南阳凹陷高蜡原油的地球化学特征

南阳凹陷原油为低密度、低粘度、低含硫和高凝固点的正常原油,高蜡-特高蜡也是南阳凹陷原油的主要特征。饱和烃含量高,饱和烃/芳香烃值大于3.0.C₂₇—C₂₉规则甾烷均呈“V”字型分布,C₂₉甾烷异构化作用较强,其比值为0.3~0.6.萜烷以五环三萜烷和长链三环萜烷为主,非藿烷系列(尤其是伽马蜡烷)含量相当丰富。个别样品伽马蜡烷指数高达1.3,为高盐度强还原环境。芳香烃组分以菲为优势组分,其次为萘系列,三芳甾烃在张店地区相对较低,且变化幅度较大。

Organic Geochemical Characteristics of High Wax Oils in Nanyang Sag

The crude oil from Nanyang sag is characterized by low density, low viscosity, low sulfur content and high freezing point, being normal crude oil with high-to abnormal high-wax content, high saturated hydrocarbon content, saturated/aromatic hydrocarbon ratio of more than 3.0, V-shape distribution of C27-C29 regular steranes with high isomerization of C29 sterane and the S/R+S ration of 0.3~0.6. The terpane is dominated by penta-triterpanes and long-chain tricycloterpanes; the non-hopane series (especially gammacerane) are quite abundant. The gammacerane index of individual sample is up to 1.3, indicating a high-salinity and strong-reduced environment. The aromatic components are dominated by phenanthrene and then the naphthalene series. The tri-aromatic steroids content of crude oil is relatively low in Zhangdian area and shows a wide range.