 |
| Titel |
Statistically significant data base of rock properties for geothermal use |
| VerfasserIn |
Andreas Koch, R. Jorand, C. Clauser |
| Konferenz |
EGU General Assembly 2009
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250023455
|
|
|
|
|
|
| Zusammenfassung |
| The high risk of failure due to the unknown properties of the target rocks at depth is a major
obstacle for the exploration of geothermal energy. In general, the ranges of thermal and
hydraulic properties given in compilations of rock properties are too large to be
useful to constrain properties at a specific site. To overcome this problem, we study
the thermal and hydraulic rock properties of the main rock types in Germany in a
statistical approach. An important aspect is the use of data from exploration wells
that are largely untapped for the purpose of geothermal exploration. In the current
project stage, we have been analyzing mostly Devonian and Carboniferous drill
cores from 20 deep boreholes in the region of the Lower Rhine Embayment and
the Ruhr area (western North Rhine Westphalia). In total, we selected 230 core
samples with a length of up to 30 cm from the core archive of the State Geological
Survey.
The use of core scanning technology allowed the rapid measurement of thermal
conductivity, sonic velocity, and gamma density under dry and water saturated conditions
with high resolution for a large number of samples. In addition, we measured porosity,
bulk density, and matrix density based on Archimedes’ principle and pycnometer
analysis.
As first results we present arithmetic means, medians and standard deviations
characterizing the petrophysical properties and their variability for specific lithostratigraphic
units. Bi- and multimodal frequency distributions correspond to the occurrence of different
lithologies such as shale, limestone, dolomite, sandstone, siltstone, marlstone, and
quartz-schist. In a next step, the data set will be combined with logging data and
complementary mineralogical analyses to derive the variation of thermal conductivity with
depth. As a final result, this may be used to infer thermal conductivity for boreholes
without appropriate core data which were drilled in similar geological settings. |
|
|
|
|
|
|