Abstract:

It is difficult to identify the characteristics of the different level biodegraded oil in Gucheng and Jinglou of the west of Biyang Sag oil by most of the saturated hydrocarbon biomarker parameters，such as the organic matter input，depositional environment and maturity of organic matter etc，and also the classification of the biodegraded oil can not be established well for this area.The aromatic compounds of 11 oil samples from the area are tested by using GC-MS analytical technique.The geochemical characteristics of aromatic hydrocarbon fraction in biodegraded oil are analyzed in detail.The results show that the biodegraded oils from the west area of Biyang Sag can be divided into two types by the component of aromatic hydrocarbon of the oil and the relation of triaromatic sterane （C20+C21） /∑（C20~C28） and triaromatic sterane C20/（C20+C28R） of crude oils.It is the same with the result by the relation of triaromatic sterane （C20+C21）/∑（C20~C28） and C24 tetracyclic terpane/C26 tricyclic terpane of crude oil.The relative level of thermal maturity of these two types of biodegraded oil is assessed by the triaromatic sterane parameters.The triaromatic sterane parameters may have significance in several aspects such as oil genesis and maturity evalution etc.

Key words: aromatic compounds, triaromatic steroid, maturity, biodegraded oil, Biyang Sag