Experimental Verification of Advanced SNMR Modeling

Whatever would be the practical implementation of Surface Nuclear Magnetic Resonance (SNMR) survey, inversion is based on forward modeling of the magnetic resonance response. Consequently, the mathematical model is a crucial point for inversion. We have developed advanced mathematical model that allows computing magnetic resonance signal from 3D targets both in FID (free induction decay) and SE (spin echo) modes. This model takes into account both time and lateral variations of the earth’s magnetic field, water temperature and electrical resistivity of the subsurface but also the effect of magnetic rocks on MRS signal. For experimental verification of the modeling routine we used two bulk water reservoirs. One-dimensional (1-D) measurements were performed in winter from the ice surface in the Baltic Sea (Sweden) and 3-D verification was made using an artificial water pool located in the southern part of the New Caledonia Island. Modeling was carried out taking into account reservoir geometry and local conditions obtained from independent measurements. We have found a good correspondence between observed and theoretical signals for both FID and SE measurements. At our knowledge, SNMR modeling was never compared with field data obtained under all mentioned above conditions.