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| Titel |
Well-log based prediction of temperature models in the exploration of sedimentary settings: Examples from the North German Basin |
| VerfasserIn |
Sven Fuchs, Thomas Wonik, Andrea Förster |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250091848
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| Publikation (Nr.) |
 EGU/EGU2014-6161.pdf |
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| Zusammenfassung |
| Temperature-depth distributions are pivotal in subsurface studies in academia as
well as in georesources applications. In this regard, high-resolution temperature
profiles, logged under equilibrium thermal borehole conditions, are the ultimate
measure. However there are circumstances in which these measurements are not
available or only measured to a certain depth so that a temperature model needs
to developed. A prerequisite for such a model is the knowledge of the regional
heat flow and the geological conditions translated into lithology and thermal rock
properties.
For the determination of the rock thermal conductivity (TC) we propose a two-step
procedure: (1) the use of standard petrophysical well log and (2) the inversion of predicted
TC to temperature gradients by applying Fourier’s law of heat conduction. The prediction of
TC is solved by using set of equations (Fuchs & Förster, 2014) developed for matrix TC of
sedimentary rocks. The equations resulted from a statistical analysis of an artificial set of
mineral assemblages (consisting of 15 rock-forming minerals) typical for the different types
of sedimentary rocks. The matrix TC was transformed into bulk TC by using a well-log
derived porosity. TC vs. depth profiles corrected for in situ (p, T) conditions finally were used
in conjunction with a published site-specific heat-flow value to model a temperature profile.
The methodology is shown on the example of a 4-km deep borehole at Hannover in the North
German Basin. This borehole, drilled for geothermal use, penetrates thick Mesozoic
sediments and terminates in the Triassic Middle-Buntsandstein formation. The
temperature computation was performed, inter alia, for a borehole section in a depth range
between approx. 2,320 and 3,750 m. The applied approach is able to match both
predicted and measured equilibrium borehole temperature profiles with a resulting
uncertainty of less than 5 %. Interval temperature gradients vary on average by < 3
°C/km. |
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