CO2 storage potential of the Middle Buntsandstein Subgroup - German sector of the North Sea

•Mapping of CO2 storage sites in the Buntsandstein subgroup in the exclusive economic zone of the German North Sea.•Static CO2 storage capacity estimation via Monte Carlo simulations.•Evaluation of individual storage sites in terms of structural complexity and compartmentalisation. The storage of CO2 in deeply buried geological formations provides a contribution to mitigate hard-to-abate CO2 emissions from industry. Robust geological models and capacity estimations are crucial for the successful planning and implementation of safe storage projects. This study focuses on the CO2 storage potential of the Middle Buntsandstein Subgroup within the Exclusive Economic Zone of the German North Sea. We have mapped a total of 71 potential storage sites based on existing 3D models, seismic and well data. Static CO2 capacities are calculated for each structure using Monte Carlo simulations with 10,000 iterations to account for uncertainties. All potential reservoirs are evaluated based on their potential capacity, burial depth, top seal integrity and trap type. We have identified 38 potential storage sites with burial depths between 800 m and 4500 m, reservoir capacities (P50) above 5 Mt CO2 and suitable sealing units. The estimated cumulative static storage capacity percentiles of these structures range between P10 = 902.08 Mt and P90 = 5508.93 Mt, with P50 = 2554.10 Mt. We expect the best storage conditions on the West Schleswig Block, where salt-controlled anticlines with moderate burial depths, large reservoir capacities and limited lateral flow barriers are the dominant trap types. Relatively poor storage conditions can be expected for small (P50 < 5 Mt CO2), deeply buried (> 4500 m) and structurally complex potential storage sites in the Horn and Central Graben. Our study highlights the most prolific reservoirs and discusses the most suitable locations for further exploration.