Page 155 - Petroleum and Gas Field Processing

Figure 2 Schematic representation of (A) a non-dispersed system, (B) an O/W
emulsion, and (C) a W/O emulsion.

the possibility of forming reverse emulsions (oil-in-water, or O/W emulsion)
increases. This is type B in Figure 2.
For two liquids to form a stable emulsion, three conditions must
exist:
1. The two liquids must be immiscible.
2. There must be sufficient energy of agitation to disperse one
phase into the other.
3. There must be the presence of an emulsifying agent.
Conditions 2 and 3 are discussed in the following subsections.

5.2.1 Energy of Agitation
Emulsions normally do not exist in the producing formation, but are formed
because of the agitation that occurs throughout the oil production system.
Starting within the producing formation, the oil and water migrate through
the porous rock formation, making their way into the wellbore, up the well
tubing, through the wellhead choke, and through the manifold into the
surface separators. Throughout this journey, the fluids are subjected to
agitation due to the turbulent flow. This energy of agitation, which forces the
water drops in the bulk of oil, functions in the following pattern:
First, energy is spent to overcome the viscous force between the liquid
layers, leading to their separation into thin sheets or parts. This is what we
call ‘‘shearing energy’’ and is mathematically approximated by the formula
SE ¼ AD o ð1Þ
where SE is the shearing energy, A is the shear surface area, D o is the
characteristic length, and is the shearing force per unit area, which is
defined by Eq. (2) as follows:

C d u 2
¼ ð2Þ
2g c

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