Size effect in flow conductance of a closed small-scale hydraulic fracture in granite

Koji Matsuki, Jong Jin Lee, Kiyotoshi Sakaguchi, Kazuo Hayashi

Research output: Contribution to journalArticlepeer-review

32 Citations (Scopus)


Two-dimensional aperture distributions of a small-scale hydraulic fracture in granite were determined by measuring the height distributions of the two fracture surfaces along matched paths. Based upon the aperture data, water flow during closure of the fracture was simulated by solving the Reynolds equation for different flow areas at different positions. The main results obtained in this study are: (1) As the fracture closes, channeling flow becomes predominant and the flow conductance rapidly deviates from the value estimated by Darcy's law. A size-independent relation between a standardized mean aperture (e(m)/σ(o)) and the ratio of a hydraulic aperture to the mean mechanical aperture (e(h)/e(m)) was obtained for the small-scale hydraulic fracture. (2) The flow conductance at a given mean aperture decreases with the size of the flow area. This results fundamentally from the increase of the percentage of the contact point, which is caused by the increase of the initial standard deviation of the aperture with the size of the flow area.

Original languageEnglish
Pages (from-to)113-138
Number of pages26
JournalGeothermal Science and Technology
Issue number1-4
Publication statusPublished - 1999 Jan 1


  • Flow conductance
  • Hydraulic fracture
  • Reynolds equation
  • Size effect
  • Two-dimensional aperture distributions

ASJC Scopus subject areas

  • Water Science and Technology
  • Ocean Engineering
  • Management of Technology and Innovation


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