东海盆地西湖凹陷不同构造带原油陆源生物标志化合物特征及其指示意义

利用地球化学分析手段，对西湖凹陷黄岩构造带、平北地区以及宁波构造带的16个轻质油样品进行了分析。原油中富含反映陆源高等植物输入的生物标志化合物，尤其是源于被子植物、裸子植物及蕨类植物的三环、四环二萜类及其芳构化产物，而反映水生低等植物输入的生物标志化合物含量较低。不同构造带间原油中这些化合物的分布特征具有明显差异，如异海松烷/nC₂₀、异海松烷/（异海松烷+16β（H）扁枝烷）、1，2，5-三甲基萘/1，3，6-三甲基萘、1，7-二甲基菲/（惹烯+1，7-二甲基菲）等。这些差异指示了宁波构造带与平北地区原油裸子植物输入较多，蕨类植物及被子植物输入较少，而黄岩构造带原油蕨类植物输入较多，被子植物与裸子植物较少的特点。研究中利用全油色谱-质谱将原油饱和烃与芳烃组分建立联系，提出（异海松烷+1，7-二甲基菲）/（惹烯+16β（H）扁枝烷）作为反映西湖凹陷轻质原油生源构成的指标，而该参数与全油碳同位素值的正相关关系证明了裸子植物树脂对西湖凹陷轻质油的重要成烃贡献。 

Characteristics and indication of terrestrial biomarkers of crude oil in different local structures of Xihu Depression,East China Sea Basin

Sixteen light oil samples from Huangyan structural belt, Pingbei area and Ningbo structural belt in Xihu Depression were analyzed by geochemical analysis. The crude oil samples are rich in biomarkers related to the input of terrestrial higher plants, especially the tricyclic and tetracyclic diterpenes and their aromatization compounds derived from angiosperm, gymnosperms, and pteridophytes, while the content of biomarkers reflecting the input of aquatic plants are relatively low. The distribution of these high plant biomarkers between different local structures is obviously different, such as isopimarane/nC₂₀, isopimarane/(isopimarane+16β(H)-phyllocladane), 1, 2, 5-trimethyl naphthalene/1, 3, 6-trimethyl naphthalene, and 1, 7-dimethyl phenanthrene/(retene+1, 7-dimethyl phenanthrene). These differences indicate that there are high contents of gymnosperms input, and low contents of pteridophytes and angiosperms input of crude oil from the Ningbo structural belt as well as the Pingbei area. However, crude oil from the Huangyan structural belt has more pteridophytes input and fewer angiosperms and gymnosperms input. In this study, whole oil gas chromatography-mass spectrometry analysis was used to develop a relationship between saturated hydrocarbons and aromatic hydrocarbons. The ratio of (isopimarane+1, 7-dimethyl phenanthrene)/(retene+16β(H)-phyllocladane) was proposed as an index to reflect the provenance of organic matter of light oil in Xihu Depression, and the positive correlation between the parameter values and whole oil carbon isotope values proves that the gymnosperms have the most important hydrocarbon-generating contribution to the crude oil in Xihu Depression.