oa Characterization and Comparison of Molecular Compositions of Typical Marine and Terrestrial Crude Oils from Two Basins of Xinjiang, China

Recent advancements in Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS) have enabled detailed analysis of NSO heteroatom-containing polar compounds in crude oil, complementing traditional hydrocarbon characterization. This study employs (-)ESI FT-ICR MS and GC-MS to compare molecular characteristics of terrestrial crude oils from the Yongjin Oilfield (Junggar Basin) and marine crude oils from the Tahe Oilfield (Tarim Basin). Yongjin crude oils, mainly derived from organic matter of higher plants and aquatic organisms in a weakly oxidizing lacustrine environment, show high maturity, multi-stage filling, and severe early-stage biodegradation. Tahe crude oils, sourced from aquatic organisms and algae in a reducing marine setting, also exhibit multi-stage filling and biodegradation, with higher degradation in the central region due to carbonate dissolution structures. Hydrocarbon analysis reveals Yongjin’s dominance of C29 sterane and C23 tricyclic terpane, indicating higher plant input, while Tahe’s biomarkers suggest a low-salinity, sulfur-rich carbonate source. NSO compounds differ significantly: Yongjin is rich in oxygen-containing compounds, reflecting terrestrial plant origins, whereas Tahe contains more sulfur and nitrogen compounds, indicative of marine plankton in a reducing environment. These findings highlight the importance of NSO analysis for understanding complex oil accumulation processes in superimposed basins.