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Clumped isotope constraints on the origins of reservoir methane from the Barents Sea

Thiagarajan, Nivedita and Pedersen, Jon Halvard and Brunstad, Harald and Rinna, Joachim and Lepland, Aivo and Eiler, John (2022) Clumped isotope constraints on the origins of reservoir methane from the Barents Sea. Petroleum Geoscience, 28 (2). Art. No. petgeo2021-037. ISSN 1354-0793. doi:10.1144/petgeo2021-037.

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The Barents Sea basin is an oil and gas province containing more than 760 million tons of oil equivalents. The reservoir geology of the Barents Sea is complex due to multiple episodes of subsidence, uplift and erosion, which opened a network of extensional and wrench related faults allowing for fluid migration. The multifaceted geological history complicates efforts to describe the source and characteristics of natural gas in the subsurface Barents Sea. Here we apply stable isotopes, including methane clumped isotope measurements, to thirteen natural gases from five (Skrugard Appraisal, Havis, Alta, Filicudi, and Svanefjell) reservoirs in the Loppa High area in the southwestern Barents Sea to estimate the origins of methane. We compare estimates of methane formation temperature based on clumped isotopes to thermal evolution models for the region. We find that the methane has diverse origins including microbial and thermogenic sources forming and equilibrating at temperatures ranging from 34–238°C. Our clumped isotope temperature estimates are consistent with thermal evolution models for the area. These temperatures can be explained by gas generation and expulsion in the oil and gas window followed by isotopic re-equilibration in some reservoirs due to microbial methanogenesis and/or anaerobic oxidation of methane. Gases from the Skrugard Appraisal, Havis and Alta have methane equilibration temperatures consistent with maximum burial temperatures, while gases from Svanefjell have methane equilibration temperatures consistent with current reservoir temperature, suggesting isotope re-equilibration in the shallow reservoir. Gases from Filicudi on the other hand are consistent with generation over multiple points over its thermal history.

Item Type:Article
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URLURL TypeDescription
Thiagarajan, Nivedita0000-0001-6184-255X
Rinna, Joachim0000-0001-9358-8453
Lepland, Aivo0000-0002-0248-1405
Eiler, John0000-0001-5768-7593
Additional Information:© 2022 The Author(s). Published by The Geological Society of London for GSL and EAGE. Received 26 April 2021; Revised 3 December 2021; Accepted 28 February 2022. We thank Olaf Thiessen, Suzanne Golding and an anonymous reviewer for helpful comments on this manuscript. This work was funded by the Research Council of Norway (Petromaks2-255150). Data availability: The datasets generated during this study are included as tables in the manuscript. Author contributions. NT: formal analysis (lead), writing – original draft (lead), writing – review & editing (lead); JHP: formal analysis (supporting), writing – review & editing (supporting); HB: conceptualization (supporting), funding acquisition (supporting), writing – review & editing (supporting); JR: funding acquisition (supporting), resources (supporting), writing – review & editing (supporting); AL: conceptualization (supporting), funding acquisition (supporting), writing – review & editing (supporting); JE: funding acquisition (supporting), supervision (supporting), writing – review & editing (supporting). The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Funding AgencyGrant Number
Research Council of NorwayPetromaks2-255150
Issue or Number:2
Record Number:CaltechAUTHORS:20220422-928241500
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Official Citation:Nivedita Thiagarajan, Jon Halvard Pedersen, Harald Brunstad, Joachim Rinna, Aivo Lepland, John Eiler; Clumped isotope constraints on the origins of reservoir methane from the Barents Sea. Petroleum Geoscience 2022; 28 (2): petgeo2021–037. doi:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:114414
Deposited By: Tony Diaz
Deposited On:25 Apr 2022 19:07
Last Modified:25 Apr 2022 19:07

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