An assessment of near surface CO2 leakage detection techniques under Australian conditions  

Authors / CoAuthors

Feitz, A.J. | Jenkins, C.J. | Schacht, U. | McGrath, A. | Berko, H. | Schroder, I.F. | Curnow, S | Zegelin, S. | Sirault, X. | Jimeneze-Berni, J. | George, S.C. | Heath, C.J.

Abstract

Geoscience Australia and the CO2CRC operate a greenhouse gas controlled release facility at an experimental agricultural station maintained by CSIRO Plant Industry in Canberra, Australia. The facility is designed to simulate surface emissions of CO2 (and other greenhouse gases) from the soil into the atmosphere. Over 10 different near surface monitoring techniques were trialled at the Ginninderra controlled release site during 2012-2013. Different climatic conditions for the early 2012 release experiment (wet) and late 2013 release experiment (dry) resulted in markedly different sub-surface plume behaviour and surface expression of CO2. Gaseous CO2 was released 2 m below the ground surface from a slotted, 100 m long horizontal well at a rate of 144 kg/d for at least 8 weeks for both experiments. The most obvious difference between the two release experiments was that CO2 leakage expressed at different locations along the well for the two experiments. As also observed in other controlled release experiments internationally, the surface expression of CO2 during these experiments, as measured using a portable soil flux meter, was restricted to localised spots. For the 2012 (wet) release experiment, the leakage was limited to a small intense primary leak (approximately 12 m in diameter) and a neighbouring small secondary leak. In contrast, the leak from the 2013 (dry) release experiment was broader, spread over a longer length of the release well, and did not attain the very high flux intensities observed in the previous year. An array of 1 m deep soil gas wells provided insight into the migration pathways of CO2 in the sub-surface, showing a much broader dispersion of CO2 in the sub-surface compared to the surface CO2 expression. Krypton tracers confirmed that the spread of the introduced gases in the sub-surface was much greater than the surface expression, with different behaviour observed between the 2012 and 2013 experiments. The differences between the years are attributed to changes in groundwater levels, drier conditions, and a larger vadose zone during the 2013 experiment. Eddy covariance (EC) towers were deployed at the site for both experiments with the objective to detect and quantify CO2 emissions. CO2 leaks were detected above the background and the direction of the leak confirmed. However, analysis showed that current methods of EC are not appropriate for quantifying the CO2 leak, as much of the CO2 flux is lost through advection and diffusion below the measurement height. This is because the footprint of the leak is much smaller than the EC tower's footprint, resulting in a highly heterogeneous system that breaches EC's key assumptions. The results suggest that quantification using EC may not be possible for CO2 leaks with small footprints. An array of atmospheric CO2 sensors was also deployed at the site during the experiments. Application of atmospheric tomographic techniques using the point source sensors appears to be a more effective approach than EC for quantifying CO2 emissions. Broad scale leak detection technologies are necessary for surveying areas beyond high risk sites and is the subject of ongoing research at Ginninderra. Airborne hyperspectral and thermal scanning measurements were taken over CO2-impacted, mature wheat and field pea crops. The CO2 impact on plants was characterised through biochemical analysis and observed changes in plant morphology. High resolution ground-based hyperspectral and thermal measurements were taken over tillering barley and wheat, as well as field pea and canola seedlings. Dry conditions and crop stage strongly influenced the effectiveness of the remote sensing techniques for CO2 leak detection. A comparison between the high resolution ground-based and airborne hyperspectral measurements for detecting CO2 impacted plants will be presented as well as an overall assessment of the leak detection techniques. Submitted to the GHGT-12

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nonGeographicDataset

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78797

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• External PublicationArticle

• AU-ACT

Australian and New Zealand Standard Research Classification (ANZSRC)

• Carbon Sequestration Science

• Published_Internal

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2014-01-01T00:00:00

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Australian Government Security ClassificationSystem    

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asNeeded

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environment

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Data developed under joint GA-CO2CRC collaborative project

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[-35.5, -35.0, 149.0, 149.5]

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12th International Conference on Greenhouse Gas Control Technologies (GHGT-12), 2014, Austin, Texas