Water and crude oil emulsions can
be produced during oilfield operations.
Since most oilfields are in the secondary or tertiary recovery stages,
the amount of produced water is not negligible. Furthermore, enhanced
oil recovery makes use of surfactants injection (chemical substances
that lower the surface tension of the liquid) and polymer flooding
(polymers are large molecules, composed of repeating blocks bounded
together, which are injected to decrease the water–oil mobility
ratio), leading to increased emulsion problems. Knowledge of fluid
petrochemical properties and behavior is fundamental for designing
the production system, transport infrastructures, and refinery layout.
Depending on the fluid composition, the flow rate, and the PVT conditions,
different physical behaviors and flow patterns will occur. Even though
significant effort has been carried out to take a broader view of
liquid–liquid models, there is a wide range of correlations
to consider with different crude oil compositions and diverse field
conditions. In this work, a critical review was carried out to assess
the main principles that affect an emulsion, how the flow patterns
are influenced by the water fraction, which equations can be used
to estimate the main physical properties, and last what are the methods
or techniques for identifying or characterizing an emulsion. As a
result, a strong background in this matter is offered, and future
research directions are synthesized.