Permanent magnet configuration for NMR logging tool

A method, comprising:

• moving a nuclear magnetic resonance (NMR) logging tool through a wellbore extending into a formation;
• establishing a static magnetic field within an antenna window of a radio frequency (RF) antenna of the NMR logging tool, via a first permanent magnet, a second permanent magnet, and a third permanent magnet disposed within the NMR logging tool, wherein the first, second, and third permanent magnets are disposed at different longitudinal positions along the NMR logging tool, wherein the second permanent magnet is located between the first permanent magnet and the third permanent magnet, and wherein the RF antenna is disposed proximate and at approximately the same longitudinal position as the first permanent magnet;
• establishing a region of interest via the static magnetic field in the antenna window;
• exciting nuclei of the formation in the region of interest via RF pulses produced by the RF antenna;
• detecting one or more signals from excited nuclei within the antenna window via the RF antenna;
• establishing an attractive force between a first side of the NMR logging tool and a casing in the wellbore via the first and second permanent magnets;
• and
• establishing an opposing attractive force between a second side of the NMR logging tool opposite the first side and the casing via the third permanent magnet.

A nuclear magnetic resonance (NMR) logging tool for use in a wellbore, comprising:

• a first permanent magnet disposed at a first longitudinal position within the NMR logging tool;
• a radio frequency (RF) antenna disposed proximate the first permanent magnet at the first longitudinal position for detecting signals from excited nuclei within an antenna window of examination;
• a second permanent magnet disposed at a second longitudinal position within the NMR logging tool;
• and
• a third permanent magnet disposed at a third longitudinal position within the NMR logging tool;
• wherein the second permanent magnet is located between the first permanent magnet and the third permanent magnet in a direction of a longitudinal axis of the NMR logging tool;
• wherein the first and second permanent magnets are disposed immediately adjacent each other, and wherein the third permanent magnet is spaced from the second permanent magnet in the direction of the longitudinal axis.