Total organic carbon (TOC) enrichment and source rock evaluation of the Upper Jurassic-Lower Cretaceous rocks (Barents Sea) by means of geochemical and log data

The Barents Sea is a typical example of a multiple sourced hydrocarbon system, with several gas and oil fields. Previous studies have suggested a gas and oil-prone character of the source rocks, but a lack of success in oil discoveries characterizes this area. In this work, the geochemical characterization of source rocks using well data from six exploration wells in the south-western part of the Barents Sea is presented. We studied the Upper Jurassic-Lower Cretaceous Knurr, Hekkingen and Fuglen Fms. mainly formed by shales and mudstones. Here, the Passey's method is applied to characterize the geochemical properties and organic matter of these formations by estimating total organic carbon content (TOC), the quantity of thermally generated hydrocarbons (S2), and hydrogen index (HI). Shale volume was also estimated to check the reliability of the calculated parameters. High shale volume values were found in all the formations, which are generally around 0.8 (volume fraction), indicating a predominance of shaly/muddy lithologies. However, some interbedded sandstones and siltstones are present, together with thinner dolomite and limestone layers. Our results show that Upper Jurassic source rocks such as Knurr Fm., which are often not object of geochemical studies, are mature and characterized by good organic carbon content. Good and very good organic carbon content are measured in the Fuglen and Hekkingen Fms., respectively. The hydrogen index suggests that all the source rocks are mixed gas-oil prone, with the Fuglen Fm. standing out as the most gas-prone between the studied formations. This study demonstrates that the Passey's method can be an alternative to infer geological information when geochemical data are not available.

Automated summary

This study focuses on the geochemical characterization of source rocks in the Barents Sea, showing that some formations have good organic carbon content and all formations tend to be mixed gas-oil prone. The results confirm that the Passey method can be an alternative to infer geological information when geochemical data are not available.