ABSTRACT: Biomarker Geochemistry of Triassic and Upper Jurassic Organic-Rich Shales and Associated Oil Staining, Barents Sea and Svalbard

LEITH, T. L., H. M. WEISS, and L. SCHOU, IKU (Continental Shelf and Petroleum Research Institute), Trondheim, Norway

Triassic and Upper Jurassic organic-rich shales represent important potential hydrocarbon source rocks in the Barents Sea area and many neighboring Arctic sedimentary basins. Biomarker data from outcrop samples, shallow core samples, and exploration well samples have been used to investigate the origin of oil staining on the Loppa High and Nordkapp Basin areas of the Norwegian Barents Sea.

The samples examined covered a wide range of maturities equivalent to vitrinite reflectances from 0.3 to 1.2%, and included artificial hydrous pyrolysis oils. Analysis of the available maturation data indicated that several source-independent maturation indicators could be applied to these shales. These indicators appeared to remain valid for most of the hydrous pyrolysis oils, with the exception of oils produced from highly immature rocks.

The biomarker composition of Triassic organic-rich shales on Svalbard and the Loppa High showed significantly less variation than data from the Upper Jurassic shales, although deposition of the latter was concentrated over a shorter time interval. This variation was attributed to a generally greater input of terrestrial matter in the Upper Jurassic shales. Principal component analyses were employed to aid recognition of oil staining from Triassic and Upper Jurassic sources.

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)