Integrated Characterization of the Faulted Caprock Shales of the Longyearbyen CO₂ Lab

The quantification of risk inherent to fluid leakage through faults and fractures remains a challenge for underground waste storage. Outcrop analogue studies provide quantitative information pertinent to sealing capacity and help constrain fluid migration modelling and risk assessment. We present an integrated characterization of the Agardhfjellet Formation. The mudstone-dominated, heavily faulted caprock sequence crops out near Janusfjellet, central Spitsbergen, approximately 15 kilometres north of the Longyearbyen CO₂ Lab well park where the formation has been fully cored through four boreholes. Time-equivalent Late Jurassic-Early Cretaceous stratigraphic intervals are widespread across the Barents Sea and Norwegian continental shelf, acting as both prolific source rocks and top seals of several hydrocarbon fields. We supplement the Longyearbyen CO₂ Lab's archive of drill cores, borehole and multiphysical data with a high-resolution outcrop model and ERT/IP data to ascertain seal quality of the heavily faulted caprock. The outcrop model features sub-decimeter root-mean-square-errors and a sub-centimeter resolution, capturing the exposed faults and fractures in full. Cross-cutting faults are observed, offset by as much as 8.5 meters, and fault core architecture change considerably throughout the section. Fault core architecture observations correlate with electrical resistivity tomography and induced polarization results., further constraining fault architecture into the subsurface.