Total organic carbon (TOC) enrichment and source rock evaluation of the Upper Jurassic-Lower Cretaceous rocks (Barents S
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ORIGINAL PAPER
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 Francesco Cappuccio1 · Massimiliano Porreca2 · Kamaldeen Olakunle Omosanya3,4 · Giorgio Minelli2 · Dicky Harishidayat3 Received: 11 May 2020 / Accepted: 27 September 2020 © Geologische Vereinigung e.V. (GV) 2020
Abstract 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. Keywords Source rock evaluation · Barents sea · TOC · HI · DlogR · Passey
Introduction
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00531-020-01941-6) contains supplementary material, which is available to authorized users. * Francesco Cappuccio [email protected] 1
Department of Geology, University of Otago, P.O. BOX 56, Dunedin 9054, New Zealand
2
Dipartimento Di Fisica E Geologia, Università di Perugia, Perugia, Italy
3
Department of Geoscience and Petroleum, Norwegian University of Science and Technology (NTNU), 7491 Trondheim, Norway
4
Timelapsgeo, Stiklestadveien 1, 7041 Trondheim, Norway
The characterization of source rocks is one of the most important steps in the evaluation of hydrocarbons generation potential (Peters and Cassa, 1994). A source rock can be described as a fine-grained rock with
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