Compound-specific carbon isotope analysis of n-alkanes from source rocks and oils from the Paratethyan realm

Martin Sweda

Research output: ThesisMaster's Thesis

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Abstract

The Paratethyan realm extends from Switzerland to Kazachstan and hosts a significant number of petroleum provinces. Many of these provinces have been charged by Mesozoic and Cenozoic source rocks. For this study, 48 extracts of source rocks with Jurassic to Miocene ages and 29 oils from six petroleum provinces have been choosen for compound specific carbon isotope analysis of n-alkanes (CSIA-A) in order to (1) conduct oil-source correlations, (2) investigate the influence of stratigraphy on δ13C composition of n-alkanes, and (3) observe the regional distribution of CSI patterns in Oligo-/Miocene and Mesozoic rocks. Samples were selected from the Molasse Basin (Germany, Austria), the Waschberg Zone (Austria), the Carpathian Fold-and-Thrust belt (Ukraine), the Carpathian Foredeep (Ukraine), the Western Black Sea shelf (Bulgaria), and the Rioni Basin (Georgia). (1) Based on CSI-A patterns and biomarker ratios, the Voitsdorf and Haidenbach oils in the Upper Austrian part of the Molasse Basin could be correlated with the Oligocene Schöneck Formation. In contrast, deviant CSI-A patterns and the absence of oleanane suggest that oil stains in borehole Mank, located in the Lower Austrian part of the Molasse Basin, were produced by a Mesozoic source rock, which could have also generated oils recovered from Triassic rocks in borehole Urmannsau-1 (N. Calc. Alps). Oils from the eastern part of the Carpathian Fold-and-Thrust belt could be correlated with the Menilite Formation. The Jurassic Kokhanivka Formation is not a probable source rock for heavy oils in Jurassic reservoirs from the Mesozoic basement of the Carpathian Foredeep. The Tjulenovo oil (W. Black Sea) produced from Cretaceous reservoir rocks has been generated by either the Oligocene Ruslar Formation, the Oligo-/Miocene Kaliakra Canyon Fill, or both. The Shromisubani oil accumulated in Upper Miocene reservoirs in the Rioni Basin probably represents a mixture of oils generated in Oligocene Maikopian sediments and Eocene sediments of the Kuma Formation. (2) Depth plots of δ13C values of short-, mid-, and long chain n-alkanes of core samples from well Oberschauersberg-1 (Molasse Basin), cuttings samples from well Varna Zapad-1 (W. Black Sea), and outcrop samples from the Martvili section (Rioni Basin) were used to investigate stratigraphic controls on carbon isotopy of n-alkanes. The results show (i) a significant difference in δ13C composition of individual n-alkanes in mid (n-C21) and short chain range (n-C16) between the Schöneck Formation and the overlying units. In contrast, isotope ratios of long chain n-alkanes (n-C26) remain constant at the Schöneck/Dynow boundary and change only at the Dynow/Eggerding boundary. Mid chain n-alkanes of Eggerding Formation and Dynow marl show similar δ13C values. The different behavior of mid & long chain n-alkanes may indicate that the isotopy of the CO2 pool avaialable for land plants and aquatic organisms did not change simultaneously; (ii) in the Kaliakra Canyon Fill and the Ruslar Formation from the Varna Zapad-1 well offshore Bulgaria δ13C values of mid and long chain n-alkanes get lighter with depth. Short chain n-alkanes do not follow this trend. The isotope-depth trend does not continue in the Eocene Avren Formation; (iii) in the Rioni Basin δ13C values of mid and long chain n-alkanes do not show high variation with depth. Short chain n-alkanes on the other hand are significantly lighter in the Kuma Formation than in the Maikop Group. (3) Regional distributions of CSI patterns in Oligo-Miocene and Mesozoic rocks have been illustrated using three paleogeographic maps. An unusual V-shape pattern is observed in samples from the Molasse Basin and the western Black Sea representing Pshekian horizons and the Solenovian Event, and in the Late Solenovian to Early Miocene fill of the Kaliakra Canyon (W. Black Sea).
Translated title of the contributionKomponentenspezifische Kohlenstoff-Isotopenanalyse von n-Alkanen ausgewählter Muttergesteine und Öle aus der Paratethys
Original languageEnglish
QualificationDipl.-Ing.
Awarding Institution
  • Montanuniversität
Supervisors/Advisors
  • Sachsenhofer, Reinhard, Supervisor (internal)
Award date19 Oct 2018
Publication statusPublished - 2018

Bibliographical note

no embargo

Keywords

  • CSIA-A
  • n-alkanes
  • Paratethys

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