王芳+包建平+朱翠山

摘要：依据珠江口盆地惠州凹陷不同类型原油样品中各类生物标志物分布与组成特征的分析结果，可以将其划分为煤成油和湖相油两大类。以HZ921井为代表的煤成油表现出强烈的姥鲛烷优势，C19～C26三环萜烷系列相对丰度呈现阶梯状依次降低，C24四环萜烷相对丰度远高于C26三环萜烷，藿烷系列C29降藿烷和C31升藿烷较为丰富，新藿烷（Ts和C29Ts）含量很低，甾烷组成中C29规则甾烷和重排甾烷占绝对优势，这与典型煤成油的分子地球化学特征一致。湖相油中姥鲛烷优势较弱，C19～C26三环萜烷系列呈现以C21为主峰的正态分布，C24四环萜烷丰度与C26三环萜烷丰度相当，新藿烷和重排藿烷含量中等，伽马蜡烷含量极低，2甲基藿烷与C304甲基甾烷十分丰富且存在正相关关系。它们可以作为鉴别研究区原油成因类型的主要依据。

关键词：有机地球化学；原油；生物标志物；链烷烃；萜烷；甾烷；惠州凹陷；珠江口盆地

中图分类号：P618.130.2；TE122.1+13文献标志码：A

Comparison of Geochemical Characteristics of Two Kinds of Crude Oils in Huizhou Sag of Pearl River Mouth Basin

WANG Fang1，2， BAO Jianping1，2， ZHU Cuishan1，2

（1. Key Laboratory of Oil and Gas Resource and Exploration Technology of Ministry of Education，

Yangtze University， Wuhan 430100， Hubei， China； 2. School of Earth Environment and

Water Resources， Yangtze University， Wuhan 430100， Hubei， China）

Abstract： Based on the distributions and compositions of various biomarkers from different crude oils in Huizhou sag of Pearl River Mouth Basin， they can be classified into coalderived and lacustrine oil. The coalderived oils from well HZ921 have the characteristics of higher Pr/Ph value （more than 4.5）， abnormally abundant C24 tetracyclic terpane， steplike decreasing pattern for C19C26 tricyclic terpanes， more abundant C29 norhopane and C31 homohopane， lower neohopanes in C27C35 hopanes， and absolutely predominant C29 rearranged and regular steranes in C27C29 steranes. These features are the main indicators to discriminate coalderived oils from other oils. However， for lacustrine oils， their Pr/Ph values are relatively low （less than 3.0）， the abundances of C24 tetracyclic terpane and C26 tricyclic terpane are similar， the distribution of C19C26 tricyclic terpanes is normal with the main peak of C21， neohopanes and rearranged hopanes are moderate， gammacerane index indicating paleosalinity is very low. It is noted that 2methylhopanes and 4methylsteranes indicating cyanobacteria and dinoflagellate input are very abundant respectively， and the variation of their relative abundances has a normal correlation， representing a specific ecosystem condition to be suitable for the growth of two kinds of microbes. They have an important role in oilsource correlation.

Key words： organic geochemistry； crude oil； biomarker； chain alkane； terpane； sterane； Huizhou sag； Pearl River Mouth Basin

0引言

图1珠江口盆地构造划分

Fig.1Tectonic Units of Pearl River Mouth Basin

珠江口盆地是中国重要的含油气盆地之一，已发现了众多的油气田和含油气构造，惠州凹陷是珠一坳陷一个富油凹陷。油气勘探实践表明，惠州凹陷油层主要分布在珠江组和珠海组，文昌组湖相泥岩和恩平组煤系源岩是其主要生油岩系[16]，它们对已发现油气均有贡献[78]。大量文献涉及了珠江口盆地油源研究[819]。研究结果表明，惠州凹陷原油分为3类，分别来源于文昌组湖相烃源岩、恩平组煤系烃源岩及前两者的混源油。……