Seismic - Stratigraphic framework of the Statfjord Group on the Utsira High
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Sandstones of the Statfjord Group are important reservoir sandstones in the Northern North Sea. However, in the rest of the North Sea the Statfjord Group is underexplored. Sub-regional seismic interpretation on the Utsira High show available accommodation space during the deposition of the Statfjord Group, with increased accommodation space towards the end of deposition of the Group. A variation in the thickness of the Statfjord Group can be observed in the study area, with a thinning of the succession eastwards in the area. This suggests the variations of the Statfjord Group thickness is controlled by available accommodation space, hence the change in base level through time. Seismic horizons and faults show a post-rift Permo-Triassic depositional trend, affected by a later episode of Middle-Late Jurassic rifting and a reactivation of the Permo-Triassic faults. The varying thickness of the group, show the Permo-Triassic faulting generated the structural setting present during the deposition of the Statfjord Group. Regional well correlations and sub-regional seismic interpretations show the Utsira High was a paleotopographic high during deposition of the Statfjord Group. Well data shows continental environment dominated by large floodplains and rivers prevailed during the deposition of the group, with a thin layer of marginal marine deposits overlying the continental strata. High net-to-gross values of the Statfjord Group on the Utsira High indicate a proximity to the source area, but the high is situated a significant distance away from known provenance areas, implying a local source of sediments, possibly remnant rift topography on the high itself from the Permo-Triassic rift event. This suggests the high could divide two different fluvial drainage provinces in Late Triassic-Early Jurassic in the North Sea. Well correlations show differences in thickness and net-to-gross of the Statfjord Group in wells on the Utsira High, in the Viking Graben and Stord Basin, suggesting that available accommodation space during deposition was a controlling factor of sandstone connectivity.