Method of imaging using azimuthally resolved NMR while drilling

A nuclear magnetic resonance (NMR) sensor comprising:

• a magnet assembly having a first end piece magnet and a second end piece magnet, wherein the magnet assembly creates a static magnetic field;
• and
• a first transversal-dipole antenna having an azimuthally selective response function in a selectable azimuthal aperture to generate a radio frequency (RF) magnetic field;
• the NMR sensor configured to:
• determine sequence excitation parameters of a first azimuthally selective NMR excitation that include a train length, a train repetition time, and a number of trains, wherein the sequence excitation parameters are selected based on an azimuthal position of the selectable azimuthal aperture and rotation of the NMR sensor;
• initiate the first azimuthally selective NMR excitation in at least one sensitivity region at a first frequency using the selectable azimuthal aperture and the magnet assembly, wherein the at least one sensitivity region is determined by the static magnetic field and the RF magnetic field;
• and
• acquire one or more azimuthally selective NMR signals at the first frequency using the selectable azimuthal aperture.

A system comprising:

• a nuclear magnetic resonance (NMR) sensor comprising:
• a magnet assembly to create a static magnetic field, and
• a first transversal-dipole antenna having an azimuthally selective response function in a selectable azimuthal aperture to generate a radio frequency (RF) magnetic field;
• a processor;
• and
• one or more non-transitory machine-readable media having program code executable by the processor to cause the NMR sensor to:
• determine sequence excitation parameters of a first azimuthally selective NMR excitation that include a train length, a train repetition time, and a number of trains, wherein the sequence excitation parameters are selected based on an azimuthal position of the selectable azimuthal aperture and rotation of the NMR sensor;
• initiate the first azimuthally selective NMR excitation in at least one sensitivity region at a first frequency using the selectable azimuthal aperture and the magnet assembly, wherein the at least one sensitivity region is determined by the static magnetic field and the RF magnetic field;
• and
• acquire one or more azimuthally selective NMR signals at the first frequency using the selectable azimuthal aperture.