阳信洼陷古近系湖盆复合生烃系统的地球化学特征

陈中红

湖泊科学，2007，19（2）：182-189

古近系沙河街组是阳信洼陷最重要的生烃层段。其湖盆充填具阶段性和沉积演化的旋回性，形成了由沙四段、沙三段与沙一段组成的复合生烃系统和不同的地球化学特征。利用Rock-Eval生油岩评价仪、色谱—质谱仪等实验分析技术对不同层系样品进行了地球化学特征分析研究，其中生烃潜力指标包括有机碳含量（TOC）、残余生烃潜量（S₁+S₂）、氢指数I_H、氯仿沥青“A’’；成熟度指标包括热解峰温T_max、奇偶优势参数OEP、饱和烃轻重比（C₂₁+C₂₂）/（C₂₈+C₂₉）及∑C_21-/∑C₂₂₊、镜质体反射率R_o、莫烷/藿烷及甾烷生物标志物参数C₂₉ββ (ββ+αα)、C₂₉ααα20S（20S+20R）；古环境指标包括异构烷烃参数Pr/Ph、Pr/n-C₁₇、Ph/n-C₁₈及伽马蜡烷等。结果表明，沙四段为弱还原-还原性的半深湖沉积，沉积了一套中等厚度、分布局限的烃源岩（TOC平均为1.5%），其较深位置的烃源岩基本进入成熟阶段，多形成成熟油；沙三段属弱还原-还原性的半深湖-深湖环境，其烃源岩中有机质丰度较高（TOC平均为3.5%），大部分烃源岩处于未成熟-低成熟状态，主要形成未熟油；沙一段为湖水咸化、还原性的半深湖相环境，其烃源岩中有机质丰度高（TOC平均为5%左右），但处于未成熟阶段，主要生成生物气。

Multiplex Hydrocarbon- Generation System in Yangxin Sub-depression and Its Exploration Potential 

Chen Zhonghong,

Journal of Lake Science, 2007，19（2）：182-189

The shahejie Formation of Paleogene System is the most important hydrocarbon generation interval in Yangxin sub-depression. Multiplex-set hydrocarbon generation series of strata being of different geological-geochemical characteristics were formed because of the staging property of the filling and evolution of Paleogene lake basin and the cyclicity of sedimentary process. The organic carbon content, the parameters of pyrolysis and biomarker characters of saturated hydrocarbon was investigated by using the means of Rock-Eval, GC-MS. The Sha-4 hydrocarbon source rocks formed under the semi-saline to saline water environment, the content of organic matter(TOC) was 1.5% averagely, and most of them was being matured and formed into matured oil; The Sha-3 hydrocarbon source rocks formed under the deep-lake environment with fresh-slight saline water, the content of organic matter(TOC) was 3.5% averagely, and most of them was still immature and formed into immature oil; The Sha-1 immature hydrocarbon source rocks formed under the salt lake-saline water environment, the content of organic matter(TOC) was 5.0% averagely, they are formed into biogas.

 Key words: Yangxin subdepression, source rock, hydrocarbon generation system, geochemistry

 

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