| Title | Hydraulic conductivity from nuclear magnetic resonance logs in sediments with elevated magnetic susceptibilities |
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| Author | Crow, H ; Paradis,
D; Grunewald, E; Liang, X X; Russell, H A J |
| Source | Groundwater 2021 p. 1-16, https://doi.org/10.1111/gwat.13158 |
| Image |  |
| Year | 2021 |
| Alt Series | Natural Resources Canada, Contribution Series 20210240 |
| Publisher | National Ground Water Association / Wiley |
| Document | serial |
| Lang. | English |
| Media | paper; on-line; digital |
| File format | pdf; html |
| Province | Ontario |
| NTS | 31G/06 |
| Area | Embrun |
| Lat/Long WENS | -75.3192 -75.2931 45.3108 45.2722 |
| Lat/Long WENS | -75.2931 -75.2931 45.3108 45.2722 |
| Subjects | surficial 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 |
| Illustrations | tables; location maps; seismic reflection profiles; lithologic logs; geophysical logs; profiles; bar graphs; plots |
| Program | Groundwater Geoscience Archetypal Aquifers of Canada |
| Released | 2021 12 14 |
| Abstract | This 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. |
| GEOSCAN ID | 328846 |
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