SNMR signal contribution in conductive terrains

Abstract

To correctly invert and interpret Surface Nuclear Magnetic Resonance (SNMR) data collected in conductive terrains, an accurate estimate of subsurface conductivity structure is required. Given such an estimate, it would be useful to determine, before conducting an SNMR sounding, whether or not the conductivity structure would prevent groundwater being detected. Here we use synthetic data to find the maximum depth at which water can be detected and the depth range from which most of the SNMR signal originates in conductive halfspaces. Using these parameters it is shown that, for coincident loop SNMR soundings, increasing loop dimensions does not significantly improve depth penetration. It is also shown that the results can be used with halfspace approximations of more complicated conductivity structures to give a reasonable estimate of the depth range over which signal is obtainable in conductive terrains.