A meta-analysis of the surface soil gas measurement monitoring and verification (MMV) program at the Aquistore project

Carbon Capture and Storage (CCS) is playing a greater role in reducing CO2 emissions. The Aquistore project at Estevan, Saskatchewan, Canada is an operational CCS demonstration and research site. Surface soil gas geochemistry is one method of Measurement, Monitoring, and Verification (MMV) techniques used for detection of leakage at CO2 injection sites. We have been operating the surface soil gas MMV program for several years, which has involved measuring gas concentrations of CO2, O-2, N-2, CH4, the stable isotope of CO2 ( delta C-13), and radiocarbon isotope Delta(CO2)-C-14 as tracers for storage containment analysis. Soil CO2 surface flux measurements were also conducted during the baseline monitoring program. At Aquistore, CO2 concentration is typically elevated relative to the mean for the location, but such values are characteristic in this area. Ratio-based tracer analyses, such as O-2 vs. CO2, CO2 vs. N-2, and CO2 vs. N-2/O-2, all indicated that storage is secure. The Delta(CO2)-C-14 values observed in soil gas were interesting in the parts of the site which had a more depleted baseline than expected. To date, there have been no changes in the soil gas indicators since the injections started. These observations will help to inform new research aimed at improving the effectiveness and efficiency of soil gas MMV at Aquistore and similar projects worldwide.