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Method and apparatus for azimuthal electromagnetic well logging using shielded antennas

  • US 6,191,586 B1
  • Filed: 06/10/1998
  • Issued: 02/20/2001
  • Est. Priority Date: 06/10/1998
  • Status: Expired due to Term
First Claim
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1. An improved well logging tool for making azimuthally sensitive resistivity measurements within a formation surrounding a drill string positioned within a borehole, said improved well logging tool comprising:

  • at least one transmitting antenna positioned on said drill string within said borehole, said transmitting antenna for generating a primary electromagnetic field within said surrounding formation, thereby inducing currents to flow within said formation which in turn generate a secondary electromagnetic field within said formation, said borehole, and said drill string;

    at least one receiving antenna positioned on said drill string, in spaced relationship with said transmitting antenna, said receiving antenna for measuring characteristics of said secondary electromagnetic field through induction of a current within said receiving antenna indicative of said characteristics;

    at least one conductive shield associated with said drill string in a manner as to partially shield said transmitting antenna or said receiving antenna or both;

    wherein said conductive shield defines a window through which said primary electromagnetic field may be generated or said secondary electromagnetic field may be detected by said transmitting or receiving antennas.

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