Detection of a reservoir fracture by the use of sonic log data in EE-4, Higashi-Hachimantai

Hiroyuki Saito, Kazuo Hayashi

Research output: Contribution to journalConference articlepeer-review

1 Citation (Scopus)


This paper investigates the change of aperture of a fracture caused by borehole pumping with full-waveform acoustic logs (FWAL). The FWAL data was collected in the Higashi-Hachimantai Hot Dry Rock model field, Japan. In this field, a single fracture was induced hydraulically in intact welded tuff. The fracture aperture can be controlled by injection of water into the borehole. At the depth of the artificial fracture, P-wave and tube-vave amplitude deficits were observed. Time-frequency analysis was applied to obtain the rate of amplitude deficits in the frequency domain. Based on the depth range of the observed amplitude deficits, it is clear that there is a permeable zone about 1.4 m wide around the fracture. The amplitude deficits increased when wellhead pressure was increased from 0 MPa to 3 MPa. The maximum P-wave amplitude deficit rose from 76% to 85% and that of the direct tube-wave rose from 12% to 16%. A parallel plate fracture model was examined to estimate the fracture aperture using the amplitude deficit of the direct tube-wave. Estimated fracture aperture increased from 2.5 mm to 3.5 mm as wellhead pressure increased.

Original languageEnglish
Pages (from-to)433-437
Number of pages5
JournalTransactions - Geothermal Resources Council
Publication statusPublished - 1999 Dec 1
EventGlobal Geothermal Resources: Sustainable Energy for the Future - Reno, NV, USA
Duration: 1999 Oct 171999 Oct 20

ASJC Scopus subject areas

  • Renewable Energy, Sustainability and the Environment
  • Energy Engineering and Power Technology
  • Geophysics


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