@article{Li2026, 
author = {Feng-Jiao Li and Peng Liu and Wei-Wei Yang and Fu-Qi Li and Qian-Ping Wang and Ming-Yang Ma and Wen-Hui Liu and Dong-Dong Zhang and Xiao-Feng Wang},
title = {Kerogen aromatization and late hydrocarbon generation: Evidence from position-specific isotope composition of propane},
year = {2026},
journal = {Petroleum Science},
volume = {23},
number = {5},
pages = {2574-2586},
keywords = {Position-specific carbon isotope, Propane, Aromatization, Longdong area, the Ordos Basin},
url = {https://www.sciopen.com/article/10.1016/j.petsci.2026.01.024},
doi = {10.1016/j.petsci.2026.01.024},
abstract = {Natural gas accumulation involves complex multi-source mixing and post-genetic alterations that can lead to carbon isotopic reversals. Here, we report for the first time the co-occurrence of bulk and propane position-specific (PS) isotope reversals in conventional overmature gas reservoirs. We propose an aromatization-stabilization mechanism to explain these anomalous isotopic patterns. The Longdong area of the Ordos Basin provides a unique natural laboratory due to its well-defined thermal maturity gradient, the presence of multiple source rocks, and the coexistence of gases derived from different kerogen types. Integrated geochemical analyses of Cambrian-Carboniferous gases from six wells, reveal two key findings. First, the natural gases are in the overmature stage and exhibit both bulk carbon isotope reversals (δ13C1 > δ13C2 > δ13C3 or δ13C1 > δ13C2 < δ13C3), and Position-specific carbon isotope of propane anomalies (ΔC-T = δ13Ccenter−δ13Cterminal<0‰; δ13Ccenter: isotopic composition of the central carbon in propane, δ13Cterminal: isotopic composition of the terminal carbon in propane). The propane in natural gas exhibits 25%–50% contribution from the isopropyl pathway. This is a formation mechanism theoretically restricted to low-maturity systems. This indicates preservation of early-formed branched precursors through cyclization/aromatization processes. We establish an “early-aromatization, delayed-cracking” model. This work highlights position-specific isotope analysis as a powerful tool for identifying post-genetic modifications in deep conventional and unconventional reservoirs.}
}