The area of conformance improvement technology (CIT)
encompasses
the application of a myriad range of conventional fluids, including
polymers, gels, foams, polymer-enhanced gels and foams, bacteria,
and emulsions. However, these routes show operational limitations
in terms of chemical degradation, thermal degradation, formation damage,
susceptibility to high salinity, and segregation within pore spaces.
To mitigate these problems, it is necessary to employ conformance
agents that can be effectively tuned for a wide variety of reservoir
conditions. Microemulsions
are a promising class of fluids that exhibit thermodynamic stability,
robust structure, and tunable properties. The concept of this research
is to inject the optimal (correct) dosage of surfactants, which form
micelles with in situ hydrocarbons to form microemulsions.
Microemulsions are characterized by direct and reverse micelles, which
contribute to their intermolecular interactions responsible for fluid
stability and propagation under dynamic shear conditions. Design and
reservoir considerations must comprise of a number of factors, namely,
salinity, pH, temperature, slug concentration, and fluid activation/placement.
An optimal microemulsion can be identified by understanding the flow
mechanisms while accounting for mobility control, rock permeability
and heterogeneity, thief zone permeabilities, and the presence of
anomalies. It has been established in this review that microemulsions
help plug the high permeability pore throats via a combination of
the “Jamin effect” and viscosity modification. By adoption
of a proper workflow design, the reservoir may be tuned via the introduction
of microemulsions to suit the needs of the industry. However, considerable
research is still needed to validate the design aspects and application
of microemulsions for conformance improvement.