Нефтегазовые нанотехнологии для разработки и эксплуатации месторождений. Часть 2. Евдокимов И.Н - 22 стр.

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gradual decrease of RI due to thermal expansion, with the density

at the top being only marginally smaller than at the bottom. In-

deed this behavior was observed below ca. 28°C and, once again,

above ca. 37°C. At intermediate temperatures, in the vicinity of

asphaltene nanophase boundary, there was a strong transient

stratification of density and, presumably of composition of the oil.

Some of the effects induced at the nanophase boundary “A” may be

very long-lived, apparently governed not by thermodynamic but by

kinetic control.

E.g., pour point changes, illustrated in Fig. 9,

persisted for as long as four months.

Fig. 10. Kinetically controlled long-lived increase in the mass of deposits

from petroleum media, induced at asphaltene nanophase boundary “A”

(adapted from Ref. 14).

Another example of long-lived effects is from our recent study

of deposits at steel surfaces from petroleum fluids with high as-

phaltene content (12.3 g/l).

Filled symbols in Fig. 10 show depos-

its from a fluid which in its “thermal history” never has crossed the

phase boundary “A”. Open symbols show deposits from a fluid at

least once heated above 28–29°C. After that, the increase of deposi-

tion, characteristic to higher-temperature nanophase, persisted be-

low the phase boundary (at 12–29°C) for at least one month.