×

Method to assess uncertainties and correlations resulting from multi-station analysis of survey data

  • US 10,228,987 B2
  • Filed: 02/28/2013
  • Issued: 03/12/2019
  • Est. Priority Date: 02/28/2013
  • Status: Active Grant
First Claim
Patent Images

1. A method of a drilling a borehole, comprising:

  • obtaining errors associated with multi-station survey measurements obtained at a drill string in the borehole;

    partitioning the obtained errors into a set of magnetometer bias errors and a set of measurement errors including scale factor errors;

    determining a post-fit covariance matrix for the magnetometer bias errors that includes the effects of the measurement errors on the magnetometer bias errors;

    determining an ellipsoid of constant probability for the post-fit covariance matrix, wherein the ellipsoid of constant probability defines an uncertainty in trajectory of the drill string;

    comparing the ellipsoid of constant probability for the post-fit covariance matrix to the ellipsoid of constant probability for a standard error model;

    when the ellipsoid of constant probability for the post-fit covariance matrix is less than the ellipsoid of constant probability for the standard error model, determining an ellipsoid of constant probability for a target error model based on reducing magnetometer bias errors and scale factor errors of the standard error model, the ellipsoid of constant probability for the target error model being bound by the ellipsoid of constant probability for the post-fit covariance matrix;

    correcting a trajectory of the drill string using the target error model; and

    steering the drill string in the borehole using the corrected trajectory.

View all claims
  • 1 Assignment
Timeline View
Assignment View
    ×
    ×