Interpretation of magnetic resonance soundings in rocks with high electrical conductivity

doi:10.1016/j.jappgeo.2008.04.002

Authors

Legchenko, Anatoly; Ezersky, Mikhail; Girard, Jean-Francois; Baltassat, Jean-Michel; Boucher, Marie; Camerlynck, Christian; Al-Zoubi, Abdallah + 3

Contributors

Laboratoire d'étude des transferts en hydrologie et environnement (LTHE); Observatoire des Sciences de l'Univers de Grenoble (OSUG); Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut National Polytechnique de Grenoble (INPG)-Centre National de la Recherche Scientifique (CNRS); Geophysical Institute of Israel; Bureau de Recherches Géologiques et Minières (BRGM) (BRGM); Structure et fonctionnement des systèmes hydriques continentaux (SISYPHE); Université Pierre et Marie Curie - Paris 6 (UPMC)-École Pratique des Hautes Études (EPHE); Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Mines Paris - PSL (École nationale supérieure des mines de Paris); Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS); Al-Balqa' Applied University; Engineering Faculty + 10

Publisher

HAL CCSD; Elsevier

Abstract

International audience ; Magnetic resonance sounding (MRS) is an electromagnetic method designed for groundwater investigations. MRS can be applied not only for studying fresh-water aquifers, but also in areas where intrusion of saline water is rendering the subsurface electrically conductive. In the presence of rocks with a high electrical-conductivity attenuation and a phase shift of the MRS signal may influence the efficiency of the MRS method. We investigated the performance of MRS for allowing us to propose a procedure for interpreting MRS data under these conditions. For numerical modeling, we considered a subsurface with a resistivity between 0.5 and 10 Ω m. The results show that the depth of investigation with MRS depends upon the electrical conductivity of groundwater and surrounding rocks, on the depth of the saline water layer, and on the amount of fresh water above the saline water. For interpreting MRS measurements, the electrical conductivity of the subsurface is routinely measured with an electrical or electromagnetic method. However, due to the equivalence problem, the result obtained with these methods may be not unique. Hence, we investigated the influence of the uncertainty in conductivity distribution provided by transient electromagnetic measurements (TEM) on MRS results. It was found that the uncertainty in TEM results has an insignificant effect on MRS.