Patent ID: 6366089
Filing Date: 2002-04-02
Classification: G01N,G01R,G01V

Abstract:
Apparatus for nuclear magnetic resonance logging that is mountable in a drill string for logging of formations surrounding a borehole, comprising:a tubular drill collar having a generally cylindrical inner surface having an inner diameter and a generally cylindrical outer surface having an outer diameter; first means in said drill collar for producing a first magnetic field; second means in said drill collar for producing a second magnetic field; and means in said drill collar for receiving nuclear magnetic resonance signals from an investigation region in the formations; said second means comprising an antenna disposed in a recess spanning an axial extent in said outer cylindrical surface, the outer surface of said drill collar having a diameter that is reduced from said outer diameter over the axial extent of said recess, and the inner surface of said drill collar having a diameter that is not substantially reduced from said inner diameter over the axial extent of said recess.