1887
Volume 47, Issue 4
  • ISSN: 0812-3985
  • E-ISSN: 1834-7533

Abstract

[

We investigated the range of sensitivity of five tools for measuring the conductivity or resistivity in drillholes and on drill core. Each tool has a limited range of sensitivity, so one or more tools should be used to cover the range of values expected on a particular project.

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A study has been undertaken to acquire conductivity data using the EM39 low-induction-number conductivity tool. Measurements were taken in three holes in the Sudbury, Ontario, area: at Victoria in the south-west part of the Sudbury structure; at Levack, in the north range; and at the Lady Violet deposit near Copper Cliff. These data were compared with pre-existing data acquired using four other tools and measurements taken on core extracted from the holes. The four tools are the DGI galvanic downhole resistivity tool, the IFG downhole conductivity tool, and the handheld KT-10 and GDD meters. The comparison shows that each tool has a finite range of sensitivity. The resistivity tool used by DGI Geoscience is sensitive to conductivities primarily in the range 0.01 to 100 mS/m; the EM39 tool is sensitive to conductivities in the range of ~30 mS/m to 3000 mS/m and the IFG tool to conductivities greater than 30 mS/m. In the sub-ranges where the ranges of two instruments overlap, one might expect a good correlation between the measurements derived from the two tools. However, this is not always the case, as the instruments can have a different volume of sensitivity: the EM39 has a coil separation of 50 cm and will see material greater than 20 cm away from the hole; whereas the IFG conductivity tool seems to have a smaller spatial scale of sensitivity due to its 10 cm coil size. The handheld instruments used to log the conductivity of the core are sensitive to more conductive material (greater than ~1 S/m). The scale of the sensors of these handheld instruments is a few cm, so they are focussing on a very local estimate. The spatial characteristics of the handheld instruments are similar to the IFG tool, so there is a reasonable linear correlation between the conductivities derived from these three different instruments. However, the slopes are not unity; for example, the GDD instrument gives values three times greater than the KT-10. When selecting tools for measuring the resistivity and conductivity, ensure that the values that you expect to measure fall within the range of sensitivity of the instrument and that the features sought are comparable in size to the volume of sensitivity.

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2016-12-01
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References

  1. Bosch M. Zamora M. Utama W. 2002 Lithology discrimination from physical rock properties: Geophysics 67 573 581 10.1190/1.1468618
    https://doi.org/10.1190/1.1468618 [Google Scholar]
  2. Chopra, P., Papp, E., and Gibson, D., 2002, Geophysical well logging: geophysical and remote sensing methods for regolith exploration: CRCLEME Open File Report, 144, 105–115.
  3. Cochrane L. Thompson B. McDowell G. 1998 The application of geophysical methods to improve the quality of resource and reserve estimates: Exploration and Mining Geology 7 63 75
    [Google Scholar]
  4. Doetsch J. Coscia I. Greenhalgh S. Linde N. Green A. Gunther T. 2010 The borehole-fluid effect in electrical resistivity imaging: Geophysics 75 F107 F114 10.1190/1.3467824
    https://doi.org/10.1190/1.3467824 [Google Scholar]
  5. Elliott, B., Mwenifumbo, C., and McDowell, G., 1999, Borehole geophysical characteristics of the Lady Violet nickel deposit, Sudbury, Ontario: Proceedings of the Symposium on the Application of Geophysics to Engineering and Environmental Problems, 989–997.
  6. Jolliffe I. T. 1972 Discarding variables in a principal components analysis, 1: artificial data: Journal of the Royal Statistical Society. Series C, Applied Statistics 21 160 173
    [Google Scholar]
  7. Killeen, P., Mwenifumbo, C., Elliott, B., and Chung, C., 1997, Improving exploration efficiency by predicting geological drill core logs with geophysical logs, in A. G. Gubins, ed., Proceedings of Exploration 97: Fourth Decennial International Conference on Mineral Exploration, Mine Site Exploration and Ore Delineation, 713–716.
  8. McDowell, G. M., King, A., Lewis, R. E., Clayton, E. A., and Grau, J. A., 1998, In-situ nickel assay by prompt gamma neutron activation wireline logging: SEG, Annual Meeting, Expanded Abstracts, 1–4.
  9. McDowell, G. M., Fenlon, K., and King, A., 2004, Conductivity-based nickel grade estimation for grade control at Inco Sudbury mines: SEG, Annual Meeting, Expanded Abstracts, 1–4.
  10. McNeill, J., Bosnar, M., and Snelgrove, F., 1990, Resolution of an electromagnetic borehole conductivity logger for geotechnical and ground water applications: Geonics Technical Note TN-25, 1–28.
  11. Palacky, G. J., 1987, Resistivity characteristics of geologic targets, in M. N. Nabighian, ed., Electromagnetic methods in applied geophysics – theory, volume 1: SEG, Investigations in Geophysics, 3, 53–129.
  12. Parry, D. G., 2013, A comparative study of physical property measurements collected around the Sudbury Basin: M.Sc. thesis, Laurentian University.
  13. Reynolds, J., 1997, An introduction to applied and environmental geophysics: John Wiley and Sons Ltd.
  14. Smith R Shore M Rainsford D 2012 How to make better use of physical properties in mineral exploration: the exploration site measurement: The Leading Edge 31 330 337 10.1190/1.3694901
    https://doi.org/10.1190/1.3694901 [Google Scholar]
  15. White D. J. Milkereit B. Wu J. Salisbury M. H. Mwenifumbo J. Berrer E. K. Moon W. Lodha G. 1994 Seismic reflectivity of the Sudbury Structure North Range from borehole logs: Geophysical Research Letters 21 935 938 10.1029/93GL02609
    https://doi.org/10.1029/93GL02609 [Google Scholar]
  16. Williams, N. C., 2008, Geologically-constrained UBC-GIF gravity and magnetic inversions with examples from the Agnew-Wiluna greenstone belt, Western Australia: Ph.D. thesis, University of British Columbia.
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