1887
Volume 44 Number 6
  • E-ISSN: 1365-2478

Abstract

Abstract

Sedimentary rocks beneath the Columbia River Basalt Group are recognized as having potential for oil and gas production, but the overlying layered basalts effectively mask seismic reflections from the underlying sediments. Four electromagnetic (EM) methods have been applied on profiles crossing Boylston Ridge, a typical east–west trending anticline of the Yakima Fold Belt, in an attempt to map the resistivity interface between the basalts and the sediments and to map variations in structure and resistivity within the sediments. The EM surveys detected strong variations in resistivity within the basalts, and in particular the continuous magnetotelluric array profiling (EMAP) revealed resistivity lows beneath the surface anticlines. These low resistivity zones probably coincide with fracturing in the core of the anticlines and they appear to correlate well with similar zones of low seismic velocity observed on a nearby seismic profile.

The controlled‐source EM surveys (in‐loop transient, long‐offset transient, and variable‐offset frequency‐domain) were designed in anticipation of relatively uniform high resistivity basalts, and were found to have been seriously distorted by the intrabasalt conductors discovered in the field. In particular, the resistivity sections derived from 1D inversions were found to be inconsistent and misleading. The EMAP survey provided the most information about the subsurface resistivity distribution, and was certainly the most cost‐effective. However, both controlled‐source and EMAP surveys call for accurate 2D or 3D inversion to accommodate the geological objectives of this project.

Loading

Article metrics loading...

/content/journals/10.1111/j.1365-2478.1996.tb00186.x
2006-04-28
2024-03-29
Loading full text...

Full text loading...

References

  1. BostickF.X.jr.1986. Electromagnetic array profiling (EMAP). 56th SEG meeting, Houston, USA, Expanded Abstracts, 60–61.
  2. FrischknechtF.C. and RaabP.V.1984. Time‐domain electromagnetic soundings at the Nevada test site, Nevada. Geophysics49, 981–992.
    [Google Scholar]
  3. HördtA., DruskinV.L., KnizhnermanL. and StrackK.M.1992. Interpretation of 3‐D effects in long‐offset transient electromagnetic (LOTEM) soundings in the Munsterland area, Germany. Geophysics57, 1127–1137.
    [Google Scholar]
  4. JarchowC.M., CatchingsR.D. and LutterW.J.1994. Large explosive‐source, wide‐recording aperture seismic profiling on the Columbia Plateau, Washington. Geophysics59, 259–271.
    [Google Scholar]
  5. LutterW.J., CatchingsR.D. and JarchowC.M.1994. An image of the Columbia Plateau. Geophysics59, 1278–1289.
    [Google Scholar]
  6. NewmanG.A.1992. Three‐dimensional electromagnetic inversion of insufficient and inaccurate data. 62nd SEG meeting, New Orleans, USA, Expanded Abstracts, 453–456.
  7. NewmanG.A., HohmannG.W. and AndersonW.L.1986. Transient electromagnetic response of a three‐dimensional body in a layered earth. Geophysics51, 1608–1627.
    [Google Scholar]
  8. ReidelS.P., FechtK.R., HagoodM.C. and TolanT.L.1989. The geologic evaluation of the central Columbia Plateau. In: Volcanism and Tectonism in the Columbia River Flood‐basalt Province (eds S.P.Reidel and P.R.Hooper ), Geological Society of America, Special Paper, 239, 247–263.
    [Google Scholar]
  9. SpiesB.R. and FrischknechtF.C.1991. Electromagnetic sounding. In: Electomagnetic Methods in Applied Geophysics‐Applications (ed. M.N.Nabighian ), Society of Exploration Geophysicists, 285–426.
    [Google Scholar]
  10. SpiesB.R. and ParkerP.D.1984. Limitations of large loop transient electromagnetic surveys in conductive terrains. Geophysics49, 902–912.
    [Google Scholar]
  11. StoyerC.H.1991. Integrated geosciences, inc. deep TEM field systems. In: Electromagnetic Methods in Applied Geophysics‐Applications (ed. M.N.Nabighian ), Society of Exploration Geophysicists, 412–413.
    [Google Scholar]
  12. TolanT.L. and ReidelS.P.1989. Structure map of a portion of the Columbia River flood‐basalt province. In: Volcanism and Tectonism in the Columbia River Flood‐basalt Province (eds S.P.Reidel and P.R.Hooper ), Geological Society of America, Special Paper 239.
    [Google Scholar]
  13. TolanT.L., ReidelS.P., BeesonM.H., AndersonJ.L., FechtK.R. and SwansonD.A.1989. Revisions to the estimates of the areal extent and volume of the Columbia River basalt Group. In: Volcanism and Tectonism in the Columbia River Flood‐basalt Province (eds S.P.Reidel and P.R.Hooper ), Geological Society of America, Special Paper, 239, 1–20.
    [Google Scholar]
  14. Torres‐VerdinC. and BostickF.X.jr.1992. Principles of spatial surface electric field filtering in magnetotellurics: Electromagnetic array profiling (EMAP). Geophysics57, 603–622.
    [Google Scholar]
  15. UnsworthM.A. and OldenbergD.1992. Two‐dimensional inversion of deep sea em data. A.G.U. Annual Fall Meeting, San Francisco (abstract).
  16. WarrenR.K. and SrnkaL.J.1992. Exploration in the basalt‐covered areas of the Columbia River Basin, Washington, using electromagnetic array profiling (EMAP). Geophysics57, 986–993.
    [Google Scholar]
  17. WiltM.J.1991. Interpretations of time‐domain electromagnetic soundings near geologic contacts. Ph.D. thesis, University of California, Berkeley .
  18. WiltM.J., MorrisonH.F., LeeK.H. and GoldsteinN.E.1989. Electromagnetic sounding in the Columbia Basin, Yakima, Washington. Geophysics54, 952–961.
    [Google Scholar]
http://instance.metastore.ingenta.com/content/journals/10.1111/j.1365-2478.1996.tb00186.x
Loading
  • Article Type: Research Article

Most Cited This Month Most Cited RSS feed

This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error