Abstract The origin of natural gases, in particular those containing methane (CH4 or C1), ethane (C2H6 or C2), propane (C3H8 or C3) and carbon dioxide (CO2), is commonly interpreted using binary genetic diagrams of δ13C-C1 versus C1/(C2 + C3), δ13C-C1 versus δ2H-C1 and δ13C-C1 versus δ13C-CO2. These diagrams are empirical, but their currently used genetic fields were proposed around 30–40 years ago based on geographically and geologically limited datasets of tens to few hundreds gas samples. As a result, many recently collected gas samples plot outside of accepted genetic fields making these genetic diagrams partly inadequate for the purpose of gas interpretation. Here, we update the genetic diagrams using geochemical and geological data on 20,621 gas samples from a variety of geographical areas (76 countries and territories on six continents) and geological habitats (conventional and unconventional petroleum reservoirs, petroleum seeps and mud volcanoes, gas hydrates, volcanic/geothermal/hydrothermal manifestations, seeps and groundwater in serpentinized ultramafic rocks, aquifers, freshwater and marine sediments, igneous and metamorphic rocks). The revision includes genetic fields for primary microbial gases from CO2 reduction and methyl-type fermentation, secondary microbial gases generated during petroleum biodegradation, thermogenic and abiotic gases. The genetic field of thermogenic gases now includes early mature (δ13C-C1 as low as −75‰) and very late mature (δ13C-C1 around −15‰) gases recently recognized in various petroleum systems. Abiotic C1 is not necessarily 13C-enriched (δ13C > −20‰) as was often considered in the past. The δ13C values of abiotic C1 can be as negative as around −50‰, although a minor component of biotic (microbial or thermogenic) C1 is often associated with abiotic gas. In addition, the diagrams display molecular and isotopic changes that accompany post-generation processes of mixing, migration, biodegradation, thermochemical sulphate reduction and oxidation. The proposed diagrams cover the vast majority of hydrocarbon-containing gases currently known to exist in nature, are the most comprehensive empirical gas genetic diagrams published to date, and thus represent an essential tool for interpretations of natural gases. Still, holistic integration of geochemical and geological data is necessary to better interpret the origin of natural gases and processes that affected their composition.

中文翻译：

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基于超过 20,000 个样本的全球数据集修订的天然气成因图

摘要 天然气的来源，特别是那些含有甲烷（CH4 或 C1）、乙烷（C2H6 或 C2）、丙烷（C3H8 或 C3）和二氧化碳（CO2）的天然气，通常使用 δ13C-C1 与C1/(C2 + C3)，δ13C-C1 对 δ2H-C1 和 δ13C-C1 对 δ13C-CO2。这些图表是经验性的，但它们目前使用的基因场是在大约 30 到 40 年前根据地理和地质上有限的几十到几百个气体样本的数据集提出的。结果，许多最近收集的气体样本位于公认的遗传场之外，使得这些遗传图在一定程度上不足以用于解释气体。在这里，我们使用地球化学和地质数据更新了 20 的成因图，来自不同地理区域（六大洲 76 个国家和地区）和地质栖息地（常规和非常规油藏、石油渗漏和泥火山、天然气水合物、火山/地热/热液表现、蛇纹石化超镁铁质渗流和地下水）的 621 个气体样本岩石、含水层、淡水和海洋沉积物、火成岩和变质岩）。修订版包括来自 CO2 还原和甲基型发酵的初级微生物气体、石油生物降解过程中产生的次级微生物气体、产热和非生物气体的遗传领域。热成因气体的成因领域现在包括最近在各种石油系统中发现的早期成熟（δ13C-C1 低至-75‰）和极晚成熟（δ13C-C1 约-15‰）气体。非生物 C1 不一定像过去通常认为的那样富含 13C（δ13C > -20‰）。非生物 C1 的 δ13C 值可能为负值，约为 -50‰，尽管生物（微生物或产热）C1 的一小部分通常与非生物气体有关。此外，这些图表还显示了伴随混合、迁移、生物降解、热化学硫酸盐还原和氧化等生成后过程的分子和同位素变化。拟议的图表涵盖了目前已知存在于自然界中的绝大多数含烃气体，是迄今为止发表的最全面的经验气体成因图表，因此代表了解释天然气的重要工具。仍然，