Fracture and permeability of granite in superhot geothermal environments

Noriaki Watanabe, Kiyotoshi Sakaguchi, Hanae Saishu, Ryota Goto, Takuya Ishibashi, Atsushi Okamoto, Youqing Chen, Steven E. Ingebritsen, Takeshi Komai, Noriyoshi Tsuchiya

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Assuming that the brittle–ductile transition (BDT) drastically reduces rock permeability, potentially exploitable geothermal resources (permeability: >10-16 m2) consisting of supercritical water or superheated steam (>~400 °C) could occur only in rocks with unusually high transition temperatures such as basalt. However, fracturing is possible even in ductile rocks, and some permeability–depth relations proposed for the continental crust show no drastic permeability reduction due to the BDT. Here we introduce our published results of permeability measurements on high-temperature fractured granite, suggesting that the BDT is not the first-order control on rock permeability, and that potentially exploitable resources may occur in granitic rocks with much lower BDT temperatures (~360 °C) that comprise the bulk of the continental crust. We additionally introduce our published results of hydraulic fracturing experiments on granite from subcritical/brittle to supercritical/ductile conditions, confirming the possibility of well stimulation to create excellent fracture patterns that should allow the effective extraction of thermal energy in the superhot geothermal environments of >~400 °C.

Original languageEnglish
Title of host publication5th ISRM Young Scholars' Symposium on Rock Mechanics and International Symposium on Rock Engineering for Innovative Future, YSRM 2019
PublisherInternational Society for Rock Mechanics and Rock Engineering
Pages19-24
Number of pages6
ISBN (Electronic)9784907430047
Publication statusPublished - 2019
Event5th ISRM Young Scholars' Symposium on Rock Mechanics and International Symposium on Rock Engineering for Innovative Future, YSRM 2019 - Okinawa, Japan
Duration: 2019 Dec 12019 Dec 4

Publication series

Name5th ISRM Young Scholars' Symposium on Rock Mechanics and International Symposium on Rock Engineering for Innovative Future, YSRM 2019

Conference

Conference5th ISRM Young Scholars' Symposium on Rock Mechanics and International Symposium on Rock Engineering for Innovative Future, YSRM 2019
CountryJapan
CityOkinawa
Period19/12/119/12/4

Keywords

  • Fracture
  • Geothermal environment
  • Granite
  • Permeability
  • Supercritical temperature

ASJC Scopus subject areas

  • Geotechnical Engineering and Engineering Geology
  • Geology

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