Groundwater chemistry and isotope signatures of potential CCS sites in Korea - A baseline study for leakage detection

This research aimed at drawing a baseline of groundwater chemistry and its stable isotope signatures of hydrogen, oxygen and carbon from the deep groundwater above the CO2 sequestration layer, in which physico-chemical conditions are conceived as temperature over 40 degree Celcius and high total dissolved solids. Samples were collected from hot springs (at surface and from seep wells) and high-carbonate springs. Based on water compositions, three groups were identified as saline, alkali-carbonate and soda spring types. Saline type hot springs at the west coastline area contain -14.5‰ δ13C of CO2. Before and after rainfall events, δ13C value of samples shows no change. Hot springs at Suanbo region, located at the center are of the Korean Peninsular, were collected from deep wells of 750 m in depth, and they show the alkali-carbonate type water having δ13C values (-11.3~-10.9‰) and ECs (364~431μS/cm). Both saline and alkali-carbonate type waters show no significant change in composition, indicating that recharge by precipitation has no effect on these groundwater. All the high-carbonate springs were collected at ground surface, and enriched with Ca, Mg and HCO3., probably caused by the dissolution of CO2, and high EC values of 1,016 μS/cm. Soda springs located in Chungcheongbuk-do region have -6.8~-6.7‰ δ13C of CO2, indicating that the source of CO2 could be the upper mantle affected by the carbonate minerals in the Quaternary sedimentary bedrock. On the contrary, carbonate waters in the Gangwon-do region have -3.9~-3.7‰ δ13C of CO2, clearly indicating the source of CO2 being the upper mantle (Gerlach and Taylor, 1990). More detailed chemical and isotopic signatures of the sampled waters will be discussed in presentation.