This paper presents four linked results that lead to better permeability estimation from borehole NMR measurements: 1. Longitudinal relaxation parameters can be used to estimate permeability more successfully than has been shown in the literature; 2. the requisite longitudinal relaxation parameters can be estimated from borehole waveforms recorded for a range of polarizing pulse durations, by a method which fits one or more models simultaneously to the entire set of recorded waveforms; 3. the small number of parameters of the stretched-exponential model means that longitudinal relaxation parameters can be extracted more robustly in the presence of noise than when using a two-exponential model; 4. the authors propose a new representation for the NMR properties of rocks, namely the stretched-exponential form. This form describes laboratory measurements of the longitudinal relaxation of water-saturated rocks. The stretched-exponential representation is very convenient because of its compactness - three parameters. A mathematical derivation of the stretched-exponential form is given, based on a distribution of single relaxation times which is weighted toward short times.
|Original language||English (US)|
|State||Published - Dec 1 1986|
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