DISTRIBUTION AND INDICATION OF TRICYCLIC TERPANE IN JURASSIC SOURCE ROCKS AND CRUDE OIL IN CENTRAL SICHUAN BASIN

The distribution characteristics of tricyclic terpenes in biomarkers and their indicative significance for sedimentary environment and biological sources are discussed through the systematic geochemical analysis of source rocks and crude oil samples from Jurassic Da'anzhai Member in central Sichuan Basin by gas chromatography-mass spectrometry (GC-MS). The results show that the Pr/Ph ratios of source rocks and crude oil are medium level, with C₁₉-C₂₆ tricyclic terpenes showing the dominance of C₂₁, low relative percentages of C₁₉₊₂₀ and C₂₃ contents, and C_24TeT/C₂₆TT value greater than 1, indicating that the water was shallow during the sedimentary period of Da'anzhai Member, and the biogenesis was mainly bacteria and algae, with rich mixed-source input of higher plants, which was formed in the weak reduction environment of freshwater lake facies.