Research Project
Laboratory and Numerical Studies of the NMR Response of Near-Surface Materials
The Problem
Surface and logging NMR can be used to obtain information about pore-scale properties that govern the storage and flow of water. Of specific interest in our research are the NMR relaxation time, which can be measured with logging and surface NMR, and the diffusion coefficient of the pore water which can be measured with logging NMR. These two parameters are related to the surface-area-to-volume ratio of the pore space, an estimate of which can be used to determine permeability or hydraulic conductivity. Questions remain, however, about the interpretation of these NMR measurements in unconsolidated or weakly consolidated aquifer materials.
Our Approach
We investigate the NMR response of materials through numerical modeling and laboratory experiments. Numerical modeling is conducted on grain packs where the physical and chemical parameters are easily assigned and we are able to simulate the NMR measurement. Laboratory measurements are made on well-characterized samples where we can control and/or determine the relevant physical and chemical properties. In the laboratory, by varying the amount of iron coating on the surface of the samples, we are able to vary the strength of the surface relaxation parameter, which controls the link between NMR relaxation measurements and permeability/hydraulic conductivity. We are also analyzing samples from a variety of near-surface sites to understand the natural variability in surface relaxivity and its influence on the NMR measurements. Samples with a range of magnetic grain content are being used to explore the effect of internal magnetic field gradients on NMR diffusion measurements.
It is commonly assumed, in the interpretation of NMR relaxation data, that one pore space is sampled in the time-scale of the experiment.
Project Lead/Contact
Emily Fay, Katherine Dlubac, Rosemary Knight
Project Collaborators
Elliot Grunewald (Vista Clara, Inc.), David Walsh (Vista Clara, Inc.), Kristina Keating (Rutgers University)
Project Products
- Dlubac, K.I., and R.J. Knight (in prep) A laboratory study of the relationship between NMR relaxation and permeability in sands.
- Dlubac, K.I., R.J. Knight, K. Keating (2013) A numerical study of the relationship between NMR relaxation and permeability in materials sands and gravels, Near Surface Geophysics, Magnetic Resonance in the Subsurface Special Issue, in review
- Dlubac, K., and R. Knight (2012), A numerical study of the relationship between NMR relaxation and permeability in materials with large pores, in the 5th Intervational Workshop on Magnetic Resonance in the Subsurface, 25-27 Septermber, Hannover, Germany.
- Grunewald, E. and R. Knight (2011) A laboratory study of NMR relaxation times in unconsolidated heterogeneous sediments, Geophysics, 76, No. 4 G73-G83, doi: 10.1190/1.3581094
- Grunewald, E. and R. Knight (2011) The effect of pore size and magnetic susceptibility on the surface NMR relaxation parameter T2*, Near Surface Geophysics, 9, No. 2, 169-178, doi:10.3997/1873-0604.2010062
- Grunewald, E and R. Knight (2009) A laboratory study of NMR relaxation times and pore coupling in heterogeneous media, Geophysics, 74, E215, doi:10.1190/1.3223712.
- Grunewald, E., and Knight, R., Estimating pore properties from NMR relaxation time measurements in heterogeneous media, Eos Trans. AGU, 89(53), Fall Meet. Suppl., POSTER, 2008. (Winner of AGU Outstanding Student Presentation Award in Near-Surface Geophysics)
