Provenance of Brent Group sandstones: heavy mineral constraints

Heavy mineral suites in Brent Group sandstones have been heavily influenced by hydraulic and diagenetic processes in addition to provenance. Geochemical studies of detrital garnet assemblages have shown a great complexity in provenance that argues against a dominant sediment supply northward from an uplifted central North Sea dome. Much of the sediment was fed laterally, particularly in the Broom and Oseberg Formations. The Rannoch, Etive and Tarbert sequences are dominated by similar suites to those in the Oseberg Formation, implying that most of the shoreface and barrier sands were transported longshore from the east. Ness mineralogy is extremely complex. It has a broadly southerly source (possibilities including the southern Shetland Platform and Horda Platform). Close to the western margin of the basin there are strong northern Shetland Platform influences. The lateral and stratigraphic variation in Ness assemblages argues for deposition by several small-scale river systems rather than one single major river. The strong mineralogical variations provide a basis for reservoir subdivision in most of the studied fields, enable the identification of Ness channels that occur at the Etive level, and identify deposits within the Ness sequence that were derived from the barrier sequence into the Ness lagoonal sequence.