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.