Laboratory and field verification of a new approach to stress measurements using a dilatometer tool

T. Ito, A. Sato, K. Hayashi

Research output: Contribution to journalArticlepeer-review

12 Citations (Scopus)

Abstract

A new method is proposed for in-situ stress measurements. The stresses are estimated from the borehole pressure required to open axial fractures emanating from the borehole, similar to hydrofracture stress measurements. However, the borehole is pressurized by inflation of a dilatometer, such as a packer and a sleeve, and the borehole pressure to reopen the fractures is detected from circumferential deformation of the borehole. The fractures are induced by hydraulic fracturing or sleeve fracturing in advance. To demonstrate this method, we developed a new dilatometer tool. The tool consists essentially of a packer around which deformation transducers sensitive to circumferential strain are affixed at 10°-30° intervals. The packer is inflated to touch the borehole wall, and then the packer pressure is increased step-wise and the resultant strains recorded. Initially, the circumferential strain developed around the borehole is radially symmetric. However, this becomes strongly asymmetric once the fractures begin to open. Thus, the records of strain at different locations around the borehole indicate both the reopening pressure and the orientation of fractures. In the case of a vertical borehole, the detected reopening pressure allows us to estimate the maximum horizontal stress on condition that the minimum horizontal stress is estimated using other approaches.

Original languageEnglish
Pages (from-to)1173-1184
Number of pages12
JournalInternational Journal of Rock Mechanics and Mining Sciences
Volume38
Issue number8
DOIs
Publication statusPublished - 2001 Dec

Keywords

  • Borehole deformation
  • Dilatometer
  • Hydraulic fracturing
  • Reopening pressure
  • Rock stress
  • Sleeve fracturing

ASJC Scopus subject areas

  • Geotechnical Engineering and Engineering Geology

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