Intramolecular carbon isotope of propane from coal-derived gas reservoirs of sedimentary basins: Implications for source, generation and post-generation of hydrocarbons

作者：Xiaofeng Wang, Peng Liu, Wenhui Liu, Changjie Liu, Ying Lin, Dongdong Zhang · 发表于：Geoscience Frontiers · 年份：2024 · DOI：10.1016/j.gsf.2024.101806 · 被引用次数：14 · 研究领域：Hydrocarbon exploration and reservoir analysis、Atmospheric and Environmental Gas Dynamics、Methane Hydrates and Related Phenomena

An intramolecular isotopic study was conducted on natural gases collected from coal-derived gas reservoirs in sedimentary basins of China to determine their position-specific isotope distributions. The propane from the Turpan-Hami Basin exhibited negative ΔC-T (δ13Ccentral-δ13Cterminal) values ranging from −3.9‰ to −0.3‰, with an average of −2.1‰. Propane from the Ordos Basin, Sichuan Basin, and the Tarim Basin showed positive ΔC-T values, with averages of 1.3‰, 5.4‰ and 7.6‰, respectively. Position-specific carbon isotope compositions reveal the precursors and the propane generation pathways in the petroliferous basins. Propane formed from the thermal cracking of Type III kerogen has larger δ13Ccentral and δ13Cterminal values than propane from Type I/II kerogen. The precursor for natural gases collected in this study is identified to be Type III kerogen. Comparing our data to calculated results for thermal cracking of Type III kerogen, we found that propane from the low-maturity gas reservoir in the Turpan Basin was generated via the i-propyl radical pathway, whereas propane from the Sulige tight gas reservoir in the Ordos Basin was formed via the n-propyl radical pathway. δ13Cterminal values covered a narrow range across basins, in contrast to δ13Ccentral. The terminal carbon position in propane is less impacted by microbial oxidation and more relevant to maturity levels and precursors. Thus, δ13Cterminal has a good potential to infer the origin and maturity level of natura...