Estimation of Hydraulic Conductivity in Unconsolidated Near-Surface Aquifers Using NMR Geophysics
Estimation of Hydraulic Conductivity in Unconsolidated Near-Surface Aquifers Using NMR Geophysics
Presented on Wednesday, May 7, 2014
In this research, we investigated the use of surface and borehole nuclear magnetic resonance (NMR) geophysical measurements to estimate hydraulic conductivity (K) at sub-meter to several-meter resolution in unconsolidated near-surface aquifers. Co-located surface NMR, direct push (DP) NMR, and direct push permeameter (DPP) K measurements were performed over three geologically-distinct unconsolidated aquifers with varying degrees of magnetic mineralization. At each location, multiple co-located NMR and DPP K measurements were performed over lateral distances ranging up to 1000 meters. K estimates from DP NMR measurements were directly compared to DPP K measurements at 0.5-meter vertical intervals at all locations. Optimized NMR-K calibration coefficients computed at different sites within each geographical location varied by less than a factor of 3, and the root mean square deviation between DPP and DP-NMR K was approximately 0.64 orders of magnitude. A significant and unexpected finding was that a single set of fixed NMR calibration coefficients performed nearly as well (at matching the DPP-K measurements) as locally optimized NMR-K coefficients. The surface NMR measurements provided adequate resolution to identify the high-K and low-K sections of each aquifer. Optimized NMR-K estimates for the surface NMR Carr-Purcell Meiboom-Gill CPMG sequence closely matched the optimized DP NMR-K coefficients across all data sets. In contrast, the optimized NMR-K coefficients for the surface NMR free induction decay measurements varied by more than an order of magnitude over the three geographic regions, due to differences in magnetic mineralization among the three aquifer materials. Overall, the results indicate that existing NMR-K transforms, originally developed and used to estimate K in consolidate limestone and sandstone oil reservoirs, can be employed to estimate K in near-surface unconsolidated reservoirs, but the optimized NMR-K transform coefficients can be up to two orders of magnitude different from those used in oilfield NMR logging.
David Walsh, Ph.D.
Vista Clara Inc., Mukilteo, WA
David Walsh is the founder and President of Vista Clara. He is in his 16th year managing this small business in the field of geophysical research and development and instrument manufacturing. His most significant contributions have been in the development and commercialization of: multi-channel surface NMR instrumentation for groundwater investigations, small diameter low-cost borehole and direct-push NMR instruments for hydrological investigations, non-invasive NMR-based soil moisture sensors for geotechnical and agricultural investigations, and nuclear quadrupole resonance-based explosive detection systems.
James J. Butler, Ph.D.
Kansas Geological Survey, University of Kansas, Lawrence, KS
Jim Butler is a Senior Scientist and Chief of the Geohydrology Section of the Kansas Geological Survey at the University of Kansas. He holds a B.S. in Geology from the College of William and Mary, and an M.S. and Ph.D. in Applied Hydrogeology from Stanford University. His current research interests include high-resolution subsurface characterization, well responses to natural stimuli, and the role of phreatophytes in stream-aquifer systems.
Gaisheng Liu, Ph D.
University of Kansas, Kansas Geological Survey, Lawrence, KS
Gaisheng Liu is an Assistant Scientist in the Geohydrology Section of the Kansas Geological Survey at the University of Kansas. He holds a B.S. in Hydrogeology and Engineering Geology from Chengdu University of Technology, China, and a Ph.D. in Geology from the University of Alabama. His current research interests focus on development of new methods for improved site characterizations, groundwater resources availability and sustainability modeling, and aquifer storage and recovery in near-surface aquifers.
Steve Knobbe
Kansas Geological Survey, University of Kansas, Lawrence, KS
Steve Knobbe earned a B.S. and M.S. in Geological Engineering from the University of Missouri-Rolla. His current research interests include developing new direct-push tools and methods for high-resolution subsurface characterization.
Edward C. Reboulet
Kansas Geological Survey, University of Kansas, Lawrence, KS
Ed Reboulet is a Senior Research Assistant in the Geohydrology Section of the Kansas Geological Survey at the University of Kansas. He holds a B.S. in Geology from Wright State University and a M.S. in Geology from Boise State University. His current research interests include development of field methods for applied hydrogeology and new applications of direct-push technology for subsurface characterization.
Rosemary Knight
Stanford University, Stanford, CA
Andy Parsekian
Stanford University, Stanford, CA
Andrew Parsekian is an Assistant Professor in the Department of Geology and Geophysics at the University of Wyoming. He holds a B.S. in Environmental Science from Dickinson College and a Ph.D. in Environmental Science from Rutgers University. His research interests include geophysical investigations of groundwater systems and hydrogeophysical measurements of permafrost.
Mercer Barrows
Vista Clara Inc., Mukilteo, WA
Mercer Barrows was previously Staff Geophysicist at Vista Clara. He earned a B.S. in geophysics from the University of California, Santa Barbara. He is currently a geologist at Kleinfelder in Los Angeles, California.