In this study, we examined the groundwater monitoring data from the national groundwater monitoring station in Andong at the southeastern part of South Korea. The monitoring station is located in Cretaceous Gyeongsang sedimentary basin which has been considered for geologic CO2 storage in South Korea. Groundwater at the station is characteristically CO2-rich and typically shows a vertical stratification of water chemistry with depth. Groundwater at shallow depths (< 7 m deep) has low electrical conductivity (EC) values, ca. 280 μS/cm, while deeper groundwater (down to 70 m below the land surface) has higher EC values (up to 3,900 μS/cm). The EC logging in the well also shows the significant stepwise variation of the EC values with depth. The results of the well logging of physicochemical data in conjunction with the borehole imaging using a nano camera and the hydrochemical analysis of groundwater indicate that the observed vertical stratification in the well is the result of physicochemical changes of CO2-rich groundwater with high EC values via CO2 outgassing and associated precipitation of minerals during ascending. The results of the present study demonstrate that, provided there is vertical stratification of EC in a monitoring well or in a storage site, geochemical monitoring at shallow depths may lead to a bias in the monitoring results. Our results suggest the following implications: 1) careful baseline data analysis at several depths is required for precise groundwater monitoring in CO2 storage sites and 2) based on the good understanding of hydrogeological condition, proper sites and depths of geochemical monitoring should be selected.
|Number of pages||7|
|Publication status||Published - 2017|
|Event||13th International Conference on Greenhouse Gas Control Technologies, GHGT 2016 - Lausanne, Switzerland|
Duration: 2016 Nov 14 → 2016 Nov 18
Bibliographical notePublisher Copyright:
© 2017 The Authors.
- CO-rich water
- electric conductivity
- geologic carbon storage
- groundwater monitoring
- vertical stratification
ASJC Scopus subject areas