EGU General Assembly 2020
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Slates: a potential rock type to extract geothermal energy from the underground?

Johannes Herrmann1, Erik Rybacki1, Wenxia Wang1, Harald Milsch1, Bianca Wagner2, and Bernd Leiss2
Johannes Herrmann et al.
  • 1GFZ German Research Centre for Geosciences, Geomechanics and Scientific Drilling, Potsdam, Germany (
  • 2Geoscience Centre of the Georg-August-University of Göttingen

Commonly used host rock reservoirs for Enhanced Geothermal Systems (EGS) are composed of granite, as they display highly conductive and sustainable fracture networks after stimulation. However, considering the large amount of metamorphic rocks in Europe’s underground, these rock types may also show a large potential to extract geothermal energy from the subsurface. Within the framework of the European Union’s Horizon 2020 initiative ‘MEET (Multi-Sites EGS Demonstration)’, we are conducting fracture permeability experiments at elevated confining pressures, pc, temperatures, T, and differential stresses,

How to cite: Herrmann, J., Rybacki, E., Wang, W., Milsch, H., Wagner, B., and Leiss, B.: Slates: a potential rock type to extract geothermal energy from the underground?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8091,, 2020.


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displays version 1 – uploaded on 21 Apr 2020
  • CC1: Comment on EGU2020-8091, Sheila Peacock, 29 Apr 2020

    Thank you for your presentation.  Shale and slate are very interesting because they are so anisotropic.  I could not tell from your Slide 5 whether the artificial fracture was paralllel or perpendicular to the bedding/cleavage planes of the sample.  Do you intend to repeat the experiment with samples cut perpendicular to the samples you used?

    Also, are you able to make any geophysical measurements on your samples that might be useful for the interpretation of well logs or permanent geophysical (time-lapse) monitoring systems, e.g. resistivity?


    • AC1: Reply to CC1, Johannes Herrmann, 29 Apr 2020

      Hi Sheila,
      thank you for your comment. You're right, it's not obvious from the sketch in slide 5, but all samples were drilled perpendicular to bedding orientation. Therefore, the orientation of the artificial fracture is sub-parallel to the bedding planes. However, as the matrix permeability of the investigated samples is so low, we think the influence of bedding orientation on the fracture permeability is negligible as we assume basically fluid only through the fracture. That it also induced by the used geometry.
      Unfortunately, we are not able to do resistivity logs on our samples. However, there might be a chance to do some velocity measurements which haven’t been planned yet, but may be interesting to think about. Thank You for the cue.

      Again, thanks for your questions! Best,