东海盆地丽水凹陷原油地球化学特征及其来源分析

Geochemical characteristics of crude oil and oil-source correlation in Lishui sag of East China Sea Basin

丽水凹陷已发现的原油来源复杂,通过对已发现的不同区带原油的地球化学特征的分析,明确了已发现的油气来源。依据原油族组成、轻烃、全烃及萜烷、甾烷等指纹特征,认为丽水凹陷原油在类异戊二烯烷烃、规则甾烷、Pr/Ph等方面存在一定差异,反映其来自不同的油源。可以划分三类来源,其中丽水东次凹轻质油来源于其凹陷内月桂峰组烃源岩,灵峰潜山带轻质油是东、西两个次凹月桂峰组的混合来源;丽水西次凹凝析油也呈现混源油特征,但其主要来自西次凹的月桂峰组和灵峰组的烃源贡献。

Hydrocarbon sources of crude oil are complex in the Lishui sag. In this study we sample geochemical characteristics of crude oil from different areas and identify the oil sources. According to the fingerprint characteristics of crude oil composition such as light hydrocarbons, total hydrocarbons, sterane and terpane finger print characteristics, some differ in, for example, the isoprenoid alkane, regular decane and Pr/Ph value. This suggests that that three different types of oil sources can be identified. The light oil in East Lishui sag is derived from the source rocks of the Yueguifeng Formation, the light oil in the Lingfeng buried hill belt is a mixture of oil from the east and west sag from the Yueguifeng Formation, and the west Lishui sag condensate oil exhibits the characteristics of mixed source oil. However, the main contribution is from the Yueguifeng Formation and the Lingfeng Formation hydrocarbon source.