Downhole calibration system for directional sensors

Details Downhole calibration system for directional sensors Downhole calibration system for directional sensors

2005-11-22

2005-11-22

Raevis, Robert (Department: 2856)

Measuring and testing

Instrument proving or calibrating

Angle, direction, or inclination

Reexamination Certificate

active

06966211

ABSTRACT:
A method and apparatus is disclosed for improving the accuracy of directional surveys using magnetometers and accelerometers. The method corrects errors in bias, scale-factor, misalignment of cross-axial magnetometers, and bias or scale-factor of axial magnetometer by requiring the magnitude of measured cross-axial magnetic field to be as constant as possible over several tool face angles at a survey point in a wellbore and the magnitude of the measured total magnetic field and dip angle equal to the reference values, respectively. The axial component of the measured magnetic field is also determined. The method also corrects accelerometers similarly. The calibration parameters obtained at one survey point are applied to measurements at other survey points to improve the accuracy of surveys and the efficiency of drilling operations.

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R. Estes and P. Walters. Improvement of Azimuth Accuracy by Use of Iterative Total Field Calibration Technique and Compensation for System Environment Effects: SPE Article 19546. 64th Annual Technical Conference, Oct. 1989.
UK Patent Office Search Report dated May 17, 2004.

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