下扬子黄桥-句容地区二叠系-下三叠统油源分析

Oil-source Analysis of Permian-lower Triassic Crude Oils from Huangqiao and Jurong Area in Lower Yangtze Region

下扬子黄桥-句容地区二叠系-下三叠统烃源岩基本进入成熟阶段,部分进入高成熟、甚至过成熟阶段,常规生物标志化合物特征基本趋同,如Pr/Ph值基本分布于0.8-1.55之间,C27、C28和C29规则甾烷基本呈“V”形分布,三环萜烷以C23为主峰,C20、C21含量较低,伽马蜡烷、孕甾烷和升孕甾烷相对丰度均较高,无法用作油源分析。而烃源岩和原油（或油砂抽提物）中稳定碳同位素组成、三芳甾烷系列参数、Ts/17α-藿烷和苝的分布特征存在较大差异,可以依据这些差异进行精细的烃源岩和原油的地球化学对比。依据稳定碳同位素组成特征、三芳甾烷系列参数、Ts/17α-藿烷、苝的相对丰度,将原油划分为3类（Ⅰ、Ⅱ、Ⅲ）。油源分析表明：黄桥、句容地区二叠系龙潭组储层中的成熟原油（Ⅰ类）主要来自二叠系大隆组、孤峰组烃源岩;句容地区三叠系葛村组和部分下三叠统青龙组储层中的高熟原油（Ⅱ类）主要来自二叠系龙潭组泥质烃源岩;青龙组储层中的低熟原油（Ⅲ类）主要来自三叠系青龙组烃源岩,但不排除有二叠系栖霞组烃源岩的油源贡献。

The evolution of Permian--Lower Triassic source rocks in Huangqiao--Jurong areaa of Lower Yan- gtze region had entered the mature, highly mature and even over mature stage, so some conventional geochemical parameters all showed converging characteristics which could not serve as effective index in oil-source analysis. For example, the value of Pr/Ph was between 0. 88 - 1.55, C27 ,C2s and C29 regular steranes presented the ＂V＂ distri- bution pattern, the summit peak for tricyclic terpanes was C23 while the C20 and C21 showed a relatively lower con- tent, and the richness of gamacerane, pregnanes and homopregnane was relatively high. However, differences still existed within the parameters such as ～13C, triaromatic differences, the geochemical characteristics of the source steranes, Ts/17α-hopane and perylene. Based on these rocks and crude oil were studied, and the crude oil was classified into three kinds （ Ⅰ、Ⅱ、Ⅲ ）. The oil-source analysis results indicated that the mature oil in Permian Longtan Formation of the area came from the Permian Dalong and Gufeng Formation; the over mature oil in Creta- ceous Gecun Formation and Triassic Qinglong Fornation sourced from the Permian Longtan Formation; the immature oil in Triassic Qinglong Formation was generated by Triassic Qinglong Formation at both immature and mature sta- ges, but the Permian Qixia Formation may also serve as its source rocks.