Simultaneous Gaussian and exponential inversion for improved analysis of shales by NMR relaxometry

K.E. Washburn, E. Anderssen, Sarah Vogt, J.D. Seymour, J.E. Birdwell, C.M. Kirkland, S.L. Codd

    Research output: Contribution to journalArticle

    19 Citations (Scopus)

    Abstract

    © 2014 Elsevier Inc. All rights reserved. Nuclear magnetic resonance (NMR) relaxometry is commonly used to provide lithology-independent porosity and pore-size estimates for petroleum resource evaluation based on fluid-phase signals. However in shales, substantial hydrogen content is associated with solid and fluid signals and both may be detected. Depending on the motional regime, the signal from the solids may be best described using either exponential or Gaussian decay functions. When the inverse Laplace transform, the standard method for analysis of NMR relaxometry results, is applied to data containing Gaussian decays, this can lead to physically unrealistic responses such as signal or porosity overcall and relaxation times that are too short to be determined using the applied instrument settings. We apply a new simultaneous Gaussian-Exponential (SGE) inversion method to simulated data and measured results obtained on a variety of oil shale samples. The SGE inversion produces more physically realistic results than the inverse Laplace transform and displays more consistent relaxation behavior at high magnetic field strengths. Residuals for the SGE inversion are consistently lower than for the inverse Laplace method and signal overcall at short T2 times is mitigated. Beyond geological samples, the method can also be applied in other fields where the sample relaxation consists of both Gaussian and exponential decays, for example in material, medical and food sciences.
    Original languageEnglish
    Pages (from-to)7-16
    JournalJournal of Magnetic Resonance
    Volume250
    DOIs
    Publication statusPublished - 2015

    Fingerprint

    shales
    Inverse transforms
    Laplace transforms
    Magnetic Resonance Spectroscopy
    Porosity
    Nuclear magnetic resonance
    inversions
    nuclear magnetic resonance
    Oil shale
    Fluids
    Lithology
    Petroleum
    Relaxation time
    Pore size
    Hydrogen
    porosity
    Magnetic fields
    decay
    Food Technology
    shale oil

    Cite this

    Washburn, K. E., Anderssen, E., Vogt, S., Seymour, J. D., Birdwell, J. E., Kirkland, C. M., & Codd, S. L. (2015). Simultaneous Gaussian and exponential inversion for improved analysis of shales by NMR relaxometry. Journal of Magnetic Resonance, 250, 7-16. https://doi.org/10.1016/j.jmr.2014.10.015
    Washburn, K.E. ; Anderssen, E. ; Vogt, Sarah ; Seymour, J.D. ; Birdwell, J.E. ; Kirkland, C.M. ; Codd, S.L. / Simultaneous Gaussian and exponential inversion for improved analysis of shales by NMR relaxometry. In: Journal of Magnetic Resonance. 2015 ; Vol. 250. pp. 7-16.
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    Simultaneous Gaussian and exponential inversion for improved analysis of shales by NMR relaxometry. / Washburn, K.E.; Anderssen, E.; Vogt, Sarah; Seymour, J.D.; Birdwell, J.E.; Kirkland, C.M.; Codd, S.L.

    In: Journal of Magnetic Resonance, Vol. 250, 2015, p. 7-16.

    Research output: Contribution to journalArticle

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