Project title: HIGHER: High-temperature and high-pressure rheology of rock fractures: impacts on hydrothermal fluids circulation in magmatic systems.

Project description: Watanabe et al.’s (2017a) work published in Nature Geoscience critically challenges the scientific community’s hypothesis of a significant reduction in the formation permeability below the Brittle Ductile Transition (BDT) depth and argues in favour of prospectives of exploitable supercritical geothermal resources in the ductile crust. A subsequent Thermo-Hydro-Mechanical (THM) experimental study (Watanabe et al. 2017b) shows a drastic change in the fracture network morphology from planar to dendritic in supercritical conditions, which again supports the earlier argument. However, despite the significant implications of these findings, an adequate conceptual framework that describes these phenomena is yet to be formulated. The postulation of such a model can in turn be based on previous work by the German team but requires addressing several open questions relating fluid and rock rheology to fracture morphology and permeability evolution.

This study will unravel the complex mechanisms behind natural fracture formation beyond the brittle condition in the earth crust. To this purpose, further experiments will be conducted first at Tohoku University, decoupling each component thought to play a role in the dendritic fracture development, which are pore space, supercritical fluid rheology, and ductile rock rheology, in order to assess their individual impacts. Based on the experimental results, the constitutive model of rocks under brittle/ductile conditions being developed by the German partners will be further extended towards supercritical pore fluids and implemented into the open-source multi-physics code OpenGeoSys. Finally, large-scale simulations of earth crust processes such as hydro-thermal flows with evolving rock permeability, low-frequency earthquakes, or dyke propagation, etc. will be conducted by the German-Japanese team utilizing High Performance Computing (HPC) capabilities at the partner institutions.

Project duration: 02/2019 - 12/2022

Funding organisation: DFG - JSPS, the research work is also supported through a OCPC project


Project partners:

  • Technische Universität Bergakademie Freiberg
  • Tohoku University

Principal Investigator: Dr. Keita Yoshioka


  • Goto, Ryota, Kiyotoshi Sakaguchi, Francesco Parisio, Keita Yoshioka, Eko Pramudyo, and Noriaki Watanabe. "Wellbore stability in high-temperature granite under true triaxial stress." Geothermics 100 (2022): 102334.
  • Parisio, Francesco, Keita Yoshioka, Kiyotoshi Sakaguchi, Ryota Goto, Takahiro Miura, Eko Pramudyo, Takuya Ishibashi, and Noriaki Watanabe. "A laboratory study of hydraulic fracturing at the brittle-ductile transition." Scientific Reports 11, no. 1 (2021): 1-16.
  • Goto, Ryota, Noriaki Watanabe, Kiyotoshi Sakaguchi, Takahiro Miura, Youqing Chen, Takuya Ishibashi, Eko Pramudyo et al. "Creating cloud-fracture network by flow-induced microfracturing in superhot geothermal environments." Rock Mechanics and Rock Engineering 54, no. 6 (2021): 2959-2974.
  • Parisio, Francesco, Christoph Lehmann, and Thomas Nagel. "A model of failure and localization of basalt at temperature and pressure conditions spanning the brittle‐ductile transition." Journal of Geophysical Research: Solid Earth 125, no. 11 (2020): e2020JB020539.
  • Parisio, Francesco, and Keita Yoshioka. "Modeling fluid reinjection into an enhanced geothermal system." Geophysical Research Letters 47, no. 19 (2020): e2020GL089886.
  • Parisio, Francesco, Victor Vilarrasa, Wenqing Wang, Olaf Kolditz, and Thomas Nagel. "The risks of long-term re-injection in supercritical geothermal systems." Nature Communications 10, no. 1 (2019): 1-11.
  • Watanabe N., Numakura T., Sakaguchi K., Saishu H., Okamoto A., Ingebritsen S.E., and Tsuchiya N., (2017) Potentially exploitable supercritical geothermal resources in the ductile crust., Nature Geoscience, 10(2), 140-144.
  • Watanabe N., Egawa M., Sakaguchi K., Ishibashi T., and Tsuchiya N., (2017) Hydraulic fracturing and permeability enhancement in granite from subcritical/brittle to supercritical/ductile conditions. Geophysical Research Letter, 44, 5468-5475