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Potentially exploitable supercritical geothermal resources in the ductile crust

Nature Geoscience volume 10, pages 140144 (2017) | Download Citation

Abstract

The hypothesis that the brittle–ductile transition (BDT) drastically reduces permeability implies that potentially exploitable geothermal resources (permeability >10−16 m2) consisting of supercritical water could occur only in rocks with unusually high transition temperatures such as basalt. However, tensile fracturing is possible even in ductile rocks, and some permeability–depth relations proposed for the continental crust show no drastic permeability reduction at the BDT. Here we present experimental results suggesting that the BDT is not the first-order control on rock permeability, and that potentially exploitable resources may occur in rocks with much lower BDT temperatures, such as the granitic rocks that comprise the bulk of the continental crust. We find that permeability behaviour for fractured granite samples at 350–500 °C under effective confining stress is characterized by a transition from a weakly stress-dependent and reversible behaviour to a strongly stress-dependent and irreversible behaviour at a specific, temperature-dependent effective confining stress level. This transition is induced by onset of plastic normal deformation of the fracture surface (elastic–plastic transition) and, importantly, causes no ‘jump’ in the permeability. Empirical equations for this permeability behaviour suggest that potentially exploitable resources exceeding 450 °C may form at depths of 2–6 km even in the nominally ductile crust.

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References

  1. 1.

    The transition from hydrostatic to greater than hydrostatic fluid pressure in presently active continental hydrothermal systems in crystalline rock. Geophys. Res. Lett. 18, 955–958 (1991).

  2. 2.

    et al. Rhyolite magma drilled in Iceland could power the world’s hottest enhanced geothermal system. Geotherm. Res. Trans. 34, 765–770 (2010).

  3. 3.

    , & Drilling into magma and the implications of the Iceland Deep Drilling Project (IDDP) for high-temperature geothermal systems worldwide. Geothermics 49, 111–118 (2014).

  4. 4.

    , & The concept of the Iceland deep drilling project. Geothermics 49, 2–8 (2014).

  5. 5.

    , & Design and development of the discharge system of IDDP-1. Geothermics 49, 58–65 (2014).

  6. 6.

    , & Geologic controls on supercritical geothermal resources above magmatic intrusions. Nat. Commun. 6, 7837 (2015).

  7. 7.

    Transition from brittle fracture to ductile flow in Solenhofen limestone as a function of temperature, confining pressure, and interstitial fluid pressure Rock Deformation. Geol. Soc. Am. Mem. 79, 193–226 (1960).

  8. 8.

    Brittle-ductile transition in rocks. J. Geophys. Res. 73, 4741–4750 (1968).

  9. 9.

    et al. Magma-driven hydraulic fracturing and infiltration of fluids into the damaged host rock, an example from Dronning Maud Land, Antarctica. J. Struct. Geol. 27, 839–854 (2005).

  10. 10.

    & Permeability of the continental crust: implications of geothermal data and metamorphic system. Rev. Geophys. 37, 127–150 (1999).

  11. 11.

    et al. Hypocenter migration and crustal seismic velocity distribution observed for the inland earthquake swarms induced by the 2011 Tohoku-Oki earthquake in NE Japan: implications for crustal fluid distribution and crustal permeability. Geofluids 15, 293–309 (2015).

  12. 12.

    Hydrothermal processes related to movement of fluid from plastic into brittle rock in the magmatic-epithermal environment. Econ. Geol. 94, 1193–1211 (1999).

  13. 13.

    & Multiphase groundwater flow near cooling plutons. J. Geophys. Res. 102, 12235–12252 (1997).

  14. 14.

    , & Supercritical geothermal reservoir revealed by a granite-porphyry system. Geothermics 63, 182–194 (2016).

  15. 15.

    , & Reduction of permeability in granite at elevated temperatures. Science 265, 1558–1561 (1994).

  16. 16.

    , & Determination of aperture structure and fluid flow in a rock fracture by a high-resolution numerical modeling on the basis of a flow-through experiment under confining pressure. Wat. Resour. Res. 44, W06412 (2008).

  17. 17.

    et al. New ν-type relative permeability curves for two-phase flows through subsurface fractures. Wat. Resour. Res. 51, 2807–2824 (2015).

  18. 18.

    , , & Influence of macro-fractures and micro-fractures on permeability and elastic wave velocities in basalt at elevated pressure. Tectonophysics 503, 52–59 (2011).

  19. 19.

    et al. An experimental study of the brittle–ductile transition of basalt at oceanic crust pressure and temperature conditions. J. Geophys. Res. 117, B03213 (2012).

