Master Project Example - Controls on rift margin sediment routing systems in the transition from rift initiation to rift climax: Middle to Upper Jurassic of the Eastern Greater Oseberg Area, Northern North Sea

Most rift basins are characterised by a rift initiation megasequence with distributed depocentres and closely spaced faults, and a rift climax megasequence with broader, linked depocentres often controlled by more broadly spaced larger displacement faults. However, the transition between these two megasequences can be extremely dynamic as faults and their associated depocentres link and interact, and sediment routing systems respond to both local changes in fault-related topography and broader regional changes in rift margin topography and uplift or basinal subsidence and bathymetry. The resulting changes can often produce dramatic changes in sediment thickness, depositional environment and resultant facies which are difficult to image and predict. Understanding this evolution has important predictive implications for the spatial and stratigraphic distribution of potential petroleum play elements, carbon sequestration aquifers or even terrestrially derived pollutants. In the Greater Oseberg Area this transition is represented by the flooding of the Brent delta system during the Bathonian, and a transition to widespread deeper shelfal and deep marine clastics of the Heather and Draupne formations, which are intercalated with discrete sandstone packages fed from local degradation of footwall highs and sediment input from three westward prograding deltaic systems, the ~Bathonian Krossfjord, ~Callovian Fensfjord and ~Oxfordian-Kimmeridgian Sognefjord Formations. The distribution and character of the deltaic systems has been mapped in detail in the Troll and Fram area and has produced some of the Norwegian Continental Shelf’s most prolific hydrocarbon reservoirs, however their distribution south of this are towards Oseberg and in particular towards the Brasse (now Bestla) area and towards the Stord Basin has remained much more elusive. Recent seismic datasets image these systems with a substantial uplift in quality, and it is timely to revisit the evolution of these systems, and their sediment feeder potential towards the Viking Graben, integrated with new biostratigraphy and core sedimentology.