Potential Impacts on Groundwater associated with Geological CO2 Storage

Geological CO2 storage bears potential impacts on groundwater. Potable groundwater resources are legally protected, therefore any potential negative impact caused by CO2 storage has to be considered. Injection of CO2 in a deep saline aquifer will alter the physical and chemical conditions in the reservoir. As a consequence, the in situ fluid is compressed, displaced, and migrates away from the injection site. Furthermore, numerous complexly coupled geochemical reactions occur, e.g. dissolution of alumosilicates. The assessment of site-specific and time-dependent coupled physico-chemical processes is vital to evaluate storage security.

Shallow freshwater aquifers can only be affected by the storage of CO2 in deep saline formations if leakage pathways like faults or abandoned wells facilitate the ascent of CO2 or saline formation water. Leakage cannot be excluded, but potential impacts on the environment should be minimized by site-specific monitoring. Groundwater monitoring involves detecting deviations from baseline or expected conditions and investigating causes of anomalies and verification of leakage. A large number of methods and tools are available from classical quantitative and qualitative groundwater monitoring. In practice, groundwater monitoring faces several challenges however. The primary requirements for safe CO2 storage and groundwater protection are thorough site characterization, conservative risk assessments, and unconditional site selection.