The Jurassic development of the Danish central Graben: High-resolution Stratigraphy, Palaeo-geography and Prospectivity

The backbone of this study is the revised bio-, seismic-, litho- and sequence-stratigraphy for the complete Danish Central Graben. 17 sequences have been mapped out and a similar number of palaeo-geographic maps have been constructed. It is now possible to document, in detail, where and when reservoir sandstones and source rocks were deposited during the Jurassic and lowermost Cretaceous. New areas with reservoir sandstones are presented and organic-rich sediments are identified. The rift system in the Danish Central Graben initiated during the Middle Jurassic as a half-graben, where fluvial sandstones, floodplain and estuarine sediments were deposited along the NW-SE axis of the initial graben, during an overall transgression close to the Ringkøbing-Fyn High. Continued rifting resulted in an overall transgression towards the West and back-stepping Upper Jurassic shoreface sandstones were deposited towards the UK area. Offshore claystones, often very organic-rich, were deposited in the central part of the Danish Central Graben and offshore gravity-flow sandstones and fan delta sandstones were deposited in the easternmost part of the basin, against the Ringkøbing-Fyn High. During the Ryazanian, offshore gravity-flow sand was deposited as well as a widespread organic-rich shale in the central part of the basin.