System for logging a well during the drilling thereof

A method of using nuclear magnetic resonance logging apparatus for effecting the geophysical examination of a bore hole having a longitudinal axis, said logging apparatus having a longitudinal axis substantially aligned with the longitudinal axis of the bore hole and a means for generating a radio frequency magnetic field, said method comprising:

• (a) coupling said logging apparatus to a drilling apparatus having a drill bit mounted on a drill collar extending through the bore hole such that said means for generating the radio frequency magnetic field is located outside said drill collar for rotational and longitudinal movement therewith,
• (b) forming a bore hole by rotating said drill bit, and
• (c) operating said logging apparatus to:
• (1) generate a static magnetic field in the region of a portion of the bore hole adjacent said logging apparatus, which region includes materials sought to be analyzed,
• (2) generate a radio frequency magnetic field substantially symmetric about the longitudinal axis of the logging apparatus to excite nuclei of the materials sought to be analyzed in said region, and
• (3) receive nuclear magnetic resonance signals from the excited nuclei for providing an output signal indicative of properties of the material sought to be analyzed.