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Rate gyro wells survey system including nulling system

DC
  • US 5,806,195 A
  • Filed: 06/17/1997
  • Issued: 09/15/1998
  • Est. Priority Date: 12/19/1994
  • Status: Expired due to Term
First Claim
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1. A method of performing a survey of a well borehole comprising the steps of:

  • (a) positioning within a well borehole an elongate sonde having a rate gyro therein rotating about an axis and forming an output indicative of north, wherein said rate gyro is supported by a housing rotatable between first and second positions separated by 180°

    of housing rotation, and(i) a first output indicative of north comprises N measurements is determined at said first sonde position,(ii) said housing is then rotated by 180° and

    a second output indicative of north comprising another N measurements is determined at said second sonde position, and(iii) N is an integer;

    (b) combining said first and second outputs indicative of north to yield a measure of north in which systematic instrument error is reduced;

    (c) positioning the sonde at spaced locations along a well borehole; and

    (d) repeating step a) at each said spaced location.

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