Characterizing the spatial distribution of CO2 leakage from the shallow CO2 release experiment in South Korea

This study was conducted to detect and characterize potential CO2 leakage from the K-COSEM shallow CO2 release experiment. The study site was established in Eumseong, South Korea, and consisted of five zones divided into two lines (east and west). Approximately 1.8 t CO2 was injected from the perforated release well at Zones 1-4 from June 1-30, 2016. CO2 fluxes varied due to the uneven permeability of soil, and CO2 leakage at the surface was detected within small area (<10 m across). In-soil CO2 concentrations within 5 m from the well were also significantly higher than those measured at 10 m from the well. These results confirmed that the spatial distribution of in-soil CO2 is strongly affected by soil properties and atmospheric pressure effects. Non-linear regression and CO2:O2 ratio analyses were conducted to determine whether there is a CO2 leakage. Even though maximum CO2 concentrations at some leak points were as low as the background concentration, CO2 concentration clearly increased. The CO2:O2 ratios from the CO2 release experiments were completely different from the ratios associated with the biological reaction. Those methods seem to be practical use as indicators of CO2 leakage detection.