| Title | Downhole nuclear magnetic resonance logging in glaciomarine sediments near Ottawa, Ontario, Canada |
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| Author | Crow, H ; Enkin,
R; Percival, J B; Russell, H A J |
| Source | Near Surface Geophysics 2020 p. 1-117, https://doi.org/10.1002/nsg.12120 |
| Image |  |
| Year | 2020 |
| Alt Series | Natural Resources Canada, Contribution Series 20190651 |
| Publisher | John Wiley and Sons Inc. |
| Document | serial |
| Lang. | English |
| Media | paper; on-line; digital |
| File format | pdf; html |
| Province | Ontario |
| Area | Ottawa; Canada |
| Lat/Long WENS | -76.3828 -75.2394 45.6256 45.1567 |
| Subjects | Science and Technology; hydrogeology; sedimentology; porosity; marine ecology; ecology; boreholes |
| Illustrations | location maps; tables; graphs; diagrams; cross-plots |
| Program | Groundwater Geoscience Aquifer Assessment & support to mapping |
| Released | 2020 07 16 |
| Abstract | Borehole 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. |
| GEOSCAN ID | 322193 |
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