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IEEE Transactions on Antennas and Propagation
Volume 48 Number 9, September 2000

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Petrophysics of Magnetic Dipole Fields in an Anisotropic Earth

Allen Q. Howard Jr Fellow, IEEE

Page 1376.

Abstract:

Measurement-while-drilling (MWD) resistivity log data are often acquired in highly deviated or horizontal holes. The loop sensors are located on the drill collar and are approximated as magnetic dipoles. The conductivity of the earth in the vertical direction v and horizontal direction h are almost always different. When an MWD resistivity tool enters a new bed, the response is compared with the precomputed logs to aid in the determination of the location of the drill bit. The MWD tool response, however, is sensitive to resistivity anisotropy. An alternative method is used to derive analytical expressions for the Sommerfeld-type integrals. Numerical results give typical MWD tool response as a function of the inclination angle the tool makes with respect to the axes of anisotropy and also as a function of the anisotropy index = (h/vv)1/2 .

References

  1. D. V. Ellis, Well Logging for Earth Scientists, New York: Elsevier, 1987, pp.  84-96. 
  2. J. H. Moran and S. Gianzero, "Effects of formation anisotropy on resistivity-logging measurements", Geophys., vol. 44, no. 7, pp.  1266-1286, 1979 .
  3. J. R. Wait, Geo-Electromagnetism, New York: Academic, 1982.
  4. T. Hagiwara, "EM log response to anisotropic resistivity in thinly laminated formations with emphasis on 2-MHz resistivity devices", SPE Formation Evaluation, Soc. Petroleum Eng., SPE paper 28 426, 1996.
  5. J. D. Klein, P. R. Martin and D. F. Allen, "The petrophysics of electrically anisotropic reservoirs", in Proc. Soc. Petrol. Well-Log Analysts (SPWLA) 36th Annu. Logging Symp. , Paris, France,June 1995.
  6. J. A. Stratton, Electromagnetic Theory, New York: McGraw-Hill, 1941, p.  23. 
  7. C. Schlumberger, M. Schlumberger and E. G. Leonardon, "Some observations concerning electrical measurements in anisotropic media and their interpretation", Trans. Amer. Inst. Mining Eng. (AIME), vol. 110, pp.  159-182, 1934.
  8. M. Abramowitz and I. A. Stegun, Handbook of Mathematical Functions, Washington, DC: U.S. Govt. Printing Office, 1965.