5.2 MWD Magnetic Spacing

Clearly, if we are to make use of magnetic sensors in an MWD tool, we need to ensure that there is sufficient magnetic isolation to avoid significant magnetic influences from the other drilling equipment.

*The following explanation is included courtesy of Dr Steve Grindrod of Copsegrove Developments Ltd.
NON-MAGNETIC DRILL COLLAR LENGTH REQUIREMENTS
This section describes the theoretical background to drillstring magnetic interference, explains the origin of NMDC charts and makes recommendations on NMDC usage and inspection. This is based on [Reference CUR 252] (SPE 11382 by S.J. Grindrod and C.J.M. Wolff on Calculating NMDC length).