Présentations Colloques

K-COSEM (Korea-CO2 Storage Environmental Monitoring) site is a field experimental site intended for studying shallow-depth subsurface and surface environmental impacts caused by artificially injected CO2. Main objectives of this study is to construct and operate efficient groundwater monitoring network appropriate for hydrogeological characteristics in field-scale transport of CO2 originated from artificially injected CO2 at the K-COSEM site in Eumseong, South Korea. Various hydraulic tests were performed to identify the hydraulic characteristics such as hydraulic conductivity, effective porosity, and groundwater flow direction. Hydraulic tests and electromagnetic flow meter tests were conducted to estimate groundwater flow direction by well to well scale, which was compared with regional groundwater flow direction and velocity estimated from hydraulic head distribution. This comparison indicated local variations in flow direction and velocity exist that could generate variations in CO2 monitoring results. Push-and-pull tracer tests using chloride and SF6 were conducted at different depth intervals of the shallow-depth aquifer in the K-COSEM site. By analyzing the breakthrough curves and the mass recovery percentage of tracers, the groundwater velocity and effective porosity were computed. Recovery ratios of tracers were estimated as 90~96 % for chloride while much lower 47 % for SF6. The exact reason of the difference in recovery ratios was not clarified yet, but it indicated that, for a volatile tracer, not only dissolved phase in groundwater but gaseous phase in groundwater and vadose zone should be examined for a complete mass balance analysis. Based on this idea, multi-level groundwater monitoring wells linked to multi-level soil gas monitoring facilities were installed at the K-COSEM site. Before CO2 injection to shallow aquifer, preliminary tracer tests were performed by using aqueous and volatile tracers.