Составители:
vated CH and CC bonds, the least reactive parts of organic com-
pounds.
5. Conclusions
We found that formation temperature has a very strong impact on
viscosity of crude oil and bitumen emulsions. At normal conditions
the materials possess a long-term memory of a thermal preload.
This memory is especially strong after formation at “critical” tem-
peratures of about 36–38°C. The “critical” sharp increase of viscos-
ity is attributed to structural phase transitions in asphaltene mo-
lecular aggregates. In W/O emulsions and in the matrix crude oil
these aggregates presumably stabilise the extended networks of
wax particles by emerging covalent bonding.
The weakening of the inner structures in bitumen emulsions
may be due to the presence of producer-added surfactants, other
than asphaltenes. In all studied emulsions, the “memory” of a
strong thermal preload (formation temperatures above the wax
melting point) may be explained by destruction of noncovalent hy-
drogen bonds and π-interactions.
We expect the observed thermally-induced aggregation to be a
common phenomenon in fluids, containing asphaltenes of any geo-
graphical or geological origin. This phenomenon could be the ex-
planation for some puzzling experiments where an enhanced ag-
gregation was registered in a regime where the destructive effect of
increased thermal motion was expected to dominate.
This study demonstrates the effectiveness of rheological
measurements as a means to indirectly elucidate the inner struc-
tures of petroleum and bitumen emulsions over a wide range of
temperatures. With this paper we hope to stimulate further re-
search work on thermodynamics and dynamics of asphaltene-
containing emulsions.
References
(1) Evdokimov I.N., Eliseev D.Yu., Eliseev N.Yu., 2001. J. Petrol. Sci. Eng.,
30 (3/4), p.199-211.
37
Страницы
- « первая
- ‹ предыдущая
- …
- 35
- 36
- 37
- 38
- 39
- …
- следующая ›
- последняя »
