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TitleDownhole nuclear magnetic resonance logging in glaciomarine sediments near Ottawa, Ontario, Canada
AuthorCrow, HORCID logo; Enkin, RORCID logo; Percival, J BORCID logo; Russell, H A JORCID logo
SourceNear Surface Geophysics 2020 p. 1-117,
Alt SeriesNatural Resources Canada, Contribution Series 20190651
PublisherJohn Wiley and Sons Inc.
Mediapaper; on-line; digital
File formatpdf; html
AreaOttawa; Canada
Lat/Long WENS -76.3828 -75.2394 45.6256 45.1567
SubjectsScience and Technology; hydrogeology; sedimentology; porosity; marine ecology; ecology; boreholes
Illustrationslocation maps; tables; graphs; diagrams; cross-plots
ProgramGroundwater Geoscience Aquifer Assessment & support to mapping
Released2020 07 16
AbstractBorehole nuclear magnetic resonance (NMR) technology was applied in four boreholes intersecting glaciomarine sediments of the Ottawa Valley, Ontario. The study evaluated the ability of slim-hole NMR tools to measure in situ water contents for geohazard and hydrogeological applications. The sediments are composed of clay- and silt-sized grains of glacially eroded rock flour derived from the Precambrian Shield containing trace amounts of magnetic minerals, and porosities ranging from 40 to 74 porosity units (PU, 1% porosity=1 PU). Two Vista Clara Inc. NMR instruments were deployed with echo times of 0.5 ms and 1 ms, and diameters of investigation ranging from 14.0 to 30.5 cm. Quantitative porosities in the sediments were typically within ±5 PU (95% within ±10 PU) of core calibration datasets in the silty clays. This was found to deviate, however, where the grainsize of magnetite particles decreased from silt- and clay-sized to nanoparticles, interpreted to be causing the increased relaxation times which led to underestimation of true water contents. Clay mineralogy and pore water chemistry were also examined as contributing factors, but were not found to significantly shorten NMR relaxation responses. Very short T2 times (<2 ms) are typical in these particular silty-clays, requiring a tool with an echo spacing of <1 ms. Due to the geotechnical sensitivity of the sediments, an NMR instrument with a large diameter of investigation provided needed signal penetration beyond the disturbed zone around the casing.
Summary(Plain Language Summary, not published)
The same technology used for magnetic resonance imaging (MRI) in medical applications is being used to image the amount of groundwater in rocks and sediment. This technology is called borehole magnetic resonance (BMR) imaging in geological settings, and is helping us understand groundwater storage. While BMR has been used in large-diameter oil and gas industry wells since the 1990's, it has only been recently adapted for logging in narrow-diameter water wells and shallow geotechnical boreholes. This makes BMR a valuable new technology to integrate into the group of borehole instruments LMS already uses to study rock, sediment, and groundwater. A study was undertaken to look at a new BMR tool in four LMS research boreholes that were drilled into sediments prone to landsliding. The study concluded that the new BMR tool has many practical applications in landslide and groundwater protection studies - topics of ongoing research in LMS Programs.

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