| dc.description.abstract | This thesis addresses how minor faults affect CO2 migration. To achieve this goal, the study combines a detailed seismic interpretation of an isolated fault (F1) located in the Aurora CO2 storage site, complimented with detailed mapping of outcrop faults exposed in the Floy Canyon in the foothills of the Book Cliffs (Utah, SW USA). The Aurora CO2 storage site in the Horda Platform (northern North Sea) represents the Northern Lights project's current target for CO2 storage. Due to the dip of the storage unit, buoyant CO2 injected into well 31/5-7 is expected to migrate north and first encounter the smaller scale fault F1. Significant uncertainties exist around the influence of faults on the migration of a CO2 plume: hereunder fault interpretation strategies, limitations in seismic resolution, and input parameters in reservoir modelling. Therefore, detailed assessment of faults in outcrops provide a better understanding of how faults in the subsurface may influence fluid migration pathways. Evaluating the sealing capability of fault outcrops combined with methods used to assess across-fault juxtaposition and membrane seal in the context of seismic data, offer a powerful blend to test the reliability of today's methods in subsurface reservoir seal assessment. Results from the Floy Canyon area show that the five selected faults display a distinct structural geometry and spatial distribution of structural elements that can be classified into fault facies categories (discrete structures, membranes, and lenses), which cannot be resolved in seismic data. The extensional faults in Floy Canyon are considered an analogue to the F1 fault in Aurora due to similar throw magnitudes and depositional environment. The fault facies sealing evaluations show varying results, such as two faults containing sand lenses that can allow across fault fluid pathways. Simple Shale Gouge Ratio (SGR) calculation at a point in each fault of Floy Canyon show that three out of five faults' SGR sealing probability fit the outcrop fault facies sealing evaluation, whereas two faults challenge the SGR predictions. The latter structures offer possible migration routes within the fault core despite a juxtaposition seal being present. In conclusion, SGR techniques to predict fault-seal probability in the surface comply with a very general framework for the fault. Adding fault facies analogues into the discussion nominate certain points and zones in the fault which fluids may flow along and bypass the structure. | eng |