| 摘要 |
<p>A NMR measurement-while-drilling tool has a permanent magnet (12) with a magnetic field direction substantially perpendicular to the axis of the borehole (36), a steel collar (10) of a non-magnetic material surrounding the magnet, antenna (14) positioned outside the collar, and a soft magnetic material positioned in a predetermined relationship with the collar and the magnet that helps to shape the magnetic field of the tool.</p> |
