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Single-wire guidance system for drilling boreholes

  • US 5,515,931 A
  • Filed: 11/15/1994
  • Issued: 05/14/1996
  • Est. Priority Date: 11/15/1994
  • Status: Expired due to Term
First Claim
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1. A method for guiding the drilling of a borehole along a path below the Earth'"'"'s surface comprising:

  • positioning an elongated electrically conductive and insulated guidewire adjacent a desired path to be followed by a subsurface borehole to be drilled, the desired path extending through a resultant static magnetic field including at least the Earth'"'"'s apparent magnetic field;

    connecting a first terminal of a current source to a first end of said guidewire;

    connecting a second end of said guidewire to electrical ground at the Earth'"'"'s surface;

    connecting a second terminal of said current source to electrical ground at the Earth'"'"'s surface to provide a return ground path for current flowing in the guidewire;

    supplying from said source a current of known amplitude in a first direction to said first end of said guidewire to cause said current to flow to said electrical ground at said second end of said guidewire and to return through the Earth to said second terminal of said source for a first period of time to produce a changes in said resultant static magnetic field in the region of said desired path;

    measuring, at a subsurface borehole being drilled through the Earth along said Path, vector components of said resultant static magnetic field; and

    ;

    determining, from changes in said vector components of said resultant magnetic field, the distance and direction from said borehole being drilled to said guidewire.

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