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TitleHydraulic conductivity from nuclear magnetic resonance logs in sediments with elevated magnetic susceptibilities
AuthorCrow, HORCID logo; Paradis, DORCID logo; Grunewald, E; Liang, X X; Russell, H A JORCID logo
SourceGroundwater 2021 p. 1-16,
Alt SeriesNatural Resources Canada, Contribution Series 20210240
PublisherNational Ground Water Association / Wiley
Mediapaper; on-line; digital
File formatpdf; html
Lat/Long WENS -75.3192 -75.2931 45.3108 45.2722
Lat/Long WENS -75.2931 -75.2931 45.3108 45.2722
Subjectssurficial geology/geomorphology; hydrogeology; geophysics; Science and Technology; Nature and Environment; glacial landforms; glacial deposits; eskers; groundwater resources; aquifers; groundwater flow; hydraulic conductivity; wells; geophysical logging; magnetic susceptibility; grain size distribution; porosity; glacial history; deglaciation; Vars-Winchester Esker; Champlain Sea Basin; Laurentide Ice Sheet; glaciofluvial sediments; esker sediments; Methodology; Phanerozoic; Cenozoic; Quaternary
Illustrationstables; location maps; seismic reflection profiles; lithologic logs; geophysical logs; profiles; bar graphs; plots
ProgramGroundwater Geoscience Archetypal Aquifers of Canada
Released2021 12 14
AbstractThis study examined the application of slim-hole nuclear magnetic resonance (NMR) tools to estimate hydraulic conductivity (KNMR) in an unconsolidated aquifer that contains a range of grain sizes (silt to gravel) and high and variable magnetic susceptibilities (MS) (0.0001 to 0.01 SI). A K calibration dataset was acquired at 1-m intervals in three fully screened wells, and compared to KNMR estimates using the Schlumberger-Doll research (SDR) equation with published empirical constants developed from previous studies in unconsolidated sediments. While KNMR using published constants was within an order of magnitude of K, the agreement, overprediction, or underprediction of KNMR varied with the MS distribution in each well. An examination of the effects of MS on NMR data and site-specific empirical constants indicated that the exponent on T2ML (n-value in the SDR equation, representing the diffusion regime) was found to have the greatest influence on KNMR estimation accuracy, while NMR porosity did not improve the prediction of K. KNMR was further improved by integrating an MS log into the NMR analyses. A first approach detrended T2ML for the effects of MS prior to calculating KNMR, and a second approach introduced an MS term into the SDR equation. Both were found to produce similar refinements of KNMR in intervals of elevated MS. This study found that low frequency NMR logging with short echo times shows promise for sites with moderate to elevated MS levels, and recommends a workflow that examines parameter relationships and integrates MS logs into the estimation of KNMR.
Summary(Plain Language Summary, not published)
In traditional groundwater investigations, hydraulic testing methods are used in boreholes to estimate the hydraulic conductivity (K) and porosity of the geological materials, but these methods can be very time consuming in complex settings. The recent adaptation of well-established oil industry borehole nuclear magnetic resonance (NMR) logging tools into small-diameter probes is allowing for rapid and continuous measurement of K and porosity in near-surface groundwater studies. These tools are generating increasing interest in the groundwater field, but a key consideration is their sensitivity to magnetic minerals. This first-of-its kind study in Canada examines the use of NMR logs to predict K in a glacial sediment aquifer with high magnetic susceptibilities in three GSC boreholes near Ottawa Ontario. The study (1) demonstrates close agreement between KNMR and traditional K measurements, (2) proposes a work flow to improve KNMR estimation in settings with elevated magnetic susceptibilities, and (3) concludes that NMR logs could provide considerable benefits to hydrogeologic studies investigating water resource issues in glacial aquifers throughout Canada.

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