Petroleum Systems of the Norwegian Barents Sea

Olaf Thiessen

In the Norwegian Barents Sea multiple potential and proven source rocks range from Carboniferous to Cretaceous in age. The main source rocks, however, are of Triassic and Upper Jurassic age. In the Triassic succession source rocks are identified at various different stratigraphic levels. East of a NE-SW line, approximately between the Hoop Graben and the northern Hammerfest Basin, potential source rocks contain dominantly terrigenous organic matter. In the NW of this line organic-rich marine shale is dominating. The source rock thickness, organic matter type and generation potential varies significantly and range from Type IV with no generation potential, over Type III coals or coaly shale with gas potential, to mixed Type II-III and Type II marine shale with good to excellent oil and gas potential. Type I source rocks may be locally developed as well. The Triassic source rocks are oil mature over wide areas of the Norwegian Barents Sea, dry gas to overmature in the deep basins and immature on the Loppa High. The Upper Jurassic – Lower Cretaceous black organic-rich shale of the Hekkingen Formation contains mixed Type II-III organic matter with good to excellent oil and gas generation potential. The Hekkingen Formation is regionally present but may be eroded on structural highs. It is oil to gas mature in the Hammerfest and Fingerdjupet basins and on the eastern rim of the Bjørnøyrenna Fault Complex. The Upper Jurassic is considered as main source for the Hammerfest Basin oil and gas-condensate discoveries. The Hekkingen Formation is immature or very early mature on the Bjarmeland Platform, on the Loppa High, in the Nordkapp Basin and on the Finnmark Platform. Further to the west in the Bjørnøya and the Sørvestnaget basins the Hekkingen Formation is very deeply buried and is dry-gas mature to over-mature at present day. The Hekkingen Formation is an analogue to the Kimmeridge Clay in the North Sea and the Bazhenov Formation source rock in West Siberia. Marine, organic-rich shale of Barremian age is proven in the Kolje Formation in the Fingerdjupet and Hammerfest basins. The kerogen type range from Type I and Type II to mixed Type II/III kerogen and suggest good to excellent source potential for both oil and gas. The thickness of the source rock is in general less than 40m. The Barremian will be immature in most parts of the Barents Sea and is presently dry gas to overmature further to the west in the Bjørnøya and the Sørvestnaget basins. The Barremian source rock may be mature in the northern part of the Hammerfest Basin. Additional source potential is expected from Carboniferous to Permian strata. The organic matter in the Late Palaeozoic succession is dominated by Type III kerogen but mixed Type II/III to I kerogen may be present. Thus, the Carboniferous and Permian source rocks have a significant gas generation potential and a minor potential for oil. These source rocks are mature to post-mature in all parts of the Norwegian Barents shelf.

AAPG Search and Discovery Article #90177©3P Arctic, Polar Petroleum Potential Conference & Exhibition, Stavanger, Norway, October 15-18, 2013