| Title | Evaluation of slim-hole NMR logging for hydrogeologic insights into dolostone and sandstone aquifers |
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| Author | Pehme, P ; Crow,
H; Parker, B; Russell, H |
| Source | Journal of Hydrology vol. 610, 127809, 2022 p. 1-18, https://doi.org/10.1016/j.jhydrol.2022.127809  Open Access |
| Image |  |
| Year | 2022 |
| Alt Series | Natural Resources Canada, Contribution Series 20210226 |
| Publisher | Elsevier |
| Document | serial |
| Lang. | English |
| Media | paper; digital; on-line |
| File format | pdf; html |
| Province | Ontario |
| NTS | 31G/05; 40P/09 |
| Area | Ottawa; Guelph |
| Lat/Long WENS | -76.0000 -75.5000 45.5000 45.2500 |
| Lat/Long WENS | -80.5000 -80.0000 43.7500 43.5000 |
| Subjects | hydrogeology; sedimentology; geophysics; Science and Technology; Nature and Environment; groundwater resources; aquifers; hydrostratigraphic units; geophysical logging; boreholes; bedrock geology;
lithology; sedimentary rocks; dolostones; sandstones; clays; porosity; equipment testing |
| Illustrations | location maps; geoscientific sketch maps; stratigraphic columns; plots; schematic diagrams; tables; geophysical logs; profiles; photographs; geophysical images |
| Program | Groundwater Geoscience Archetypal Aquifers of Canada |
| Released | 2022 05 14 |
| Abstract | This study assesses the performance and limitations of slim-hole borehole nuclear magnetic resonance (NMR) technology from a hydrogeologic perspective in fractured, porous rock. NMR logging was carried
out in dolomitic and sandstone bedrock boreholes at two research test sites in Ontario, Canada, where aquifer and aquitard units provide a range of clay contents as well as a variety of primary and secondary porosity types (e.g. discrete fractures,
reefal structures, vugs and karstic conduits). Results were compared to core measurements, geophysical logs, and hydrogeophysical testing. The vertical response curve of the instrument tested was found to produce 60% of the signal from within a 0.2m
span surrounding the measuring point. The repeatability of the total porosity measurements in stationary mode is excellent where the porosity is greater than 0.15. Below that threshold, repeatability is scattered at ±0.05 porosity about the mean,
with the variability primarily within the clay- and capillary-bound fractions. The NMR porosity estimates agreed with core measurements to within ±0.04 porosity in both the dolostone and sandstone, but the correlation deteriorates in finely bedded
lithologies, and where fracturing is present. Much of the discrepancy is attributed to scaling in a finely layered geologic sequence, as the core samples are much smaller than the entire volume measured with NMR probes. Data collection with the probe
in motion (continuous logging) added variability to the response when compared to stationary recordings. Although broadscale trends were comparable, the details and depth-specific insights of the bound fluid fractions varied with logging rates.
Overall, NMR provides a robust measurement of the bulk matrix porosity and pore size distribution of lithologies intersected, both of which are critically important parameters in understanding hydrogeologic conditions and contaminant distributions in
layered sedimentary rock systems. |
| Summary | (Plain Language Summary, not published)
Over the past ten years, a new geophysical logging tool has reached the market. It uses the same principles as magnetic resonance imaging (MRI)
technology to scan human tissues, but the logging tool estimates the quantity and mobility of groundwater in rock and sediment in boreholes. This logging technology, called borehole nuclear magnetic resonance (bNMR) is mature in the oil and gas
industry, but has only recently been scaled down to fit inside the narrow diameter boreholes drilled for environmental studies. This makes the new technology particularly powerful for groundwater investigations, as no other borehole tools can assess
the range of parameters (water content, pore size distribution, and permeability) reported by the manufacturers. This study assesses the performance and limitations of slim-hole (bNMR) technology from a hydrogeologic perspective in the fractured,
porous rock of southern Ontario. NMR logging was carried out in sedimentary bedrock boreholes at two research test sites operated by the Geological Survey of Canada (Ottawa) and the University of Guelph (Guelph). Results were compared to an extensive
dataset of core measurements, geophysical logs, and hydro-geophysical testing. The tool was found to provide a robust measurement of rock porosity and pore size distribution throughout the six boreholes tested, parameters that are critically
important in understanding hydrogeologic conditions and contaminant distributions in layered sedimentary rock systems. |
| GEOSCAN ID | 328835 |
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