Application of natural and artificial tracers to constrain CO2 leakage and degassing in the K-COSEM site, South Korea

Abstract

Although Carbon Capture and Storage (CCS) has been demonstrated successfully on many occasions, the po-tentialleakage ofdeepsequestratedCO2intoshallowgroundwaterremainsaconcern.Toaddressthis,anar-tificialinjectionexperimentwasperformedattheK-COSEMtestsiteinEumseong,SouthKorea,thatinvolvedthe release of CO2？infused water (16.9kg of CO2in 5m3) containing He and Kr tracers into a shallow, het-erogeneous, weathered-granite aquifer. The initial CO2？fluid was slightly oversaturated at the subsurface in-jectionpoint,andthustheplumewasexpectedtoinitiallydegasCO2beforeequilibratingatin-situconditions.Monitoring of carbonate system parameters in nearby observation wells helped define the evolution of theinjectedfluids,whilethenoblegastracerswereusedtoclearlydefinethephysicalbehavioroftheCO2plume(includinganestimateofdegassedCO2equalto0.9？3.1%).ThisstudydemonstratesthepotentialuseofnoblegasesformonitoringCO2leakageinshallowaquifers,constrainingmassbalanceandphasechangesofleakingfluids, and better understanding local flow pathways. Furthermore, breakthrough of noble gases in this studywas different from some previous experiments, suggestingthat monitoring efficiencyof these tracers may de-pendonleakageandsiteconditions.