Reconstructing the Quaternary basin configuration and evolution in the central/northern North Sea

REQUBE has contributed to a better understanding of the up to 1000 m thick sedimentary units deposited over the last 2.6 million years (Quaternary) in the northern North Sea. Investigations of material from sediment cores show a cooling of climate until c. 1.5 million years when a rapid increase in sedimentation rates, interpreted as extensive glaciations on the adjacent land areas, occurred. The first evidences of basin wide glaciation are dated to c. 1.1 million years. The results from the investigations of the sediment cores have been integrated with results from analyses of seismic data and used as a basis for modelling of the basin development. The modelling show that Cretaceous and Early Quaternary layers where steeply inclined along the Norwegian west coast before formation of the Norwegian Channel and that rapid sedimentation and uplift must have had profound influence on hydrocarbon reservoirs n the northern North Sea through the Quaternary.

In REQUBE we provide an improved chronological and seismostratigraphic framework of the Pliocene and Quaternary sediments in the Northern North Sea, where backstripping/restoration modelling have been used to study cumulative tilting and the effects of sediment loading. REQUBE have further used sedimentological data, foraminifera assemblages and seismic data to interpret Quaternary depositional environment, and a multiproxy dating approach (amino acid and Sr dating) was utilized to establish the chronology of the investigated sequences. The results obtained through the REQUBE project will contribute to our understanding of migration and maturing of hydrocarbons, the possibility to use the Cenozoic sequences in CCS, and to improve our knowledge of the onset and development of the Quaternary Northern Hemisphere glaciations

The subsidence history of the North Sea Basin during the late Cenozoic is only poorly constrained but has significant implication for further exploration and recovery of deeper hydrocarbon systems. REQUBE is designed to provide parameters of glacial loading, varying glacial-interglacial sedimentation rates, palaeobathymetry and a chronological framework. The cumulative tilting will be the main focus in the backstripping/restoration modelling in addition to effects of relative/eustatic sea level changes and ice loading/unloading. Cumulative effect of erosion/unloading and deposition/loading requires a full source-to-sink focus. To quantify these effects we have to better understand the isostatic effects of these processes, as well as the time involved. On a shorter temporal (time) and spatial (wavelength) scale we will study the effects of glacial loading and unloading through the glacial cycles affecting the area. Backstripping/restoration will continue into pre-glacial times (at least to earliest Oligocene) ? to address basin configuration/topography at the onset of the glaciations and the role of tectonics and climate in the basin evolution. REQUBE will use sedimentological data in addition to foraminifera assemblages and seismic data to interpret palaeo-depositional environment including estimates on palaeo-water depth. Chronology will be determined using a multiproxy dating approach (amino acid and strontium isotope analyses) taking into account reworking and hiatuses within the record. This will also allow REQUBE to answer questions relating to the cumulative effect of uplift/erosion/unloading in the sediment source area and the deposition/loading/subsidence in the basin depocenters (the sink) and whether the additional loads have affected the maturation and migration of hydrocarbons, regional and local tilting of trap, and sealing potential of caprocks and the reservoir quality in the area.