A Natural Analogue Approach for Discriminating Leaks of CO2 Stored Underground Using Groundwater Geochemistry Statistical Methods, South Korea

Abstract

Carbon capture and storage (CCS) is one of several useful strategies for capturing greenhouse gases to counter global climate change. In CCS, greenhouse gases such as CO2 that are emitted from stacks are isolated in underground geological storage. Natural analogue studies that can provide insights into possible geological CO2 storage sites, can deliver crucial information about the safety and security of geological sequestration, the long-term impact of CO2 storage on the environment, and the field operation and monitoring requirements for geological sequestration. This study adopted a probability density function (PDF) approach for CO2 leakage monitoring by characterizing naturally occurring CO2-rich groundwater as an analogue that can occur around a CO2 storage site due to CO2 dissolving into fresh groundwater. Two quantitative indices, (QI(tail) and QI(shift)), were estimated from the PDF test and were used to compare CO2-rich and ordinary groundwaters. Key geochemical parameters (pH, electrical conductance, total dissolved solids, HCO3-, Ca2+, Mg2+, and SiO2) in different geological regions of South Korea were determined through a comparison of quantitative indices and the respective distribution patterns of the CO2-rich and ordinary groundwaters.