Abstract: The crude oils in Huzhuangji and Qingzuji oilfields in west slope area of Dongpu sag are mainly distributed in Ertajie struc-tural belt between Changyuan (placanticline) fault and Shijiaji fault, with characteristics of low content of saturated hydrocarbons, high content of wax and weight carbon isotope. The GC-MS analysis results show that the isomer ratio of C2 sterane and the ratio of tris-norhopene w(Tsy)wv(Tm) are generally low and similar with the distributing scope of typical low maturity of crude in other basins in China.Also, in aromatic hydrocarbons, the biomarkers reflecting low maturity stage, such as alkyl thiophenes, tetrahydronthiophene and dehy-droxytocopherol series compounds, are detected. Comprehensive analysis indicates that the crude oils found in Huzhuangji and Qingzuji oifelds are all in low maturity rather than in maturity.

Key words: Dongpu sag, west, slope, crude oil, maturity