Rarely does oil production takes place without water accompanying the oil. Salt water is thus produced with oil in different forms as follows:
- Free Water (F.W.)
- Suspended Water (SS.W) 3- Soluble Water (S.W.)
4- Emulsified Water (E.W.) which may be Oil in water emulsion O/W, or water in oil emulsion W/O.
Apart from free water, emulsified water (water-in-oil emulsion) is the one form that poses all of the concerns in the dehydration of crude oil.
Oil emulsions are mixtures of oil and water. In general, an emulsion can be defined as a mixture of two immiscible liquids, one of which is dispersed as droplets in the other (the continuous phase), and is stabilized by an emulsifying agent. In the oil field, crude oil and water are encountered as the two immiscible phases together. They normally form water-in-oil emulsion (W/O emulsion), in which water is dispersed as fine droplets in the bulk of oil. This is represented in figure 4-1.
However, as the water cut increases, the possibility of forming reverse emulsions (oil-in-water, or O/W emulsion) increases. This is represented in Figure 4-2.
For two liquids to form a stable emulsion, three conditions must exist:
- The two liquids must be immiscible.
- There must be sufficient energy of agitation to disperse one phase into the other.
- There must be the presence of an emulsifying agent.