RARE EARTH ALLOYS AS BOREHOLE MARKERS

A magnetic marking method includes drilling a borehole and marking a position along an uncased section of the borehole with a magnetic marker comprising a magnetic rare earth alloy. A magnetic marker for open hole use includes an unconsolidated mass of high remanence, magnetized material that comprises a magnetic rare earth alloy. The magnetic marker for open hole use also includes a suspension fluid suited for conveying the magnetized material through a drill string bore into an open borehole. A magnetic marker for a casing terminus includes a magnet comprising a magnetic rare earth alloy and an attachment mechanism that secures the magnet to a casing shoe. Such magnetic markers for open hole use or a casing terminus can be used for borehole intersection operations.