Нефтегазовые нанотехнологии для разработки и эксплуатации месторождений. Часть 2. Евдокимов И.Н - 12 стр.

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uid is classified as a “colloidal suspension”,
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while systems with
particles which are formed by reversible “micellization” are classi-
fied as “association colloids”
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which usually exhibit a very rich
phase behavior ranging from the simplest isotropic micellar phases
to highly organized supramolecular nanostructures.
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As an example, Fig. 3 shows a complex temperature concen-
tration (T–C) phase diagram for nonionic surfactant penta-
ethyleneglycol dodecyl ether (C
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E
5
) in water.
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Note the appear-
ance of enclosed phase domains (“closed loops”) at the phase dia-
gram, representative of a so-called reentrant phase behaviour.
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For further discussion it is important that “closed loops” are in-
dicative of polymorphism of a system;
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these loops originate in
liquid-liquid immiscibility phenomena and are characteristic sig-
natures of directional noncovalent (e.g. hydrogen) bonding in asso-
ciating species.
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It is amazing that after introducing a concept of “micelliza-
tion” for nanoparticles of asphaltenes, the petroleum researchers
remained content with the obsolete notion of a single critical con-
centration (CMC) in surfactants. Consequently, a possible analogy
with known complex properties of association colloids (rich phase
diagram, hence multiple critical concentrations/temperatures) has
not been investigated, though, as shown in the following sections,
well known published experimental results and recent publications
provide multiple data in support of the concept of asphaltenes be-
ing “association nanocolloids”.
T-C Phase Diagram of Asphaltenes in Petroleum –
Data Accumulation
Phase changes in asphaltene-containing systems can be identified
by revealing “specific points” (singled out by steplike changes, ex-
trema, inflections etc.) in experimental concentration and tempera-
ture dependencies of system’s parameters. Fig. 4 shows an example
from our publication on concentration and temperature effects on
Herschel–Bulkley’s rheological parameters in asphaltene-rich
model oils.
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