The Interpretation of Nuclear Magnetic Resonance Measurements in Near-Surface Geophysics

The nuclear magnetic resonance (NMR) measurement is unique in geophysics because it is the only method that can directly detect hydrogen in water and hydrocarbons and is sensitive to its physiochemical environment. Traditionally used in petroleum exploration, NMR is of growing interest for near-surface applications. In the near surface, NMR measurements are collected using a well-logging instrument or a surface-based instrument that can detect water at depths of ~100 m’s and are primarily used to evaluate groundwater resources.

 Laboratory studies have been used to determine relationships between the physical and chemical properties of geologic material and the NMR measurement. As early as the 1960’s laboratory studies showed that NMR measurements can be used to determine pore-size distribution and estimate permeability in petroleum reservoirs, and such measurements have been adapted in the near surface to estimate the hydraulic conductivity of aquifers. However, the full potential of the NMR measurement for near-surface applications is far from realized.  Recent laboratory research has demonstrated the use of NMR measurements to detect hydrocarbons in soils even at low hydrocarbon concentrations, to monitor microbially induced changes in chemistry and pore volumes of soils, and monitor abiotic chemical reactions associated with contaminant remediation. This presentation will highlight these and other new laboratory studies that demonstrate the potential uses of NMR for hydrogeo- and biogeophysics applications.