Hydraulic fracturing and permeability enhancement in granite from subcritical/brittle to supercritical/ductile conditions

Noriaki Watanabe, Motoki Egawa, Kiyotoshi Sakaguchi, Takuya Ishibashi, Noriyoshi Tsuchiya

Research output: Contribution to journalArticle

18 Citations (Scopus)

Abstract

Hydraulic fracturing experiments were conducted at 200–450°C by injecting water into cylindrical granite samples containing a borehole at an initial effective confining pressure of 40 MPa. Intensive fracturing was observed at all temperatures, but the fracturing characteristics varied with temperature, perhaps due to differences in the water viscosity. At the lowest considered temperature (200°C), fewer fractures propagated linearly from the borehole, and the breakdown pressure was twice the confining pressure. However, these characteristics disappeared with increasing temperature; the fracture pattern shifted toward the formation of a greater number of shorter fractures over the entire body of the sample, and the breakdown pressure decreased greatly. Hydraulic fracturing significantly increased the permeability at all temperatures, and this permeability enhancement was likely to form a productive geothermal reservoir even at the highest considered temperature, which exceeded both the brittle-ductile transition temperature of granite and the critical temperature of water.

Original languageEnglish
Pages (from-to)5468-5475
Number of pages8
JournalGeophysical Research Letters
Volume44
Issue number11
DOIs
Publication statusPublished - 2017 Jun 16

Keywords

  • brittle-ductile transition
  • granite
  • hydraulic fracturing
  • permeability
  • supercritical geothermal resource
  • supercritical water

ASJC Scopus subject areas

  • Geophysics
  • Earth and Planetary Sciences(all)

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