The lower cretaceous chalk play in the Danish Central Trough

The Upper Hauterivian to Lower Albian strata of the Danish Central Trough comprise a varied succession of pelagic coccolith chalks, argillaceous chalks and marlstones with subordinate claystones. Where well developed, such as in the recently released North Jens-1 well, the reservoir-quality chalks form three distinct packets, separated by marlstone-dominated intervals. The latter include the dark, organic-rich markers, the Munk Marl Bed (Middle Barremian) and the Fischschiefer Member (Lower Aptian), which are widely recognized in NW Europe. The internal construction of the chalk play is also strongly influenced by unconformities, often of regional significance, which commonly define the boundaries of the individual chalk packets. Lateral variation in the stratigraphic development of these unconformities results in local truncation or absence of individual chalk units. Preliminary sequence stratigraphic analysis suggests that the stratigraphic development of the Lower Cretaceous chalk play in the Danish Central Trough resulted primarily from sea-level changes, although climatic changes during Barremian and Aptian times may have influenced carbonate production and siliciclastic supply. Gross thickness distribution patterns were controlled by local variation in subsidence and active inversion tectonism.