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| Titel |
Detection of CO2 leakage by the surface-soil CO2-concentration monitoring (SCM) system in a small scale CO2 release test |
| VerfasserIn |
Gitak Chae, Soonyoung Yu, Ki-Sung Sung, Byoung-Young Choi, Jinyoung Park, Raehee Han, Jeong-Chan Kim, Kwon Gyu Park |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250104805
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| Publikation (Nr.) |
 EGU/EGU2015-4243.pdf |
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| Zusammenfassung |
| Monitoring of CO2 release through the ground surface is essential to testify the safety of CO2
storage projects. We conducted a feasibility study of the multi-channel surface-soil
CO2-concentration monitoring (SCM) system as a soil CO2 monitoring tool with a small
scale injection. In the system, chambers are attached onto the ground surface, and
NDIR sensors installed in each chamber detect CO2 in soil gas released through the
soil surface. Before injection, the background CO2 concentrations were measured.
They showed the distinct diurnal variation, and were positively related with relative
humidity, but negatively with temperature. The negative relation of CO2 measurements
with temperature and the low CO2 concentrations during the day imply that CO2
depends on respiration. The daily variation of CO2 concentrations was damped with
precipitation, which can be explained by dissolution of CO2 and gas release out
of pores through the ground surface with recharge. For the injection test, 4.2 kg
of CO2 was injected 1 m below the ground for about 30 minutes. In result, CO2
concentrations increased in all five chambers, which were located less than 2.5 m of distance
from an injection point. The Chamber 1, which is closest to the injection point,
showed the largest increase of CO2 concentrations; while Chamber 2, 3, and 4
showed the peak which is 2 times higher than the average of background CO2.
The CO2 concentrations increased back after decreasing from the peak around 4
hours after the injection ended in Chamber 2, 4, and 5, which indicated that CO2
concentrations seem to be recovered to the background around 4 hours after the
injection ended. To determine the leakage, the data in Chamber 2 and 5, which had low
increase rates in the CO2 injection test, were used for statistical analysis. The result
shows that the coefficient of variation (CV) of CO2 measurements for 30 minutes is
efficient to determine a leakage signal, with reflecting the abnormal change in CO2
concentrations. The CV of CO2 measurements for 30 minutes exceeded 5% about 5 minutes
before the maximum CO2 concentration was detected. The contributions of this
work are as follows: (1) SCM is an efficient monitoring tool to detect the CO2
release through the ground surface. (2) The statistical analysis method to determine
the leakage and a monitoring frequency are provided, with analyzing background
concentrations and CO2 increases in a small-scale injection test. (3) The 5% CV of CO2
measurements for 30 minutes can be used for the early warning in CO2 storage sites. |
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