Design and and Construction of Groundwater Monitoring Network at Shallow-depth CO2 Injection and Leak Test Site, Korea

Abstract

The effectiveness of CO2 leakage characterization is highly dependent on reasonable monitoring network designs for detecting the CO2 leakage under various hydrogeological conditions. Also, the migration of CO2 through heterogeneous subsurface is very difficult to predict because small differences in material properties may result in vastly different migration patterns. Therefore, like other environmental contaminants, it is necessary to design optimized groundwater monitoring network to effectively characterize the migration of the CO2. Main objectives of this study is to construct optimized groundwater monitoring network considering hydrogeological characteristics in field-scale transport of CO2 originated from artificially-injected CO2 at the environmental impact monitoring test site in Eumseong, Korea (K-COSEM). 24 monitoring wells were installed at the site aligned with the regional groundwater flow direction. Various hydraulic tests were performed to estimate the hydraulic characteristics such as hydraulic conductivity, effective porosity, and groundwater velocity. Groundwater monitoring network for CO2 injection and leak test constructed with regard of the heterogeneity understood through the various field tests. Three multi-depth monitoring well nests each of them was composed of four monitoring well units drilled with different depths (each 18, 22, 26, 30 m deep) have been installed along the groundwater flow direction and dedicated to depth-discrete water quality monitoring in saturated zone. Additional, four multi-depth monitoring well nests each of them was composed of four unsaturated-zone monitoring well units drilled with different depths (each 5, 8, 11, 14 m deep) were also installed with a distance of 1.25 m away between saturated zone monitoring wells and were dedicated to depth-discrete gas monitoring in unsaturated zone. By these efforts, effective groundwater monitoring network for temporal and spatial CO2 leakage detection and groundwater safety management have been designed and constructed at the test site.