Prediction of the Formation of Water-in-Oil Emulsions - Mathematical Modelling and Numerical Simulation of Oil Pollution Problems - page 81

Table 3.10 Comparison of models
Point

Model I Model II Model III Total numbers of

data points

R 2 correlation
coefficient

0.46 0.69

Number of
parameters

14 15 5 screens

Number of
Gaussian sets

4 2

Errors on stable
emulsions

40% 5% 54% 42

Errors on
mesostable
emulsions

63% 26% 53% 43

Errors on
entrained type

10% 5% 9% 41

Errors on all
types

35% 12% 43% 126

Advantages Low coefficients Accurate, simpler

math

Very simple

Disadvantages Lower accuracy High coefficients Lower accuracy

(c) There are many different asphaltenes some of which make much more stable
emulsions than others. Recent work has shown that there are hundreds of asphal-
tene sub-components varying very much in composition and molecular size.
Thus the percent of asphaltenes (or resins) certainly does not tell the whole story
about the emulsion-stabilizers.

3.8 Conclusions

Water-in-oil emulsions are formed as a result of asphaltene and resin surfactant
characteristics in oil of moderate viscosity (50-2000mPa s). Four types of water-in-
oil products are formed: stable and meso-stable emulsions, entrained water in oil and
unstable (or those that do not form any of the other three types). Each of these types
has unique characteristics and are thought to be non-convertible to other types once
formed.
The knowledge that water-in-oil types exist and that a new scheme to classify
their stability enables the development of new and much more accurate emulsion
formation models. The density, viscosity, asphaltene and resin contents are used to
develop a regression equation to stability, which in turn predicts either an unstable or
entrained water-in-oil state or a meso-stable or stable emulsion. The new models can