English
 
Privacy Policy Disclaimer
  Advanced SearchBrowse

Item

ITEM ACTIONSEXPORT
Add to Basket
  Local TagsRelease HistoryDetailsSummary

Released
Journal Article

Characterization of heterogeneities in the sandy facies of the Opalinus Clay (Mont Terri underground rock laboratory, Switzerland)

Authors
/persons/resource/slueth

Lueth,  S.
2.2 Geophysical Imaging of the Subsurface, 2.0 Geophysics, Departments, GFZ Publication Database, Deutsches GeoForschungsZentrum;

Steegborn,  Florian
External Organizations;

Heberling,  Frank
External Organizations;

Beilecke,  Thies
External Organizations;

Bosbach,  Dirk
External Organizations;

Deissmanm,  Guido
External Organizations;

Geckeis,  Horst
External Organizations;

Joseph,  Claudia
External Organizations;

Liebscher,  A.
External Organizations;

Metz,  Volker
External Organizations;

Rebscher,  Dorothee
External Organizations;

Rink,  Karsten
External Organizations;

/persons/resource/trond

Ryberg,  T.
2.2 Geophysical Imaging of the Subsurface, 2.0 Geophysics, Departments, GFZ Publication Database, Deutsches GeoForschungsZentrum;

Schennen,  Stephan
External Organizations;

External Ressource
No external resources are shared
Fulltext (public)

5024626.pdf
(Publisher version), 4MB

Supplementary Material (public)
There is no public supplementary material available
Citation

Lueth, S., Steegborn, F., Heberling, F., Beilecke, T., Bosbach, D., Deissmanm, G., Geckeis, H., Joseph, C., Liebscher, A., Metz, V., Rebscher, D., Rink, K., Ryberg, T., Schennen, S. (2024): Characterization of heterogeneities in the sandy facies of the Opalinus Clay (Mont Terri underground rock laboratory, Switzerland). - Geophysical Journal International, 236, 3, 1342-1359.
https://doi.org/10.1093/gji/ggad494


Cite as: https://gfzpublic.gfz-potsdam.de/pubman/item/item_5024626
Abstract
This contribution is presenting a multidisciplinary investigation of heterogeneities in a clay rock formation, based on seismic tomography, logging and core analysis, as a reconnaissance study for a diffusion experiment. Diffusion experiments in clay rock formations provide crucial experimental data on diffusive transport of radionuclides (RN) in extremely low hydraulic conductivity media. Previous diffusion experiments, conducted, for example, in the Mont Terri underground rock laboratory within the relatively homogeneous shaly facies of Opalinus Clay, and modelling studies of these experiments have demonstrated that the clay rock could sufficiently well be described as a homogeneous anisotropic medium. For other lithofacies, characterized by larger heterogeneity, such simplification may be unsuitable, and the description of heterogeneity over a range of scales will be important. The sandy facies of the Opalinus Clay exhibits a significantly more pronounced heterogeneity compared to the shaly facies, and a combined characterization and RN diffusion study has been initiated to investigate various approaches of heterogeneity characterization and subsequent diffusion in a heterogeneous environment. As an initial step, two inclined exploratory boreholes have been drilled to access the margins of the experiment location. These boreholes have been used to acquire a cross-hole tomographic seismic data set. Optical, natural gamma and backscattering logging were applied and rock cores were analysed. The integrated results of these investigations allowed the identification of an anomalous brighter layer within the investigated area of the sandy facies of approximately 1 m thickness and with its upper bound at roughly 10 m depth within the inclined exploratory wells. Mineralogical analyses revealed only slight variations throughout the rock cores and indicated that the anomalous layer exhibited a slightly higher quartz content, and locally significantly higher calcite contents, accompanied by a lower content of clay minerals. The anomalous layer was characterized by reduced natural gamma emissions, due to the lower clay content, and increased neutron backscattering likely indicating an increased porosity. Seismic P-wave velocities, derived from anisotropic tomography, exhibited a maximal gradient near the top of this layer. The transition from the overlaying darker rock matrix into this layer has been identified as an appropriate location for the setup of a tracer diffusion experiment in a heterogeneous environment.