Summary
Although several models to determine the formation temperature in the
modelling of thermal production and injection processes have already been
suggested, there is no rigorous or systematic comparison between these models'
predictions that can guide the choice of the most appropriate one. Another
issue in thermal wellbore simulators is the commonly used assumption of
semisteady-state heat transfer from the wellbore up to the cementing/formation
interface. The effect of the semisteady-state assumption vs. the unsteady-state
assumption for the heat transfer from the wellbore up to the formation has not
received much attention in the literature and can be important in some
cases.
The results of a detailed analysis of the two previously described issues
can be implemented in all thermal wellbore and reservoir simulators to increase
their accuracy.
The previously described stated issues will be addressed in the present work
by developing a numerical nonisothermal two-phase wellbore simulator coupled
with tubular and cement material and surrounding formation. The first issue
will be studied in detail by comparing five different models for the formation
temperature treatment (FTT) plugged in the developed thermal wellbore
simulator.
Investigation of the second issue will be achieved by analyzing the three
critical items: first, a 2D heat transfer PDE model of the formation is
discretized in a general form; second, the gridding system is shifted from the
formation toward the casing; and third, an effective specific heat capacity for
the casing is used. The effects of choosing different models for FTT and using
either the unsteady-state or the semisteady-state assumption in the heat loss
from the wellbore up to the formation will be investigated. The model will be
validated against field data to show its merits in predicting the casing
temperature.
The entire wellbore system contains wellbore, tubing, insulation, annulus,
casing, cementing and formation. A fundamental understanding of this system is
still a challenging issue in the petroleum industry, and its accurate modelling
and coupling with reservoirs has become increasingly significant as more energy
resources are sought.
© 2010. Society of Petroleum Engineers
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History
- Original manuscript received:
27 June 2010
- Meeting paper published:
1 November 2010
- Revised manuscript received:
8 November 2010
- Manuscript approved:
9 November 2010
- Published online:
1 January 2011
- Version of record:
1 January 2011
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