The magnetic survey instrument is influenced by the presence of a magnetic field around the tool: ferromagnetic material in the formation, drill pipe, drill collar, or other bottom hole assemblies. This influence can’t be completely eliminated, but can be reduced to minimize interference with the earth’s magnetic field. The survey instrument is placed inside a non-magnetic drill collar so that the survey instrument can measure the earth’s magnetic field. More than one non-magnetic drill collar may be used to minimize magnetic interference from the drill string and bottom hole assembly.
Post time: Feb-27-2023