Browsing by Author "Dobeck, Laura M."

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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.
Eddy covariance observations of surface leakage during shallow subsurface CO2 releases
(2009-06) Lewicki, Jennifer L.; Hilley, George E.; Fischer, Marc L.; Pan, Lehua; Oldenburg, Curtis M.; Dobeck, Laura M.; Spangler, Lee H.
We tested the ability of eddy covariance (EC) to detect, locate, and quantify surface CO2 flux leakage signals within a background ecosystem. For 10 days starting on 9 July 2007, and for 7 days starting on 3 August 2007, 0.1 (Release 1) and 0.3 (Release 2) t CO2 d−1, respectively, were released from a horizontal well ∼100 m in length and ∼2.5 m in depth located in an agricultural field in Bozeman, Montana. An EC station measured net CO2 flux (Fc) from 8 June 2006 to 4 September 2006 (mean and standard deviation = −12.4 and 28.1 g m−2 d−1, respectively) and from 28 May 2007 to 4 September 2007 (mean and standard deviation = −12.0 and 28.1 g m−2 d−1, respectively). The Release 2 leakage signal was visible in the Fc time series, whereas the Release 1 signal was difficult to detect within variability of ecosystem fluxes. To improve detection ability, we calculated residual fluxes (Fcr) by subtracting fluxes corresponding to a model for net ecosystem exchange from Fc. Fcr had reduced variability and lacked the negative bias seen in corresponding Fc distributions. Plotting the upper 90th percentile Fcr versus time enhanced the Release 2 leakage signal. However, values measured during Release 1 fell within the variability assumed to be related to unmodeled natural processes. Fcr measurements and corresponding footprint functions were inverted using a least squares approach to infer the spatial distribution of surface CO2 fluxes during Release 2. When combined with flux source area evaluation, inversion results roughly located the CO2 leak, while resolution was insufficient to quantify leakage rate.
Experimental observation of signature changes in bulk soil electrical conductivity in response to engineered surface CO2 leakage
(2012-03) Zhou, Xiaobing; Lakkaraju, V. R.; Apple, Martha E.; Dobeck, Laura M.; Gullickson, K.; Shaw, Joseph A.; Cunningham, Alfred B.; Wielopolski, Lucian; Spangler, Lee H.
Experimental observations of signature changes of bulk soil electrical conductivity (EC) due to CO2 leakage were carried out at a field site at Bozeman, Montana, to investigate the change of soil geophysical properties in response to possible leakage of geologically sequestered CO2. The dynamic evolution of bulk soil EC was measured during an engineered surface leakage of CO2 through in situ continuous monitoring of bulk soil EC, soil moisture, soil temperature, rainfall rate, and soil CO2 concentration to investigate the response of soil bulk EC signature to CO2 leakage. Observations show that: (1) high soil CO2 concentration due to CO2 leakage enhances the dependence of bulk soil EC on soil moisture. The bulk soil EC is a linear multivariate function of soil moisture and soil temperature, the coefficient for soil moisture increased from 2.111 dS for the non-leaking phase to 4.589 dS for the CO2 leaking phase; and the coefficient for temperature increased from 0.003 dS/Â°C for the non-leaking phase to 0.008 dS/Â°C for the CO2 leaking phase. The dependence of bulk soil EC on soil temperature is generally weak, but leaked CO2 enhances the dependence,(2)after the CO2 release, the relationship between soil bulk EC and soil CO2 concentration observes three distinct CO2 decay modes. Rainfall events result in sudden changes of soil moisture and are believed to be the driving forcing for these decay modes, and (3) within each mode, increasing soil CO2 concentration results in higher bulk soil EC. Comparing the first 2 decay modes, it is found that the dependence of soil EC on soil CO2 concentration is weaker for the first decay mode than the second decay mode.
A shallow subsurface controlled release facility in Bozeman, Montana, USA, for testing near surface CO2 detection techniques and transport models
(2010-03) Spangler, Lee H.; Dobeck, Laura M.; Repasky, Kevin S.; Nehrir, Amin R.; Humphries, Seth D.; Barr, Jamie L.; Keith, Charlie J.; Shaw, Joseph A.; Rouse, Joshua H.; Cunningham, Alfred B.; Benson, Sally M.; Oldenburg, Curtis M.; Lewicki, Jennifer L.; Wells, Arthur W.; Diehl, J. Rodney; Strazisar, Brian R.; Fessenden, Julianna E.; Rahn, Thom A.; Amonette, James E.; Barr, Jon L.; Pickles, William L.; Jacobson, James D.; Silver, Eli A.; Male, Erin J.; Rauch, Henry W.; Gullickson, Kadie S.; Trautz, Robert; Kharaka, Yousif; Birkholzer, Jens; Wielopolski, Lucien
A controlled field pilot has been developed in Bozeman, Montana, USA, to study near surface CO2 transport and detection technologies. A slotted horizontal well divided into six zones was installed in the shallow subsurface. The scale and CO2 release rates were chosen to be relevant to developing monitoring strategies for geological carbon storage. The field site was characterized before injection, and CO2 transport and concentrations in saturated soil and the vadose zone were modeled. Controlled releases of CO2 from the horizontal well were performed in the summers of 2007 and 2008, and collaborators from six national labs, three universities, and the U.S. Geological Survey investigated movement of CO2 through the soil, water, plants, and air with a wide range of near surface detection techniques. An overview of these results will be presented.
Surface CO2 leakage during two shallow subsurface CO2 releases
(2007-12) Lewicki, Jennifer L.; Oldenburg, Curtis M.; Dobeck, Laura M.; Spangler, Lee H.
A new field facility was used to study CO2 migration processes and test techniques to detect and quantify potential CO2 leakage from geologic storage sites. For 10 days starting 9 July 2007, and for seven days starting 3 August 2007, 0.1 and 0.3 t CO2 d−1, respectively, were released from a ∼100‐m long, sub‐water table (∼2.5‐m depth) horizontal well. The spatio‐temporal evolution of leakage was mapped through repeated grid measurements of soil CO2 flux (FCO2). The surface leakage onset, approach to steady state, and post‐release decline matched model predictions closely. Modeling suggested that minimal CO2 was taken up by groundwater through dissolution, and CO2 spread out on top of the water table. FCO2 spatial patterns were related to well design and soil physical properties. Estimates of total CO2 discharge along with soil respiration and leakage discharge highlight the influence of background CO2 flux variations on detection of CO2 leakage signals.