Geological history and petroleum system of the Mittelplate oil field, Northern Germany

Abstract

The geological history of Germany’s largest and most productive petroleum accumulation, the Mittelplate oil field in Schleswig-Holstein (Northern Germany), is reconstructed by simulating the structural and thermal evolution along a 2D cross-section. The Mittelplate field is located at the western flank of the Busum salt dome at the transition from the Schleswig-Holstein mainland to the German North Sea Sector. Organic geochemical data confirm the Lower Jurassic Posidonia Shale to be the predominant oil source rock in the Schleswig-Holstein area. The studied section is characterized by salt walls and salt domes built up by Permian evaporites. Reconstruction of the structural and thermal evolution of the Mittelplate field by means of basin modelling reveals the dominating influence of salt dynamics on the entire petroleum system: The development of secondary rim-synclines during salt rise provided accommodation space for the deposition of the Posidonia Shale as well as the deltaic Middle Jurassic reservoir sandstones. The rise of the nearby Oldenswort salt wall controlled the timing of maturation and petroleum generation during Cenozoic times. Hydrocarbon migration from the Posidonia Shale into the reservoirs occurred up-dip from the deeper subsiding rim-syncline into the structural trap with the Middle Jurassic reservoir sandstones pinching out at the flank of the Busum salt dome. Along the modelled 2D section the field’s recent temperature field and its complex reservoir architecture are reconstructed.