T- 1 FLOW CONDITIONS
Pour point, 29° C.
; T = 2. 1° C.
10 15 20 25 30 35 40 45
Oil with dissolved gas
Oil without gas
conditions, 26. 9° C.
the oil with the balance remaining free. The amount of dissolved gas depends on pressure and temperature. Dissolved
gas in oil reduces viscosity and improves flow conditions.
Higher pressure increases the dissolved gas amount, allowing flow below the oil’s pour point. Fig. 2 presents the viscosity curve for heavy oil without dissolved gas.
Either laboratory measurements or Equation 1 can determine viscosity change. Parameters A and m are calculated in
Equations 2 and 3. Determining the minimum (boundary)
temperature conditions of heavy oil flow (with dissolved
gas) through a pipeline requires calculating its viscosity by
Chew and Connally, Equation 4, with parameters expressed
by Equations 5 and 6. Equation 7 determines the amount of
Oil viscosity’s dependence on the amount of dissolved gas
can be determined on the basis of known in-pipeline pressure and temperature using previous equations. A sudden increase in viscosity indicates flow boundary conditions. Fig.
2 presents the viscosity curve for oil with dissolved gas and
the new boundary conditions of flow. Temperature change
(∆T) defines the flow boundary condition change under the
influence of dissolved gas, quantifying the phenomenon as
observed in practice.
The pipeline heating system can be designed for a lower
working temperature, ∆T, than the existing one, resulting in
reduced electricity consumption and more efficient heavy oil
production. Presented methodology shows that the design of
a pipeline for heavy oil transportation not only must be done
on the basis of pour point, but also by determining the lowest possible flow temperature, laboratory measurements of
pour point not taking into account dissolved gas’s influence.
NEW T- 1 TEMPERATURE DROP
New boundary temperature 26° C.
The Turija North oil field provides an example for analysis of temperature flow conditions of heavy oil when the
fluid heating system is redefined and energy consumption
reduced. This field produces heavy oil from 60 wells and
has four gathering stations. Each well
is connected to a gathering station by
its own pipeline. The wells produce
between 2 and 23. 8 cu m/day at a gas-oil ratio (GOR) of 30-50 cu m/cu m
and produced water ranging from 5 to
70%. Average pour point is around 33°
C., but reaches as high as 40° C. for
some wells. Average paraffin content is
about 17%, with values in the range of
5-25%. The oil has unfavorable rheological characteristics.
Two typical well pipelines at the
Turija North oil field, T- 1 and T- 2, provide the basis for evaluation. Table 1
gives basic parameters of these well’s
pipelines. The pipelines are insulated
by polyurethane foam with thermal
conductivity of λ=0.03 W/m °C. and
50-mm thickness. A 9-kw electro induction heater installed at the beginning of the pipeline provides heat,
with the minimum soil temperature