  20. 20.

    , , & Brittle versus ductile deformation as the main control of the deep fluid circulation in oceanic crust. Geophys. Res. Lett. 42, 2767–2773 (2015).

  21. 21.

    et al. Genesis of the plutonic-hydrothermal system around quaternary granite in the Kakkonda geothermal system, Japan. Geothermics 27, 663–690 (1998).

  22. 22.

    et al. High temperature measurements in well WD-1a and the thermal structure of the Kakkonda geothermal system, Japan. Geothermics 27, 591–607 (1998).

  23. 23.

    , & The significance of silica precipitation on the formation of the permeable-impermeable boundary within Earth’s crust. Terra Nova 26, 253–259 (2014).

  24. 24.

    & Heat flow regime in the Geysers-Clear Lake area of Northern California, USA. Geotherm. Res. Trans. 13, 491–502 (1989).

  25. 25.

    et al. The Campi Flegrei (Italy) geothermal system: a fluid inclusion study of the Mofete and San Vito fields. J. Volcanol. Geotherm. Res. 36, 303–326 (1989).

  26. 26.

    et al. in European Geothermal Update: Third International Seminar of E. C. Research and Demonstration Projects in the Field of Geothermal Energy 341–353 (D. Reidel Publishing Company, 1983).

  27. 27.

    , , , & Evidence for Li-rich brines and early magmatic fluid-rock interaction in the Larderello geothermal system. Geochim. Cosmochim. Acta 58, 1083–1099 (1994).

  28. 28.

    & Possible seismic signature of the α-β quartz transition in the lithosphere of Southern Tuscany (Italy). J. Volcanol. Geotherm. Res. 148, 81–97 (2005).

  29. 29.

    , , & Evidence of a supercritical fluid at depth in the Nesjavellir field. Proc. Fifteenth Workshop Geotherm. Reservoir Eng. SGP-TR-130, 81–88 (Stanford University, Stanford, 1990).

  30. 30.

    et al. Hybrid shallow on-axis and deep off-axis hydrothermal circulation at fast- spreading ridges. Nature 508, 508–512 (2014).

  31. 31.

    , & Porphyry-copper ore shells form at stable pressure–temperature fronts within dynamic fluid plumes. Science 338, 1613–1616 (2012).

  32. 32.

    The dynamic interplay between saline fluid flow and rock permeability in magmatic-hydrothermal systems. Geofluids 15, 350–371 (2015).

  33. 33.

    , & Influence of thermal damage on physical properties of a granite rock: porosity, permeability and ultrasonic wave evolutions. Constr. Build. Mater. 22, 1456–1461 (2008).

  34. 34.

    , , , & An experimental investigation on thermal damage and failure mechanical behavior of granite after exposure to different high temperature treatments. Geothermics 65, 180–197 (2017).

  35. 35.

    , , , & Permeability reduction of a natural fracture under net dissolution by hydrothermal fluid. Geophys. Res. Lett. 30, 2020 (2003).

  36. 36.

    et al. Evolution of fracture permeability through fluid–rock reaction under hydrothermal conditions. Earth Planet. Sci. Lett. 244, 186–200 (2006).

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Acknowledgements

The present study was supported in part by the Japan Society for the Promotion of Science (JSPS) through a grant-in-aid for Specially Promoted Research (no. 25000009). The authors would like to thank Toei Scientific Industrial Co., Ltd. for manufacturing the experimental system.

Author information

Affiliations

  1. Department of Environmental Studies for Advanced Society, Graduate School of Environmental Studies, Tohoku University, Sendai, Miyagi 9800845, Japan

    • Noriaki Watanabe
    • , Tatsuya Numakura
    • , Kiyotoshi Sakaguchi
    • , Atsushi Okamoto
    •  & Noriyoshi Tsuchiya
  2. Renewable Energy Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Koriyama, Fukushima 9630298, Japan

    • Hanae Saishu
  3. US Geological Survey, Menlo Park, California 94025, USA

    • Steven E. Ingebritsen

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Contributions

N.W. conducted overall study design and N.T. supervised the study. N.W., T.N. and K.S. conducted the experiments, analysed the results, and estimated the permeability–depth relation. H.S., A.O. and N.T. summarized temperature and depth conditions at the base of high-temperature geothermal reservoirs. N.W., H.S. and S.E.I. wrote the manuscript, and all authors commented on the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Noriaki Watanabe.

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DOI

https://doi.org/10.1038/ngeo2879

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