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Extended range, pulsed induction logging tool and method of use

  • US 4,849,699 A
  • Filed: 06/08/1987
  • Issued: 07/18/1989
  • Est. Priority Date: 06/08/1987
  • Status: Expired due to Term
First Claim
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1. An apparatus for systematically logging an earth formation around a borehole using a logging sonde by generating a primary magnetic field in the formation at depth and detecting an induced secondary magnetic field indicative of a formation electrical parameter, comprising(i) means for generating a series of time spaced primary magnetic field pulses at a series of stations along the borehole;

  • (ii) means for detecting response data relative to a secondary magnetic field induced in said formation by each said primary magnetic field pulse, and (iii) means for processing said response data to provide an indication of at least one electrical parameter of the formation around the borehole;

    wherein said processing means includes (a) means for modeling the response of the adjacent formation using a series of assumed conductivity and bed thickness values along with actual parameters of the pulsed primary field, and (b) means for cross-checking a forward solution of (a) against detected components of the secondary magnetic field.

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