Patent ID: 7034529

Claim:
A method of evaluating an earth formation using a nuclear magnetic resonance (NMR) device conveyed within a borehole penetrating said formation, comprising: (a) producing a static magnetic field in a volume of said earth formation and aligning nuclear spins therein; (b) pulsing the earth formation with at least one sequence of radio frequency (RF) pulses, said at least one RF pulse sequence comprising: (A) an excitation pulse with a tip angle substantially equal to 90°; (B) a plurality of groups of refocusing pulses, each group comprising a phase-alternated pair of refocusing pulses, one pulse of said phase-alternated pair having a phase substantially equal to a phase of said excitation pulse; (c) obtaining a plurality of spin echo signals in response to application of said at least one pulse sequence of RF pulses; and (d) processing said spin echo signals to give corrected spin echo signals in which a DC offset has been reduced.