Triassic Source Rocks of the Barents Sea and Svalbard

Malvin Bjorøy¹, Peter B. Hall¹, Ian L. Ferriday¹, and Atle Mørk^2
1Fugro Geolab Nor AS, Trondheim, Norway.
²Sintef Petroleum Research, Trondheim, Norway.

In the last few years interest in the petroleum potential of the Arctic has become intense. There are several possible source rocks in the Barents Sea area. The most widespread are the marine, Upper Jurassic Hekkingen formation shales. Others, which cover large parts of the region, include Lower-Middle Triassic and Upper Permian shales. There are also some more localised source rocks, of Cretaceous, Upper Triassic to Middle Jurassic and Carboniferous ages.

Triassic deposits are found in most wells drilled in both the Norwegian and Russian parts of the Barents Sea and seismic work has shown that the Triassic succession is found over large areas of the Barents Sea further north than where most wells have been drilled up to the present day. Triassic sediments from most of the exploration wells from the Norwegian sector of the Barents Sea and selected wells from the Russian sector and from outcrops from Svalbard and available oils have been assessed using most conventional petroleum geochemical techniques. The data have been used to assess the source rock potential of the Triassic in the northern areas of the Barents Sea.

The main marine source rock horizons are from the Middle and Lower Triassic. Other paralic deposits with some gas and oil source rock potential are found in the Upper Triassic of both Norwegian and Russian sector wells and from the Middle Triassic in the Russian sector.

Triassic marine source rocks have kerogen type II with HI up to 600 mg HC/g TOC and TOC from 1-12% and S2 from 5-60 mg HC/g rock. The vertical thickness of the good source rock is very variable, being mostly only a few metres thick in the south to many tens of metres on Svalbard. Depositional environments range from highly anoxic, restricted carbonate-rich shales in the Svalbard area, to shallow marine anoxic, predominantly siliciclastic further south. The shales generally yield light to medium range hydrocarbons with relatively low C25+ hydrocarbon contents. In all areas considered here, as with many high palaeo-latitude Triassic source rocks, the Triassic shales are characterised by abundant tricyclic terpanes ranging from C19 to at least C36. At least two of the oil discoveries in the Norwegian sector of the Barents Sea are correlated with Triassic source rocks. The subjects of this study are the richness and organic facies of the different potential source rock units of Triassic age.

AAPG Search and Discover Article #90096©2009 AAPG 3-P Arctic Conference and Exhibition, Moscow, Russia