库车坳陷东部凝析油特征及其成藏意义

利用原油物性、族组分、轻烃组分、碳同位素、生物标志化合物等实验资料，系统分析了库车坳陷东部凝析油的物性和有机地球化学特征，厘定了凝析油的成因类型 ，并在此基础上明确了油气充注历史。研究结果表明：库车坳陷东部凝析油属于典型的陆相油，具有密度低、粘度低、凝固点低、含硫低和含蜡中等的特征，碳同位素关系以及生物标志化合物特征表明 凝析油主要来自三叠系湖相烃源岩。库车坳陷东部凝析油和天然气具有不同源、不同期的特征，凝析油主要为湖相烃源岩在成熟演化阶段的产物，天然气主要为煤系烃源岩在高-过成熟演化阶段的产物 ，凝析油的成熟度低于天然气的成熟度，且早期原油遭受气洗改造作用。因此，库车坳陷东部总体上具有“早油晚气”的充注特征，现今的凝析油是早期形成的原油被气洗改造而形成的。

Characteristics of Condensate Oil and Its Significance for Hydrocarbon Accumulation in the Eastern Kuqa Depression

Based on the the experimental data of physical properties, components, light hydrocarbon components, carbon isotope and biomarker, physical properties and geochemical characteristics of condensate oil in the eastern Kuqa Depression,were systematically analysed. Genetical type of condensate oil and hydrocarbon charging history were confirmed. The results show that condensate oil in the eastern Kuqa Depression is typical continental oil, which is featured by low density, low viscosity, low freezing point, low sulfur content and medium wax content. Relationship between carbon isotope and biomarker indicates that condensate oil is mainly derived from Triassic lacustrine source rocks. Condensate oil and natural gas in the eastern Kuqa Depression have different origins. The condensate oil is mainly derived from the mature lacustrine source rocks, and natural gas is originated from mature to post-mature coal-measure source rocks. The maturity of condensate oil is lower than that of natural gas, and early oil suffered from gas washing. Therefore, the eastern Kuqa Depression has the charging feature of ‘early-stage accumulation of oil and late-stage accumulation of gas’. Todays condensate oil is early accumulating oil which undergone gas washing.