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Gyroscopic steering tool using only a two-axis rate gyroscope and deriving the missing third axis

  • US 7,813,878 B2
  • Filed: 04/12/2007
  • Issued: 10/12/2010
  • Est. Priority Date: 08/07/2003
  • Status: Expired due to Fees
First Claim
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1. A method of compensating measurements made by a downhole survey instrument, the method comprising:

  • (a) making measurements with the downhole survey instrument at a plurality of rotational positions;

    (b) using a processor to;

    (i) apply first correction to said measurements using a thermal model to give a first set of corrected measurements;

    (ii) fit a sinusoidal function of angular position to said first set of corrected measurements;

    (iii) fit a polynomial function of temperature to a residual remaining after said sinusoidal fitting; and

    (iv) determine a corrected bias for said measurements made by the downhole gyroscope using results of said polynomial fitting.

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