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Slope Turbidite Reservoir Development along a Tectonically Active Margin (Part I) — A Down-System Perspective from the Upper Cretaceous, Offshore Norway

Jackson, Christopher A.*1; Sømme, Tor O.2
(1) Earth Science and Engineering, Imperial College, London, United Kingdom.
(2) Department of Earth Science, University of Bergen, Bergen, Norway.

The northern Norwegian North Sea contains numerous mature hydrocarbon fields that are contained in shallow-marine, Jurassic reservoirs in Jurassic fault blocks. A few smaller discoveries have been made in Upper Cretaceous, Deepwater reservoirs, although the subsurface expression, stratigraphic architecture and trapping styles associated with these reservoir intervals are poorly understood. In the first part of a two-part talk we use seismic reflection, well and core data to: (i) provide a regional synthesis of the subsurface expression of upper Turonian-to-upper Coniacian Deepwater reservoirs along the Møre-Trøndelag margin; (ii) investigate the controls on the evolution of these depositional systems; (iii) illustrate the key trapping styles; and (vi) provide quantitative data on the size and morphology of these depositional systems for the regional source-to-sink analysis that follows in the second part of a two-part talk. Turbidite sandstones represent the best reservoirs; in core, individual beds are up to a few metres thick, but amalgamated units up to several tens of metres thick are common. Sandy-mudstone debrites are observed, but they are of poor reservoir quality and may form barriers or baffles to fluid flow. Synthetic seismograms indicate that sandstone-dominated deposits are expressed on seismic data as packages of high-amplitude reflections. In cross-section these reflections form channelized and mounded packages, which are interpreted as channels/channel complexes and sheet-lobe deposits, respectively. 11 slope fans are recognised and these were fed by sediment that were routed through upper slope canyons incised into the eastern basin margin. Fans may either be ponded behind or overstep intra-basin highs, and the key trapping styles are: (i) stratigraphic, and related to up-dip pinch-out of the fans into slope mudstones; or (ii) structural, and related to differential compaction-related drape of fans across underlying fault blocks. We show that future exploration success in the Upper Cretaceous Deepwater play on the Møre-Trøndelag margin relies on a robust understanding of the seismic expression, sedimentology, stratigraphic architecture and trapping styles associated with turbidite systems deposited on topographically-complex slopes. In our companion talk, we present quantitative data on fan volume, slope lengths and canyon spacing, and use these data to investigate the geometry of the onshore catchments that fed the fans.  


AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California