Abstract :
Three high resolution temperature logs recorded after shut-in of the main borehole KTB-
Oberpfalz HB of the German Continental Deep Drilling Program are used to determine a
®rst estimate of the undisturbed formation temperature, using the line source model of
Bullard [Bullard, E.C., 1947. The time necessary for a borehole to attain temperature
equilibrium. Monthly Notices Royal Astronomical Society, Geophysical Supplement 5,
127±130.]. The resulting formation temperature pro®le and the corresponding temperature
gradient, deviate from previous estimates [Wilhelm, H., Baumann, C., Zoth, G., 1995. Some
results of temperature measurements in the KTB main borehole, Germany. Geothermics 24,
101±113; Clauser, C., Giese, P., Huenges, E., Kohl, T., Lehmann, H., Rybach, L., Safanda,
J., Wilhelm, H., Windlo, K., Zoth, G., 1997. The thermal regime of the crystalline
continental crust: implications from the KTB. Journal Geophysical Research 102, 18,417±
18,441; Wilhelm, H., 1998. Comparison of predicted and logged temperatures in the KTB
main hole. In: Popov, Yu, Pimenov, V. (Eds.), Proc. Int. Conf. The Earthʹs Thermal Field
and Related Research Methods. Moscow State Geological Prospecting Academy, Moskow,
pp. 280±281], which were derived from bottomhole measurements and from multiple
temperature logs recorded during drilling pauses at 4500, 6000 and 7200 m depth. Although
the database is not large enough to allow a formal error estimate, the noise in the
extrapolated formation temperature indicates a mean error of about20.15 K between 2500
and 5200 m depth and a mean error of 20.5 K below 5200 m depth. 7 2000 CNR.
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