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Method for near field electromagnetic proximity determination for guidance of a borehole drill

  • US 5,923,170 A
  • Filed: 03/26/1998
  • Issued: 07/13/1999
  • Est. Priority Date: 04/04/1997
  • Status: Expired due to Term
First Claim
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1. A method for electromagnetic proximity determination, comprising:

  • supplying a time-varying current having a repetitive waveform with periods of positive and negative current to a ferromagnetic solenoid source deployed in a borehole, said current at said solenoid source generating a non-sinusoidal, time-varying magnetic field with a known solenoid source strength parameter;

    detecting three vector components of the time-varying magnetic field at a sensor in a second, nearby borehole;

    obtaining from each of said three vector components an ensemble of individual magnetic field measurement values;

    determining times of polarity reversal of the field components;

    processing the ensemble of magnetic field measurement values for each of said three vector components with respect to the times of field polarity reversal over at least one of said periods of positive and negative current in said solenoid source to obtain field strength parameters; and

    using said field strength parameters and the said solenoid source strength parameter to determine the distance between said solenoid source and said sensor.

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