JpGU-AGU Joint Meeting 2020

Presentation information

[J] Oral

H (Human Geosciences ) » H-SC Social Earth Sciences & Civil/Urban System Sciences

[H-SC07] CCUS (Carbon Dioxide Capture, Utilization, and Storage) for Climate Mitigation

convener:Masao Sorai(Institute for Geo-Resources and Environment, National Institute of Advanced Industrial Science and Technology), Ziqiu Xue(Research Institute of Innovative Tech for the Earth), Masaatsu Aichi(Graduate School of Frontier Sciences, University of Tokyo), Yoshihiro Konno(The University of Tokyo)

[HSC07-11] Detection method of anomaly using relative index of spatial variations of DIC for CO2 leakage monitoring on CO2 sub-seabed storage

*Yuji Watanabe1,2, Keisuke Uchimoto1,2, Saeko Mito1,2, Ziqiu Xue1,2 (1.Research Institute of Innovative Technology for the Earth, 2.Geological Carbon Dioxide Storage Technology Research Association)

Keywords:Sub-seabed CO2 storage, Coastal monitoring, CO2 leakage, Dissolved inorganic carbonate

When CO2 is stored in sub-seabed geological formations in Japan, marine monitoring is mandatory to detect CO2 leakage as soon as possible should it occur. In the Tomakomai CCS Demonstration Project, a threshold line based on a negative correlation between partial pressure of CO2 (pCO2) and dissolved Oxygen saturation in seawater is used to detect an anomalously high value of pCO2, which is suspected to be a sign of CO2 leakage. However, these indexes had large fluctuation and caused several pseudo-anomalous errors in the project. Dissolved CO2 in seawater dissociate into H2CO3, HCO3- and CO32-. The proportion of H2CO3 which is correspond to pCO2 is less than 1 % among total dissolved CO2 (DIC) in seawater. If CO2 leak into seawater, pCO2 reflects the leaked CO2 but is affected by various factors; e.g. water temperature, pH, and total alkalinity. However, the amount of leaked CO2 is summed in DIC itself. Accordingly, we try to assess the CO2 leakage using DIC. In this study, we propose the new index using the spatial variations of DIC. This index has suitable for the monitoring not in the injection phase but also in the post-injection period, because the index eliminates the interannual variation including the decadal increases of atmospheric CO2, and also the intra-annual fluctuation resulted from the seasonal change.