Magnetometers for measurement-while-drilling applications

摘要

The method of drilling a borehole in an earth formation comprises the followings steps: conveying a plurality of magnetometers into the borehole on a bottomhole assembly, determining from outputs of the plurality of magnetometers an indication of a source of magnetic disturbance in proximity to the borehole, and controlling a direction of the drilling based on said indication. The apparatus for drilling a borehole in an earth formation comprises (a) a bottomhole assembly (BHA) including a drill bit, (b) at least two magnetometers positioned at substantially opposite sides of the BHA, (c) a processor on the BHA which: (A) determines from outputs of of the at least two magnetometers a magnetic field gradient, and (B) controls a drilling direction of the BHA based on the determined magnetic field gradient.