Source Rocks at Svalbard: An Overview of Jurassic and Triassic Formations and Comparison with Offshore Barents Sea Time Equivalent Source Rock Formations

Abstract

The Svalbard Archipelago, located in the Arctic region, holds source rocks of great importance to the understanding of the Barents Sea and the Circum-Arctic. Vast Mesozoic sedimentary successions are exposed on the major islands. The key target of this study was to identify the source rock potential and describe the organic matter (OM) in terms of total organic content (TOC), hydrocarbon potential, facies, and level of maturity in more detail and from more varied localities than previously done. Forty-nine outcrops, mostly shale and mudstone, representing Triassic and Jurassic Formations (Fms) at 4 locations of Svalbard have been analysed geochemically. The results indicate that both Jurassic and Triassic sediments have potential for oil and gas generation, and the best source rocks at Svalbard lie within the Triassic Botneheia Fm. Most samples from the Botneheia Fm at the Blanknuten locality are characterized by high TOC (5–10%) and hydrogen index (HI) (445–609 mg HC/g TOC) values, suggesting excellent source rocks and Type II kerogen. Most samples from the Botneheia Fm at the Muen locality have also very good TOC (2.4–6.2%) but lower HI (124–184 mg HC/g TOC) values, indicating gas prone Type III kerogen. These results suggest that the organic rich Botneheia Fm at Muen has currently lower generating capability than its analogue at Blanknuten and this is mainly attributed to maturation. The Muen samples are also defined by higher production index (PI) (0.1–0.3) and Tmax (448–457°C) values, compared to PI (0.04–0.06) and Tmax (439–446°C) values for the Blanknuten samples. This further suggests that the Muen samples are at a late maturity stage and have probably generated and expelled significant oil, due to their PI values, and that they are still capable of generating gas, while the Blanknuten samples are at an early to mature stage. Biomarker data also support this variation in maturity. The samples from the Upper Jurassic Agardhfjellet Fm at the Agardhbukta locality contained values of TOC (2.2–5.9%), HI (77–121 mg HC/g TOC), and Tmax (452–465°C), implying type III gas prone OM that is presently within the late maturity stage. Isotope and biomarker data suggest marine facies for most samples with input from terrestrial for some Jurassic samples. The presentation includes a comparison between these Triassic and Jurassic Fms and their time equivalent Steinkobbe (1.5–9% TOC) and Hekkingen (3–13% TOC) Fms at the Svalis Dome and offshore Barents Sea.

AAPG Datapages/Search and Discovery Article #90194 © 2014 International Conference & Exhibition, Istanbul, Turkey, September 14-17, 2014