Tracing the movement and the fate of injected CO2 at the IEA GHG Weyburn-Midale CO2 Monitoring and Storage project (Saskatchewan, Canada) using carbon isotope ratios

Stable isotope data can assist in successful monitoring of the movement and the fate of injected CO2 in enhanced oil recovery and geological storage projects. This is demonstrated for the International Energy Agency Greenhouse Gas (IEA-GHG) Weyburn-Midale CO2 Monitoring and Storage Project (Saskatchewan) where fluid and gas samples from multiple wells were collected and analyzed for geochemical and isotopic compositions for more than a decade. Carbon isotope ratios of the injected CO2 (−20.4‰) were sufficiently distinct from median δ13C values of background CO2 (δ13C = −12.7‰) and HCO3− (δ13C = −1.8‰) in the reservoir to reveal the movement and geochemical trapping of injected CO2 in the reservoir. The presented 10-year data record reveals the movement of injected CO2 from injectors to producers, dissolution of CO2 in the reservoir brines, and ionic trapping of injected CO2 in conjunction with dissolution of carbonate minerals. We conclude that carbon isotope ratios constitute an excellent and cost effective tool for tracing the fate of injected CO2 at long-term CO2 storage sites with injection rates exceeding 1 million tons per year.