Prediction of the Formation of Water-in-Oil Emulsions - Mathematical Modelling and Numerical Simulation of Oil Pollution Problems - page 56

Chapter 3
Prediction of the Formation of Water-in-Oil
Emulsions

Merv Fingas

Abstract The formation of water-in-oil emulsions, amajor complication in oil spills,
is described. Research has shown that asphaltenes are the prime stabilizers of water-
in-oil emulsions and that resins are necessary to solvate the asphaltenes. It has also
been shown that many factors play a role, including the amount of saturates and the
oil viscosity. Two schemes are given to describe the formation of emulsions using
the characteristics of starting oils including the resin and asphaltene contents and the
viscosity. Essentially, water droplets injected into the oil by turbulence or wave action
can be stabilized temporarily by the oil viscosity and on a longer-term basis by resins
and then asphaltenes. Depending on the starting oil properties, four types of water-
in-oil types are created: meso-stable and stable emulsions, entrained water-in-oil
and unstable or those-that-do-not-form types. Each type is described and has unique
properties. For most oils, loss of lighter components by evaporation is necessary
before the oils will form a water-in-oil type. It was noted that variability in emulsion
formation is, in part, due to the variation in types of compounds in the asphaltene and
resins groups. Certain types of these compounds form more stable emulsions than
others within the same asphaltene/resin groupings. A review of numerical modelling
schemes for the formation of water-in-oil emulsions is given. A recent model is
based on empirical data and the corresponding physical knowledge of emulsion
formation. The density, viscosity, asphaltene and resin contents were correlated with
a new stability index. A simplified screening approach is also described. Although
of lesser accuracy, the approach is simple to implement.

3.1 Introduction

Water-in-oil emulsions sometimes form after oil products are spilled. These emul-
sions, often called chocolate mousse or “mousse” by oil spill workers, can make
the cleanup of oil spills difficult [ 7 ]. When water-in-oil emulsions form, the physical
properties of oil changes dramatically. As an example, stable emulsions contain from