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Method of assessing positional uncertainty in drilling a well

  • US 6,834,732 B2
  • Filed: 06/06/2002
  • Issued: 12/28/2004
  • Est. Priority Date: 12/08/1999
  • Status: Expired due to Term
First Claim
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1. A method of estimating positional uncertainty in drilling a well, comprising:

  • supplying a first set of values representing a first three-dimensional uncertainty of the actual position of a drill bit with respect to the estimated position thereof;

    supplying a second set of values representing a second three-dimensional uncertainty of the actual position of a geological feature with respect to the estimated position thereof;

    combining the first and second sets of values to form a third set of values representing a third uncertainty of the position of the drill bit with respect to the geological feature;

    calculating from the third uncertainty the probability that the drill bit reaches a predetermined position relative to the geological feature;

    defining at least one geological target as a finite surface relative to the geological feature; and

    correcting at least one value in the first set of values using information from a marker point whose relative position including positional uncertainty to the at least one geological target is at least partly known.

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