塔中北坡SH9井区柯坪塔格组下段原油地球化学特征

塔中北坡SH9井区在柯坪塔格组下段首次发现了中—轻质黑油，具有低粘度、低含硫、低凝固点、高含蜡等特征。族组分中总烃含量、饱芳比均较大，碳同位素轻，小于-31‰。正构烷烃总体为单峰、前峰型分布，正构烷烃保存相对完整，但有轻微的“鼓包”（UCM峰），具有轻微生物降解的特征；CPI值为1.04~1.05，Pr/Ph值为0.84~0.94，不具备奇偶优势，有明显的植烷优势。规则甾烷均呈“V”字形分布，C₂₈20R甾烷相对含量小于25%，C₂₉甾烷含量高于C₂₇甾烷，重排甾烷、升孕甾烷和孕甾烷的相对含量较高。三环萜烷系列的丰度高于藿烷系列，并在三环萜烷中表现为C₂₃三环萜烷的丰度优势，伽马蜡烷含量也较高。原油具有硫芴优势，三芳甲藻甾烷和甲藻甾烷欠发育；成熟度指标表征其为成熟油。认为该原油主要来源于中、上奥陶统烃源岩，中、下寒武统烃源岩贡献不明显。 

Geochemical characteristics of crude oil from lower Kalpintag Formation in SH9 well area, northern slope of middle Tarim Basin

In the lower Kalpintag Formation in SH9 well area in the northern slope of the middle Tarim Basin, medium-light black oil has been discovered for the first time and is characterized by low viscosity, low sulphur content, low pour point and high wax content. The total hydrocarbon content and the saturated/ aromatic hydrocarbon ratio are high, while the carbon isotope is light, usually less than -31‰. Normal alkane totally shows the features of single peak and front peak types. The preservation of normal alkane is relatively complete with slight “drum kits” (UCM peak), showing slight degradation characteristics. The CPI value is 1.04 ~ 1.05 and the Pr/ Ph value is 0.84 ~0.94. Normal alkane has no odd-even predominance and has apparent phytane advantage. Regular sterane shows “V” type distribution. The relative content of C₂₈20R sterane is less than 25% and the content of C₂₉ sterane is higher than that of C₂₇ sterane. The relative contents of rearranged sterane, ascending pregnane and pregnane is relatively higher. The abundance of tricyclic terpane series is higher than that of hopane series, and the C₂₃ tricyclic terpane has abundance advantage in tricyclic terpane. The content of gammacerane is also higher. In the crude oil, sulfur fluorine is rich while triaromatic dinosterane and dinosterane are lack. Maturity parameter shows that the oil is mature. The Middle and Upper Ordovician serve as the main sources while the Middle and Lower Cambrian contribute little.