Advancing Magnetic Resonance Geophysical Methods to Characterize Groundwater Systems

Magnetic resonance geophysical methods allow efficient in-situ characterization of key hydrogeologic properties including porosity, pore size, permeability, and specific yield. Precise downhole measurements can be carried out with small-diameter borehole tools and non-invasive profiling can be achieved using multi-channel surface instrumentation. Recent hardware advancements have focused on accelerating measurements speed, reducing impacts of near-borehole disturbance, and reducing hardware cost. These advancements have enabled use of borehole and surface magnetic resonance across a wider range of environmental and geologic conditions, with applications in water resources, environmental remediation, engineering, and mining. In addition to characterization of static hydrogeologic properties, we have recently investigated methodologies to characterize dynamic systems. Extending from advanced techniques in medical MRI, we have tested implementation of magnetic resonance measurements that are synchronized with fluid injection. These experiments aim to determine dynamic parameters including flow velocity, flow distribution, and dispersion. Meso-scale laboratory experiments in a PVC flow cell have yielded promising results indicating the ability to characterize flow inside the formation both qualitatively and quantitatively. Dynamic experiments on unnsaturated systems undergoing drying also demonstrate the capability to monitor fractionation of water between different pore sizes as saturation decreases. Field implementation of these flow injection methods will combine borehole magnetic resonance measurements with specially designed packer systems.