Seismic stratigraphy of the Lower Cretaceous Valhall Formation (Danish Graben, North Sea)

Detailed seismic stratigraphic analysis of a 3D seismic survey covering the southern part of the Danish Central Graben in the North Sea has revealed a complex stratigraphic basin infill pattern controlled by eustacy and local tectonics in the Lower Cretaceous Valhall Formation. The understanding of the stratigraphic architecture of this mudstone formation is critical for the development of the overlaying chalk reservoirs of the Tuxen and Sola Formations. The applied workflow included an application of flattening in order to approximate the Lower Cretaceous basin morphology, the attenuation of multiples generated by the overlying chalk deposits, a systematic use of both 2D transects and horizon slices in the analysis of the depositional geometries and the application of a Relative Geological Time (RGT) model interpretation technology. The results show an asymmetrical infill of the Lower Cretaceous consisting of westward prograding, mud-dominated clinoforms. The overall progradational pattern is clearly expressed in the most southern part of the basin by coast-parallel features interpreted as shelf margin breaks. The asymmetrical paleotopography, created by the muddy shelf of the Valhall Formation, formed subsequently the substratum for the deposition of the chalks of the Tuxen and Sola Formations, and controlled their facies distribution.