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Incorporation of a 3-D lossy (conductive) Earth into Surface NMR Tomography
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, Near Surface 2010 - 16th EAGE European Meeting of Environmental and Engineering Geophysics, Sep 2010, cp-164-00124
- ISBN: 978-90-73781-88-7
Abstract
The surface nuclear magnetic resonance (NMR) tomography technique uses electromagnetic (EM) fields to locate and quantify groundwater occurrences. The magnetic fields interact with the spin magnetic moments of water protons situated within the static Earth’s magnetic field. In conventional surface-NMR forward and inverse modeling, semi-analytical solutions for the electromagnetic fields on a layered earth are employed. This simplification restricts the model to regular loop shapes on a flat terrain and 1-D conductivity distributions. To remove such limitations and to extend the analysis to rough terrain (e.g. mountainous regions) and 3-D heterogeneous media incorporating conductive (lossy) zones (e.g. clay lenses), we have developed a hybrid electromagnetic modeling scheme that combines integral equations with the finite-element method. Local mesh refinement enables the sensitivity function to be sampled in an appropriate manner near the principal singularity (i.e. the transmitter). Here, we apply the novel numerical forward and inverse modeling scheme to synthetic data to illustrate its effectiveness.