Removal of co-frequency powerline harmonics from multichannel surface NMR Data

J.J. Larsen, L. Liu, D. Grombacher, E. Auken

Publikation: Bidrag til bog/rapport/konferenceproceedingsKonferenceartikel i proceedingspeer review

1 Citationer (Scopus)

Abstrakt

Powerline harmonics is often the dominant noise source in surface NMR data and can completely overwhelm the NMR signal. Several methods have been successfully implemented for removal of powerline harmonics including notch filtering, multichannel filtering and model-based subtraction. However, the performance of these methods can be problematic when one of the powerline harmonic components has a frequency close to or coincident with the Larmor frequency, referred to as a co-frequency harmonic. Removal of the co-frequency harmonic can distort the NMR signal causing erroneous estimates of water content and relaxation rates. To solve this problem we propose an extended method of multichannel model-based subtraction of powerline harmonics. In this method, the co-frequency component is modeled in the primary coil and a reference coil on noise-only data recorded immediately prior to the NMR excitation. The phase and amplitude relationships between the components measured in the two coils are calculated. The relationships are used to predict the co-frequency harmonic component parameters in the primary coil during the NMR decay based on NMR signal free, synchronously recorded reference coil data. The mathematical framework is developed and we give examples of the efficiency of the method based on synthetic NMR signals embedded in noise-only data.

OriginalsprogEngelsk
Titel23rd European Meeting of Environmental and Engineering Geophysics
ForlagEuropean Association of Geoscientists and Engineers, EAGE
Antal sider5
ISBN (Elektronisk)9789462822238
DOI
StatusUdgivet - 3 sep. 2017
Udgivet eksterntJa
Begivenhed23rd European Meeting of Environmental and Engineering Geophysics - Malmo, Sverige
Varighed: 3 sep. 20177 sep. 2017

Publikationsserier

Navn23rd European Meeting of Environmental and Engineering Geophysics

Konference

Konference23rd European Meeting of Environmental and Engineering Geophysics
Land/OmrådeSverige
ByMalmo
Periode3/09/177/09/17

Programområde

  • Programområde 2: Vandressourcer

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