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Journal Articles AIP Conference Proceedings Year : 2011

Large-Scale NMR Measurements in Porous Media

A. Legchenko
  • Function : Author
J.M. Vouillamoz
  • Function : Author

Abstract

The large-scale Nuclear Magnetic Resonance measurements in the Earth's magnetic field (Surface NMR method) is a geophysical technique that allows non-invasive investigations of water-saturated rocks. The measuring setup consists of a wire loop on the surface that is energized by one or two pulses of oscillating current. After the pulses are cut off, the free induction decay (FID) and/or the spin echo (SE) signal from groundwater could be measured. SNMR results are averaged over the investigated volume that depends on the loop size and typically varies from 20x20x20 to 100x100x100 cubic meters. The maximum depth of groundwater detection can vary from 45 to 150 m depending on measurement conditions, although an average depth of investigation is generally considered to be about 100 m. Our recent results show that combination of FID and SE allows rendering the SNMR less dependent on the geological conditions. Because of different scales, use of rock samples for calibration of the SNMR-estimate of the water content is difficult or impossible. Thus, for interpretation of experimental data we use a mathematical model that allows computing the theoretical signal generated by groundwater. The processing of SNMR data can provide the depth, thickness and water content of investigated aquifers. For improving accuracy of the SNMR results we use calibration based on borehole pumping test data. Based on the water content and the relaxation time provided by MRS it is possible to estimate the aquifer's hydrodynamic properties.

Domains

Geomorphology
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Dates and versions

insu-00648764 , version 1 (06-12-2011)

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A. Legchenko, J.M. Vouillamoz. Large-Scale NMR Measurements in Porous Media. AIP Conference Proceedings, 2011, 1330, pp.47-50. ⟨10.1063/1.3562230⟩. ⟨insu-00648764⟩
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