Pulse sequences and interpretation techniques for NMR measurements

An NMR borehole logging method for measuring an indication of petrophysical attributes of an earth formation, the method comprising the steps of:

• (a) applying in a pre-determined sequence at least two short NMR pulse trains, each pulse train comprising at least one pulse and resulting in at least one response signal from said earth formation, the interval T.sub.s between any two short pulse trains being less than the time required for polarization of substantially all nuclear magnetization in any bulk fluid contained in said earth formation;
• and
• (b) stacking NMR response signals from said at least two short NMR pulse trains to obtain time domain data indicative of fast decay components of a fluid state contained in said earth formation;
• (c) combining said at least two short NMR pulse trains with regular Carr-Purcell-Meiboom-Gill (CPMG) pulse-echo measurements of said earth formation, wherein a regular CPMG pulse-echo train is preceded by a recovery time T.sub.w sufficient to substantially polarize all nuclear magnetization in the fluid state;
• and
• (d) determining overall relaxation properties of the fluid state contained in said earth formation from the combination of said least two short NMR pulse trains with said regular CPMG pulse-echo measurements.

An NMR method for measuring an indication of an attribute of a volume of earth formation in a borehole, comprising the steps of:

• a) applying oscillating magnetic fields according to a pre-specified pulse sequence, said pulse sequence comprising:
• a regular Carr-Purcell-Meiboom-Gill (CPMG) train having between about 100 and 10,000 echoes, followed by at least one short wait interval T.sub.s of approximately 10-100 ms duration, followed next by at least one short CPMG train having between about 1 and 100 echoes;
• b) measuring NMR signals representing spin-echo relaxation of a population of particles in the geologic structure;
• and
• c) processing NMR signals corresponding to said regular CPMG train and NMR signals corresponding to said at least one short CPMG train to determine values for the magnetic resonance effective porosity (.PHI..sub.MRE) of the volume of the earth formation and values for the clay-bound porosity .PHI..sub.CIB of the volume of the earth formation.