Abstract: 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.

Key words: Nanyang sag, high-wax oil, biomarker compound, aromatic hydrocarbon, geochemistry