Emulsions, Microemulsions, and Lyotropic Liquid Crystals - Surface and Colloid Chemistry: Principles and Applications - page 211

necessary to cross a direct cubic LC phase along the emulsification path, and it is also
crucial to remain in this phase long enough to incorporate all of the oil into the liq-
uid crystal. When the nanoemulsion forms, the oil is already intimately mixed with
all of the components and only has to be redistributed. Results show that smaller
droplet sizes are obtained when the LC zone is wide and extends to have high water
content because, in this case, during the emulsification process, the system remains
long enough in the LC phase to allow the incorporation of all of the oil. Around the
optimal formulation variables, the LC zone crossed by the system during emulsifica-
tion is wide enough to incorporate all of the oil, whatever mixing or stirring rate is
used, and then the resulting droplet size is independent of the preparation variables.
However, when the composition is far from this optimum, the LC zone becomes
narrower, and the mixing of components controls nanoemulsion formation. High
agitation rates and/or low addition rates are required to ensure the dissolution of all
of the oil into this phase.
9.5.3.6.1.2 Microemulsion Technology for Oil Reservoirs A new microemul-
sion additive has been developed that is effective in remediating damaged wells and
that is highly effective in fluid recovery and relative permeability enhancement when
applied in drilling and stimulation treatments at dilute concentrations. The micro-
emulsion is a unique blend of biodegradable solvent, surfactant, cosolvent, and water.
The nanometer-sized structures are modeled with structures that, when dispersed in
the base treating fluid of water or oil, permit a greater ease of entry into a damaged
area of the reservoir or fracture system. The structures maximize surface energy
interaction by expanding to 12 times their individual surface areas to allow maximum
contact efficiency at low concentrations (0.1-0.5%). Higher loadings on the order of
2% can be applied in the removal of water blocks and polymer damage. Laboratory
data are available for the microemulsion in speeding the cleanup of injected fluids in
tight gas cores. Further tests show that the microemulsion additive results in lower
pressures to displace fracturing fluids from propped fractures, resulting in lower
damage and higher production rates. This reduced pressure is also evident in pump-
ing operations in which friction is lowered by 10-15% when the microemulsion is
added to fracturing fluids. Field examples are shown for the remediation and fracture
treatment of coals, shales, and sandstone reservoirs, where productivity is increased
by 20-50%, depending on the treatment parameters. Drilling examples exist in hori-
zontal drilling where wells clean up without the aid of workover rigs, whereas offsets
typically require weeks of workover.
Terpene‑based microemulsion cleaning composition has been reported in some
industrial applications. Oil-in-water microemulsion cleaning compositions comprising
four principal components were described based on four components. These were
1. Terpene solvent (e.g., D-limonene)
2. An aliphatic glycol monoether cosolvent (e.g., dipropylene glycol monom-
ethyl ether)
3. A mixture of nonionic surfactants , consisting of a capped alkylphenol
ethoxylate or an ethoxylated higher aliphatic alcohol
4. A fatty acid alkanolamide and water