A leak monitoring method for CO2 storage sites using ratio of ΔCO2:ΔO2 at the soil surface

Carbon Capture and Storage (CCS) technology has a high potential for reducing carbon emission at large scales. However, the success of CCS projects vastly depends on the continuous monitoring of injected CO2 and ensuring it remains below ground. The technology currently available for monitoring sites are mainly adopted from disciplines which are effective at detecting high volume leaks but may not be reliable in distinguishing seepage of CO2 from underground and fossil fuel combustion at the surface. We have constructed a numerical model that includes soil characteristics and the bio-geo-chemical dynamics of near surface soils and soil gases. The simulation of our model can predict O2 and CO2 profiles in soil and differential ratios with respect to atmospheric concentrations (ΔCO2 and ΔO2), and distinguish CO2 leaks. Experiments on a 1-m soil column have been conducted using dual channel IR and fuel cell analyzers to verify our model predictions. The preliminary results show that measured O2 and CO2 concentrations in near-surface soil layers and the ratio of ΔCO2:ΔO2 at the soil surface are in agreement with our model. Based on initial results it is expected that this method of monitoring will able to detect fluxes as small as 2-6µmole/m2/s of CO 2 leakage.