HYDROCARBON POTENTIAL OF THE KHATANGA-ANABAR REGION (ARCTIC SIBERIA) - WHAT'S GENERATING THE NORDVIK OIL?

The Khatanga-Anabar region on the southwestern edge of the Siberian Laptev Sea is part of a large sedimentary basin, filled with predominantly clastic rocks of Paleozoic to Mesozoic age. The petroleum system of this region is of particular interest also for an evaluation of the shelf of the Arctic Ocean.

Sediments from outcrops of the Khatanga-Anabar region have been sampled for organic geochemical analysis, and a crude oil obtained from an abandoned petroleum production facility at Nordvik as well as five hydrocarbon impregnations from an uplifted reservoir structure cropping out at Tus-Takh have been investigated as well.

Isoprenoid data suggest mixing of terrestrial and aquatic organic precursor types and sterane biomarkers indicate significant contributions of land plant material in most samples, but a dominance of aquatic material in Jurassic/Cretaceous samples from the Pasha area. Biomarker derived terrestrial/aquatic ratios as well as carbon isotope data of bulk organic carbon suggest a similar interpretation, and the abundance of ¹²C in one sample from Nordvik and in several samples from Pasha could indicate a microbial contribution in oxygen deficient waters. Carbonate rich samples at Nordvik are enriched in C₂₉-hopanes, whereas all other samples with low carbonate contents show C₂₉/C₃₀-hopane ratios below unity. Sterane biomarkers indicate a regional variation of thermal maturities. The amount of organic carbon and the quality of the organic matter indicate oil potential for sediments from Pasha and Nordvik and rather gas prone sediments at other areas

The impregnations at Tus-Takh and the crude oil of Nordvik are degraded, although biomarkers seem to be unaffected through degradation, and suggest a single oil family for impregnations and Nordvik crude oil, which is supported by carbon isotope ratios. We suggest from biomarker and stable isotope data that the likely source of the impregnations at Tus-Takh and the crude oil of Nordvik is a sediment obtained from Tus-Takh of proposed Palaeozoic age, the latter suggestion is also compatible with sterane C₂₈/C₂₉ ratios above 1 in extract as well as in crude and impregnations.