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Abstract

Abstract

Ethane and higher molecular weight hydrocarbons are a substantial fraction of thermogenic hydrocarbons, which are formed in great depth at enhanced temperatures. These processes induce non-methane hydrocarbons to become 13C-depleted in relation to the organic precursor and dependent of the thermal maturity of the source rock. Such isotopic depletions, which are controlled by the higher amount of energy needed to cleave a 12C-12C compared with a 12C-13C bond, are, however, much less pronounced than what a microbial formation of hydrocarbons like methane can induce. Here, strongly fractionating processes can be involved, substantially depleting the product gas of e.g. methanogenesis. This study revisits some published and presents new circumstantial evidences to better understand the processes behind the formation of 13C-depleted (δ13C <-50 ‰ ethane, which is occasionally reported from data sets worldwide. Generally, occurrences and stable isotope signatures of ethane are particularly underreported from sediments and seep gases but also from lab experiments and this “limited ethane-data bias” complicates a good understanding of the background of ethane formation.

EAGE Publications BV © 2020 The Authors © European Association of Geoscientists and Engineers
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/content/papers/10.3997/2214-4609.202333089
2023-09-10
2026-02-09

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