Active Structural Growth Controls Reservoir Distribution of Upper Jurassic Slope Systems, South Viking Graben, Northern North Sea

Jackson, Christopher Aiden-Lee¹, Eirik Larsen², Sigmund Hanslien², Anne-Elise Tjemslund² (1) Imperial College London, London, United Kingdom (2) Statoil ASA, Stavanger, Norway

Upper Jurassic slope systems form the reservoir in a large oil field located in the South Viking Graben, Northern North Sea. Seismic isochrons indicates two main growth faults, which younged progressively landward, developed on the slope during deposition of the slope systems. Seismic data is not of sufficient resolution to map individual depositional elements, however, and biostratigraphy, core and wireline data must be used to determine the sedimentary response of the slope systems to active structural growth. Based on these data three slope systems are identified, the oldest of which comprises thick, amalgamated turbidites, which and are restricted to the hangingwall of the earliest, most basinward growth fault. The middle slope system is more areally extensive than the underlying system, sealing the most basinward growth fault which had become inactive by this time, and extending upslope into the hangingwall of a now-active updip growth fault. The youngest slope system is the most areally extensive of all, being deposited when all the slope growth faults had become inactive and the slope topography had been almost fully healed. By combining seismic and well data it is clear that the landward migration of active growth faults and the expansion of associated depocentres led to progressive unconfinement of slope systems through time. Accordingly, reservoirs units become more unconfined and areally extensive, but less amalgamated (i.e. lower net-to-gross) upwards. This study demonstrates that active structural growth and change in slope accommodation can markedly affect the distribution and internal architecture of reservoirs hosted in turbidite-fed slope systems.