3D seismic facies and attribute-analysis workflow for CO₂ storage assessment in the Miocene Utsira and Skade sands, Norwegian North Sea

This study applies an attribute-assisted 3D seismic evaluation approach to evaluate CO₂ storage potential in the Miocene Utsira and Skade sandstones above the Patch Bank Ridge (Norwegian North Sea), comparing the proven Zulu Øst structure (Southern Lobe) with an adjacent, previously untested four-way closure (Northern Lobe). Seismic interpretation tied to well 26/10-1 is integrated with seismic facies analysis, RMS amplitude mapping and spectral decomposition (15–28–42 Hz) to constrain reservoir architecture, sediment routing, and containment confidence. Spectral decomposition resolves a SW–NE oriented channel–lobe fairway and channel routing consistent with a basin-floor fan system feeding both closures, supporting a shared depositional framework and comparable seismic facies expression between lobes. Seal assessment using RMS amplitudes above the Top Utsira indicates predominantly low, spatially uniform responses across both prospects; although localised high-amplitude patches and shallow bright-spot anomalies are present above the reservoir, these features are spatially limited and do not define a coherent leakage pathway. Volumetric estimates indicate that storage capacity is dominated by the Skade sands, with combined screening-level capacity across both lobes of ∼43.6–130.6 Mt for storage efficiency factors of 5–15%. Overall, the close match in seismic facies and attribute responses between the proven and untested closures supports promising screening-level reservoir and containment characteristics for the Northern Lobe and demonstrates the value of seismic-attribute workflows for early-stage CCS prospect ranking in data-limited settings.