Application of the tri-axial drill-bit VSP method to drilling for geological survey in civil engineering

  • Soma Nobukazu (National Institute of Advanced Industrial Science and Technology) ;
  • Utagawa Manabu (National Institute of Advanced Industrial Science and Technology) ;
  • Seto Masahiro (National Institute of Advanced Industrial Science and Technology) ;
  • Asanuma Hiroshi (Graduate School of Environmental Studies, Tohoku University)
  • Published : 2004.02.01

Abstract

We have examined the applicability of the triaxial drill-bit VSP method (TAD-VSP) to the geological survey of possible sites for a high-level radioactive waste disposal repository. The seismic energy generated by a drill bit is measured by a downhole multi-component detector, and the resulting signals are processed to image the geological structure deep underground. In order to apply the TAD-VSP method to civil-engineering-scale drilling, we have developed a small but highly sensitive and precise three-component downhole seismic measurement system, and recorded drill-bit signals at a granite quarry. We have successfully imaged discontinuities in the granite, possibly related to fractures, as highly reflective zones. The discontinuities imaged by the TAD-VSP method correlate well with the results of other borehole observations. In conclusion, the TAD-VSP method is usable in geological investigations for civil engineering because the equipment is compact and it is simple to acquire the drill-bit signal.

References

  1. Asanuma, H., Liu, H., Niitsuma, H., and Baria, R., 2000, Discrimination of polarization of reflected waves in the triaxial drill-bit VSP and imaging of subsurface structure at Soultz, France: Calgary, Canada: 70lhAnn. Internal. Mtg., Soc. Explor. Geophys., Expanded Abstracts
  2. Asanuma, H., and Niitsuma, H., 1995, Triaxial seismic measurement while drilling and estimation of subsurface structure: Geothermat Science amd Technoloey, 5,31-51
  3. Asanuma, H., Niitsuma, H., and Chubachi, N., 1990, An Analysis of Three Dimensional AE Lissajou Pattern during Well-dhlling and Estimation of Source Direction: in Yamaguchi, K., Takahashi, H. and Niitsuma, H., (Eds.), Progress in Acoustic Emission V: The Japanese Society for Non-Destructive Inspection, 436-43
  4. Cho, A., 2001, Report of in-situ rock stress measurement by the hydraulic fracturing method: Internal document of National Institute of Advanced Industrial Science and Technology
  5. Knapp, C.H., and Carter, G.C., 1976, The Generalized Correlation Method for Estimation of Time Delay: IEEE Trans. Acoustics Speech, Signal Processing, 24, 320-327
  6. Rector III, J.W., and Marion, B.P., 1991, The use of Drill-Bit Energy as a Downhole Seismic Source: Geophysics, 56, 628-634