Faults play an essential role at many potential CO2 storage sites because they can act as conduits or barriers to fluid flow. To contribute to the evaluation of the Aurora storage site in the northern North Sea, we perform a structural characterization and assessment of across-fault seals that displace the Lower Jurassic storage complex. We find that first-order faults are predominately N–S-striking, and W-dipping, with throws greater than the thickness of the primary seal (>85 m). In contrast, second-order faults have lower throws (15–50 m) and variable strike and dip directions. Due to the dip of the storage complex, injected CO2 is likely to migrate northwards before encountering the first-order Svartalv Fault Zone on its footwall side, which juxtaposes the storage units against younger sand-rich units. However, shale gouge ratio values exceed 0.30 at the depth of the storage complex, suggesting that a fault membrane seal may be present. Furthermore, second-order NE-dipping faults create juxtaposition seals and, in places, small-scale structural traps (24–48 m) along the Svartalv Fault Zone. Overall, we suggest that faults within the Aurora storage site could provide barriers to plume migration allowing more CO2 to become trapped, thereby increasing the storage capacity.
This article is part of the Energy Geoscience Series available at https://www.lyellcollection.org/cc/energy-geoscience-series