New hydrocarbon systems in the eastern North Sea - Cenozoic basin evolution, seismic inversion and 3-D modelling

The results show that the Cenozoic evolution of the area is consistent with a gradually filling of the depression, which presently contains the post-mid Cretaceous sediments. The origin and evolution of the depression was related to the dynamics of the Middle Jurassic North Sea plume. The general fill of sea level, the post-conpressional rebound of the Sorgenfrei-Tornquist Zone and the activity of glaciers have resulted in significant erosion in the eastern North Sea area. The associated isostatic movements have resulted in a marked NE-SAV tilt of the area, which has exerted significant Control on hydrocarbon migration out of the Central Graben. The heat flow evolution of the area is quiet with no traces of thermal events. However, in areas of significant glacial erosion the present heat flow is augmented. Analysis of the seismic data focused on the formation of Paleocene plays outside the Siri trend and on Oligocene plays. The results show that basin floor topography, controlled by subtle tectonic movements and halokinetics, controlled the temporal and spatial development of interesting plays and possible fairways. The sedimentation history (rates, directions and relative sea level) exerted a major Control on the character of the sediments. Contour parallel currents had a major influence on Oligocene depositional processes. For example, the only known Oligocene find was made in mobilized and redeposited sediments of the Freja Fm. The migration models assume buoyancy driven migration sourced from the Central Graben. Development of the tilt of the migration route, which depends on sedimentation history and paleobathymetry, and the transmissivity are the governing parameters. The most likely scenario predicts late migration to the NF through the Siri trend, but no migration through the Ibenholt Valley