ABSTRACT

The non-hydrocarbon fraction of immature-low maturity crude oils from the western Qaidam Basin which were formed in the source beds deposited in highly saline and strongly reducing environments were analyzed by GC-MS to determine their compositions. Abundant fatty acids, alkanols, fatty acid glycerol monoesters, and stenols were identified. Geochemical analyses suggested that these compounds were largely originated from the oil source rocks. The linear compounds consist primarily of the short-chain homologues (C₁₀–C₂₀). The C₂₇–C₂₉ sterols detected were dominated by C₂₇ stenols. The molecular characteristics suggest that algae and bacteria were the major source organism. The presence of abundant fatty acid glycerol monoesters suggests that the biological lipids, particularly bacterial phospholipids were important contributors to the formation of the crude oils studied. The existence of abundant unsaturated linear compounds, stenols and high CPI values of linear non-hydrocarbon compounds is consistent with the low maturity of these crude oils.