Overview:
- Inaccuracies in the theoretical values of Btotal and Dip can be determined provided that there is sufficient turn and/or build
- Technique has been verified both theoretically and by comparison with IFR measurements
- Method can be used to correct survey data or advise of potential inaccuracies in local magnetic field parameters
- Method can be used to corroborate IFR values Gyro survey comparison would be needed for quantification of declination offset
Calculating Offsets in the Magnetic Field
• Offsets in the local theoretical values of Btotal and dip angle can be calculated from downhole sensor data
• Requires changes in inclination and azimuth
• Uses all the survey data
• Can be applied even if survey data affected by drill string interference
• 2 examples presented showing good correlation between calculated offsets and observed offsets
• Reconstituted values of Btotal and dip can be calculated from the final azimuth
• Difference between these values and the theoretical magnetic field values can be
expressed as a function of attitude and location
• Offsets in Btotal and dip can be determined by combining all data (e.g least squares) at varying inclination/azimuth angles
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View the entire Presentation:
Calculating Offsets In Local Magnetic Field Parameters
Anne Holmes and Ian Mitchell - Halliburton