What Does Non-Mag (NMDC) Mean?
Non-mag is a construction industry term commonly used instead of the full term "non-magnetic drill collars" (NMDC). Non-magnetic collars are used in every bottom hole assembly (BHA) involving magnetic surveys. The non-mag prevents the Earth's magnetic field from interfering with BHA parts that cannot degmagnetized. As the bottom hole assembly is an important aspect of a drill string in a drilling operation, non-magnetic drill collars are functionally essential.