Patent ID: 7301337
Filing Date: 2007-11-27
Classification: G01N,G01V

Abstract:
1. A method of estimating a property of interest relating to an earth formation comprising: (a) conveying a Nuclear Magnetic Resonance (NMR) logging tool into a borehole in said earth formation; (b) applying a first pulse sequence having a first associated measurement frequency and measuring first signals corresponding to said first pulse sequence, said first signals including non-NMR signals resulting from (A) an excitation pulse, and, (B) a refocusing pulse in said first pulse sequence; (c) applying a plurality of additional pulse sequences having associated additional frequencies different from each other and from said first frequency; (d) measuring additional signals resulting from applying said plurality of additional pulse sequences; (e) determining from said first and said additional measured signals an estimate of said property of interest, said estimate substantially unaffected by said non-NMR signals; and (f) recording the estimate of the property of interest on a suitable medium; wherein the first and the additional frequencies are related by an expression of the form where δf is a separation of frequencies, nf is the number of frequencies, m is any integer that is not a multiple of nf, and t is a time over which a phase difference evolves.