查干凹陷原油地球化学特征与油源对比

GEOCHEMICAL CHARACTERISTICS OF CRUDE OIL AND CORRELATION OF OIL SOURCE IN CHAGAN SAG

查干凹陷是一个中、新生代断陷盆地 ,其原油属低密度、低粘度、低硫中蜡轻质油 ,具饱和烃含量高 (占原油的 80 ～ 90 )、C2 7甾烷丰富等特点。该凹陷发育下白垩统巴音戈壁组二段和苏红图组一段两套烃源岩。甾烷ααα(2 0R)C2 7/C2 9比值 ,类异戊二烯烷烃Pr/Ph ,Pr/nC17比值及碳同位素曲线特征均显示原油与巴音戈壁组二段的白云质泥岩具有较好的亲缘关系 ,而与苏红图组一段深灰色泥岩亲缘关系不明显。因此 。

Chagan Sag is a Meso Cenozoic fault depression.The crude oil in it is of low density,low viscosity,low sulfur content,mid paraffin and lightweight oil characterized by high saturated hydrocarbon contents(800/0～900/0)and rich C 27 sterane.The second member of Bayingebi Formation(K 1b 2)and the first member of Suhongtu Formation(K 1s 1)of the Lower Cretaceous are potential source rocks of the sag.The ratio of ααα(20R)C 27 /C 29 and ααα(20R)C 28 /C 29 of crude oil and the extract from oil bearing sand is 0.39～0.75 and 0.4～0.7 respectively.The ratio of Pr/Ph and Pr/nC 17 is 0.79～0.94 and 0.83～1.34.The carbon isotopic characteristic curve of crude oil is more similar to dolomitic mudstone of K 1b 2 and differs from the dark grey mudstone of K 1s 1.Synthetical correlation shows that the crude oil is mainly derived from the second member of Bayingebi Formation(K 1b 2)dolomitic mudstane.