The identification of risks associated with the geological storage of CO2 requires methods that can analyse and assess potential safety hazards. This paper evaluates how performance assessment can be used as a method for assessing the impact of CO2 storage on health, safety and the environment (HSE) with particular respect to potential future aquifer storage in the anticlinal structure Schweinrich in Germany. The performance assessment was conducted under the CO2STORE European Fifth Framework project as one of the four cases on the aquifer storage of CO2. It is known as the Schwarze Pumpe case study. Being a case study, it is restrictive from a feasibility study point of view—i.e., the extended identification of the key safety factors where an actual CO2 storage project would be considered for the Schweinrich structure. The study is based on data currently available, gathered in prior surveys, and on the use of simplified models, with CO2 leakage levels from natural analogues being the evaluation criteria. While the results should be interpreted as provisional, they point out clearly which additional data should be gathered in relation to the long-term storage performance in the event that the site warrants further investigation.