One possible source of error in magnetic surveys is ill based charts used for selecting the required length of non-magnetic drill collar (NMDC). Based on theoretical considerations and measurements of pole- strength values in the field, well-defined charts can be constructed for the selection of the minimum required NMDC length for a specific bottom hole assembly and acceptable azimuth error.

Keywords:
drill-string magnetisation, pole strength, compass, magnetisation, drillstring design, drill string, erroneous magnetic field, stabiliser, azimuth error, nmdc length
Subjects:
Drillstring Design, Drilling Equipment
Copyright 1983, IADC/SPE Drilling Conference
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