Isotope heterogeneity in ethyltoluenes from Australian condensates, and their stable carbon site-specific isotope analysis
Abstract
Low-molecular-weight (LMW) aromatic compounds from petroleum fluids have not been widely studied for fluid-source correlations due to their volatility and their relatively low abundances in source rocks. However, LMW aromatics are important components in fluids, including condensates which lack biomarkers (molecular fossils typically used for correlation studies). Here, we have investigated the distribution of ethyltoluenes (o-ET, m-ET and p-ET; ortho, meta and para, respectively) in fluvial-deltaic condensates which contain relatively high abundances of the meta- isomer. The meta-selectivity found in these petroleum fluids is consistent with a mineral catalytic effect on the molecular distribution of these compounds, as it occurs during the clay-catalyzed synthesis of ethyltoluenes. Isomers differ up to 6‰ in δ^(13)C values. Condensates from the Northern Carnarvon Basin, North West Shelf of Australia (NWS), have been analyzed by compound specific isotope analysis (CSIA) by GC-ir-MS, and site-specific isotope analysis (SSIA) using a Q-Exactive-GC Orbitrap^(TM)-based mass spectrometer. The SSIA revealed a ^(13)C enrichment at the methyl end of the ethyl branch of m-ET, following a normal kinetic isotope effect during thermal maturation (cleavage). Continuous development of this first SSIA application will make possible high resolution analysis of light aromatics to outline the evolution of the organic matter to hydrocarbons in petroleum systems.
Additional Information
© 2019 Published by Elsevier. Received 25 March 2019, Revised 31 May 2019, Accepted 10 June 2019, Available online 13 June 2019.Additional details
- Eprint ID
- 96392
- Resolver ID
- CaltechAUTHORS:20190613-135632195
- Created
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2019-06-17Created from EPrint's datestamp field
- Updated
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2021-11-16Created from EPrint's last_modified field
- Caltech groups
- Division of Geological and Planetary Sciences