T- 1 TEMPERATURE DROP
position as a function of time under
different conditions. 12
Research into flow conditions for
crude oil produced at the Turija North
field has also occurred, 3 13 with the influence of paraffin content on the rheological properties of fluid analyzed.
Domestic Serbian crude oil, due to its
high paraffin content, and sometimes
asphaltene, behaves not only as a
Newtonian fluid, but also as a pseudo-plastic, or even as a Bigham fluid. 14-15
These fluids often have a high pour
point, sometimes above 30° C.
Heavy oil flow is possible in practice at lower temperatures than
pour point. 13 Aside from the cooling
achieved during fluid flow through
the pipeline, fluid composition also affects flow characteristics. Fluid can be a multiphase mixture
of oil and gas, or oil, gas, and reservoir water. 16-17 Dissolved
gas in oil can improve flow and reduce heavy oil’s viscosity.
This article will present a precise determination of the
minimum temperature that allows the flow of heavy oil, allowing heating systems to work at lower temperatures and
yielding energy savings. Such an approach would also reduce the amount of additives needed for lowering pour
point, further reducing costs.
0 100 200 300 400 500 600
Pour point, 29° C.
Viscosity changes can determine the critical, or lowest, tem-
perature at which the oil will flow (Fig. 1). There is a large
increase in viscosity at temperatures about 3-5° C. above
pour point. At these temperatures oil behaves like a non-
Newtonian fluid. Pour point can be considered a boundary
temperature for normal oil flow. At lower temperatures, oil
tends to thicken and take on a gel-like structure, further dis-
abling its flow. 13 18-19
vot= tm A,or not=vot:tot
A = 10 log (v) +m: logti
m = log t1 ti+ 1 log ni+ 1 ni
n og = a:n ot b
a = 10.715( 5.614 : RS + 100)-0.515
b = 5. 44( 5.614 : RS + 150)-0.338
RS = 0,1342 : t gr P 100,0009( 1,8t+ 32) 100,0125 to 141, 5 :131, 5 9 C ; E1,205 ( 7)
A, m – parameters for determining kinematic
viscosity of oil
a, b – parameters for determining dynamic viscosity
of oil with dissolved gas
vot – kinematic viscosity of oil, (sq m/sec) × 10-6
μog – dynamic viscosity of oil, Pa sec × 10-3
ρot – oil density, kg/cu m
μog – dynamic viscosity of oil with dissolved gas, Pa
sec × 10-3
RS – solution gas-oil ratio, cu m/cu m
ρS – relative density of gas
Pgr – pressure in pipeline, bar
t – temperature in pipeline, °C.
ti, i+ 1 – temperature values, °C.
μi, i+ 1 – oil viscosity values, Pa