Monitoring of a Simulated CO2 Leakage in a Shallow Aquifer Using Stable Carbon Isotopes

Artificial carbon dioxide leakage into a shallow aquifer was monitored using stable carbon isotope measurements at a field site near the town of Wittstock, Brandenburg, Germany. Approximately 400 000 L of CO2 were injected into a shallow aquifer at 18 m depth over 10 days. The 13C/ 12C ratios of the CO2 were measured in both groundwater and soil gas samples to monitor the distribution of the injected CO2 plume and to evaluate the feasibility and reliability of this approach to detect potential CO2 leakage, for example from carbon capture and storage (CCS) sites. The isotopic composition of the injected CO213C −30.5 ‰) was differentiable from the background CO213C −21.9 ‰) and the artificial CO2 plume was monitored over a period spanning more than 204 days. The results demonstrate that this stable isotope monitoring approach can be used to identify CO2 sources and detect potential CO2 migration from CCS sites into overlying shallow aquifers or even into the upper subsurface. A significant difference between the isotope ratios of the natural background and the injected CO2 is required for this monitoring approach to be effective.