EGU2020-20127, updated on 12 Jun 2020
https://doi.org/10.5194/egusphere-egu2020-20127
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Preliminary results from interdisciplinary fault characterization in the Bedretto Underground Laboratory

Alexis Shakas1, Hannes Krietsch1, Marian Hertrich1, Nima Gholizadeh1, Katrin Plenkers1, Hansruedi Maurer1, Matthias Meier1, Simon Loew1, Morteza Nejati1, Rebecca Hochreutener1, Xiaodong Ma1, Stefan Wiemer1, Thomas Driesner1, Domenico Giardini1, Francisco Serbeto2, Raymi Castilla2, and Peter Meier2
Alexis Shakas et al.
  • 1ETH Zurich, Department of Earth Sciences, Switzerland
  • 2Geo-Energie Suisse AG

Engineered Geothermal Systems (EGS) are gaining increasing popularity as a source of renewable energy without significant CO2 emissions. Fractured crystalline rock masses offer a promising environment for exploitation of geothermal energy. In such a setting, fractures and faults are the main conduits for fluid flow and heat transport. In-situ fracture permeabilities are usually too low at depths where rock mass temperatures are sufficiently high for geothermal energy production. Therefore, a suitable heat exchanger needs to be engineered by hydraulic stimulations. A proper in-situ characterization of the fracture geometry and hydro-mechanical properties is of primary importance for the design of the stimulation operations. This is often the most challenging task, since the majority of the fractures in the reservoir are usually inaccessible for direct characterization.

 

The Bedretto Underground Laboratory for Geosciences (BULG) provides a novel and unique environment to study EGS-related processes, such as seismo-hydro-mechanical fault zone response during hydraulic stimulation and subsequent fluid circulation experiments. The laboratory is hosted in an access tunnel from the Bedretto Valley in the Southern Swiss Alps to a railway tunnel from the Matterhorn-Gotthard-Bahn. The overburden of more than 1000 m above the BULG provides conditions that are approaching those of realistic EGS systems. For the rock mass characterization, three boreholes were drilled perpendicular to tunnel axis with lengths ranging from 190 m to 300 m.

 

We present first data sets from a variety of methodologies, ranging from hydrological tests to geophysical borehole- and remote-imaging. The complementary nature of these data sets allows us to construct a preliminary three dimensional geological model. Notably, the individual measurements yielded information over a multitude of scales, ranging from millimeter-scale core-log information to decameter scale low-frequency Ground Penetrating Radar measurements. Such a wide range of scales is critical for the characterization of EGS reservoirs. The most prominent feature found is a large-scale fracture zone that extends across the entire investigation volume. This fracture zone will be the target for upcoming stimulation experiments.

How to cite: Shakas, A., Krietsch, H., Hertrich, M., Gholizadeh, N., Plenkers, K., Maurer, H., Meier, M., Loew, S., Nejati, M., Hochreutener, R., Ma, X., Wiemer, S., Driesner, T., Giardini, D., Serbeto, F., Castilla, R., and Meier, P.: Preliminary results from interdisciplinary fault characterization in the Bedretto Underground Laboratory, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20127, https://doi.org/10.5194/egusphere-egu2020-20127, 2020

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