Biomarker oil-to-source rock correlation in the Western Carpathians and their foreland, Czech Republic

Biomarker analyses indicate that at least two petroleum systems operate in the Vienna basin, Carpathian thrust belt and the European foreland plate in Moravia--one associated with Jurassic and the other with Palaeogene organic-rich rocks. Four oils from the sub-Carpathian foreland plate and one sample from the Vienna basin were analysed and geochemically compared to extracts from Jurassic and Palaeogene source rocks. Two oils from the subthrust foreland plate Lubna-18 and Dolni Lomna-1) are genetically related based on similar geochemical compositions. These oils show high oleanane and 24-nordiacholestane ratios, age-related biomarker ratios that are consistent with an origin from Palaeogene organic-rich rocks. These rocks are inferred to be either the Menilitic shales of the Carpathian thrust belt or autochthonous Palaeogene deposits buried below the thrust belt. Two other oils from the subthrust plate (Zdanice-7 and Damborice-16 correlate geochemically with extracts from Jurassic source rocks in the Sedlec-1 and Nemcicky-1 wells. Like the oil extracts, these oils lack oleanane and show low 24-nordiacholestane ratios, supporting an origin from Jurassic organic-rich marls. The oil sample from the Vienna basin (Tynec-34) appears to be a mixture of the two oil groups.