Application of tricyclic terpanes in biodegraded oil-source correlation in Biyang Sag

Biodegraded oils from the northern slope of the Biyang Sag were analyzed to examine the application of tricyclic terpanes to biodegraded oil-source correlation. Tricyclic terpanes are resistant to biodegradation (biode-gradation rank 8) . New tricyclic terpane parameters, such as (C₂₃-C₂₆/C₁₉-C₂₂)-tricyclic terpanes, (C₁₉-C₂₆/C₂₈-C₂₉)-tricyclic terpanes and (C₁₉-C₂₆)-tricyclic terpanes/C₂₉-Ts are effective oil-source correlation parameters. Correlation results suggested that the biodegraded oils in the lower member of Eh₃ on the northern slope of the Biyang Sag came from the mudstones in the lower member of Eh₃ of the central sag, and the oils in the upper member of Eh₃ mainly came from the mudstones in the upper member of Eh₃ of the central sag. The correlation results of oils and source rocks in the ZhuⅠ Depression of the Pearl River Mouth Basin determined by the three tricyclic terpane parameters were consistant with previous results, further supporting the effectiveness of the parameters.