Overview:
• Error terms model permanent magnetization
• Fixed value term contributes uncertainty even at north/south
• Arbitrary term values
– Therefore BHA must be evaluated for compliance with model Therefore BHA must be evaluated for compliance with model
• Weighting function models attitude sensitivity
DrillString Interference
• ISCWSA terms ISCWSA terms
– Uncertainty is not location dependent
– Therefore spacing requirement is location dependent
• Alternative term
– Uncertainty is location dependent
– Therefore sp gq acin requirement is not location dependent
– Compliance more likely?
• Single spacing option is restrictive
• Survey QC tests should include model Survey QC tests should include model s’ DSI contribution DSI contribution
• ISCWSA terms result in QC tests that catch out ISCWSA terms result in QC tests that catch out-of-spec Az spec Az, but not out-of-spec condition
• ISCWSA terms reduce QC sensitivity at low inc and N/S
• QC tests derived from alternative term catch out-of-spec condition but can trip with insignificant Az error condition, but can trip with insignificant Az error
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Drillstring Magnetic Interference
Harry Wilson - Baker Huges Incorporated