Environmental Engineering Reference
In-Depth Information
Fig. 8.6
Lost-circulation
zone detection with a
temperature log
Temperature Profiles in Production and Injection Wells
General
If left undisturbed, the temperature in a well bore will assume the ambient tempera-
ture of the surrounding formations; and a log of temperature against depth will indi-
cate the geothermal gradient. However, if the well is flowing, either due to production
or injection of fluids, then the observed temperature profile will depart from the geo-
thermal gradient. This surprisingly simple rule should always be borne in mind when
analyzing temperature logs. Look for departures from the geothermal gradient as the
prime indicator of fluid movement. Once a particular flow regime has reached ther-
mal equilibrium, the difference between the observed temperature in the borehole
and the geothermal gradient is related to the mass flow by the equation:
= /
where: ∆
T
= the temperature difference,
b
= a constant that depends on the physical
characteristics of the fluid produced and on the thermal conductivity of the forma-
tion,
M
= the mass flow rate, and
G
= the geothermal gradient.
Thus, other things being equal, the ∆
T
is proportional to the weight of fluid pro-
duced or injected per unit time.
D
T MG
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