TY - JOUR

T1 - Inverting surface NMR free induction decay data in a voltage-time data space

AU - Grombacher, Denys

AU - Liu, Lichao

AU - Kass, Mason Andrew

AU - Osterman, Gordon

AU - Fiandaca, Gianluca

AU - Auken, Esben

AU - Larsen, Jakob Juul

PY - 2020

Y1 - 2020

N2 - Envelope detection is an integral step of the surface NMR data processing workflow. A promising approach to produce high signal-to-noise ratio envelopes involves a scheme referred to as spectral analysis (SA) envelope detection – a scheme based upon a series of discrete Fourier transforms for sliding windows of observed NMR data. This method has the advantage that it naturally handles the narrow-band character of the NMR signal without corrupting the early portion of the time-series – both of which are challenges confronting traditional surface NMR processing schemes. However, SA estimated envelopes are weighted by the NMR relaxation time during processing and the envelopes have units of volt-seconds, whereas the unit of the data space employed by traditional surface NMR forward models is volts. To better integrate the SA envelope detection scheme within the surface NMR workflow, we propose to modify the surface NMR forward model such that it predicts data directly in the voltage-time data space. Synthetic and field data inversions, as well as a parameter resolution study, are presented to demonstrate advantages of pairing the SA envelope detection scheme with a forward model that works in the voltage-time data space. The method is shown to improve parameter resolution and does not require significant modifications to existing surface NMR inversion platforms.

AB - Envelope detection is an integral step of the surface NMR data processing workflow. A promising approach to produce high signal-to-noise ratio envelopes involves a scheme referred to as spectral analysis (SA) envelope detection – a scheme based upon a series of discrete Fourier transforms for sliding windows of observed NMR data. This method has the advantage that it naturally handles the narrow-band character of the NMR signal without corrupting the early portion of the time-series – both of which are challenges confronting traditional surface NMR processing schemes. However, SA estimated envelopes are weighted by the NMR relaxation time during processing and the envelopes have units of volt-seconds, whereas the unit of the data space employed by traditional surface NMR forward models is volts. To better integrate the SA envelope detection scheme within the surface NMR workflow, we propose to modify the surface NMR forward model such that it predicts data directly in the voltage-time data space. Synthetic and field data inversions, as well as a parameter resolution study, are presented to demonstrate advantages of pairing the SA envelope detection scheme with a forward model that works in the voltage-time data space. The method is shown to improve parameter resolution and does not require significant modifications to existing surface NMR inversion platforms.

KW - INVERSION

KW - MRS

KW - NOISE

KW - NUCLEAR-MAGNETIC-RESONANCE

KW - SOFTWARE

UR - http://www.scopus.com/inward/record.url?scp=85074993577&partnerID=8YFLogxK

U2 - 10.1016/j.jappgeo.2019.103869

DO - 10.1016/j.jappgeo.2019.103869

M3 - Journal article

AN - SCOPUS:85074993577

VL - 172

JO - Journal of Applied Geophysics

JF - Journal of Applied Geophysics

SN - 0926-9851

M1 - 103869

ER -