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namic viscosity η=σ/ .
γ
&
It is frequently assumed that above the pour point, the pa-
rameters of a crude oil (e.g., its viscosity) follow temperature de-
pendencies, described by Arrhenius-type equations with a constant
activation energy U [12,13]. Accordingly, we calculated the “appar-
ent” Arrhenius activation energies of a viscous flow U
app
for the en-
tire temperature range T
m
=8–32°C. As a next approximation, we
determined the effects of the measurement temperature on the
“current” activation energy U(T
m
), calculated for consecutive 2°C
intervals of T
m
.
The pour points T
pour
of oil samples we determined as tem-
peratures, at which the measured or extrapolated plastic viscosi-
ties reached the value of 10 Pa·s (as recommended by the XI’s
World Petroleum Congress, London 1983).
3. Results and discussion
3.1. Effects of thermal pre-treatment on
pour points of crude oil samples
One of the main results of the present studies is that even
comparatively small variations of the pre-treatment temperature
T
pt
may lead to the drastic changes of thermophysical parameters
of crude oils, measured at lower temperatures.
Fig. 1. Effects of the thermal
pre-treatment of the crude oil on its
pour point.
42
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