessel
Wash tank

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