Scholarly Work - Civil Engineering

Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/3460

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Bulk electric conductivity response to soil and rock CO2 concentration during controlled CO2 release experiments: Observations & analytic modeling
(2015-09) Jewell, Scott; Zhou, Xiaobing; Apple, Martha E.; Dobeck, Laura M.; Spangler, Lee H.; Cunningham, Alfred B.
To develop monitoring technologies for geologic CO2 storage, controlled CO2 release experiments at the Zero Emissions Research and Technology (ZERT) site in Bozeman, Montana, USA, were carried out in 2009-2011. To understand the impact on the electric properties of soil and sediment rock due to possible CO2 leakage, we have developed an analytical model to explain and predict the electric conductivity (EC) for CO2 impacted soil and sedimentary rock. Results from the model were compared with the measurements at the ZERT site during 2009â€“2011 and the CO2-Vadose Project site in France in 2011-2012 after model calibration at each site. The model was calibrated using the saturation (n) and cementation (m) exponents contained in Archie's equation, and a chemistry coefficient (pKc) as tuning parameters that minimized the misfit between observed and modeled soil/rock bulk conductivity data. The calibration resulted in n=3.15, m=2.95, and pKc=4.7 for the ZERT site, which was within the range of values in the literature. All the ZERT data sets had rms errors of 0.0115-0.0724. For the CO2-Vadose site, calibration resulted in n=3.6-9.85 and m=2.5-4.2, pKc=4.80-5.65, and the rms error of 0.0002-0.0003; the cementation exponents were consistent with the literature. These results found that the model predicted the bulk EC reasonably well in soil and rock once the unmeasurable model parameters (n, m, and pKc) were calibrated.
Using hyperspectral plant signatures for CO2 leak detection during the 2008 ZERT CO2 sequestration field experiment in Bozeman, MT
(2010-03) Male, Erin J.; Pickles, William L.; Silver, Eli A.; Hoffmann, Gary D.; Lewicki, Jennifer; Apple, Martha E.; Repasky, Kevin S.; Burton, Elizabeth A.
Hyperspectral plant signatures can be used as a short-term, as well as long-term (100-year timescale) monitoring technique to verify that CO2 sequestration fields have not been compromised. An influx of CO2 gas into the soil can stress vegetation, which causes changes in the visible to near-infrared reflectance spectral signature of the vegetation. For 29 days, beginning on July 9, 2008, pure carbon dioxide gas was released through a 100-m long horizontal injection well, at a flow rate of 300 kg day−1. Spectral signatures were recorded almost daily from an unmown patch of plants over the injection with a “FieldSpec Pro” spectrometer by Analytical Spectral Devices, Inc. Measurements were taken both inside and outside of the CO2 leak zone to normalize observations for other environmental factors affecting the plants. Four to five days after the injection began, stress was observed in the spectral signatures of plants within 1 m of the well. After approximately 10 days, moderate to high amounts of stress were measured out to 2.5 m from the well. This spatial distribution corresponded to areas of high CO2 flux from the injection. Airborne hyperspectral imagery, acquired by Resonon, Inc. of Bozeman, MT using their hyperspectral camera, also showed the same pattern of plant stress. Spectral signatures of the plants were also compared to the CO2 concentrations in the soil, which indicated that the lower limit of soil CO2 needed to stress vegetation is between 4 and 8% by volume.