金湖凹陷阜宁组低熟烃源岩饱和烃组成及其生源探讨

Preliminary Study on Saturate Components Characteristics and Its' Origin of Fuling Formation Immature Source Rock in Jinghu Sag

本文应用气相色谱(GC)、色谱—质谱(GC-MS)和线性同位素质谱(GC-C-MS)分析技术对苏北盆地金湖凹陷下第三系阜宁组阜二段低熟烃源岩饱和烃组分及单体烃稳定碳同位素组成进行了深入地研究,发现甾烷类(特别是ααα(20R)-C_(29)甾烷)在饱和烃中含量很高,正构烷烃呈三峰型分布,以nC_(22)或nC_(20)为主峰。最后根据烃源岩有机显微组分和单体烃碳同位素组成特征认为正构烷烃中低碳数(<nC_(19))和中等碳数(nC_(19)—nC_(23))正构烷烃可能主要来源于菌藻类,高碳数(>nC_(23)正构烷烃主要来源于高等植物的蜡质;甾烷类(包括高丰度C_(29)甾烷)大部分可能主要由藻类贡献。

The Saturate components characteristics and its' stable carbon isotope composition of individual n-alkanes of Fuling Formation immature source rock from Jinghu sag in SuBei Basin have been studied in detail by means of GC,GC -MS and GC - C -MS.As a result,the content of steranes(especiallyααα(20R) - C_(29) sterane) of saturate is very abundant.There are three major peaks in the distribution of normal alkanes.The highest peak is C_(22) or C_(20) normal alkane.According to the study of the maceral composition and the variation in stable carbon isotope of individual hydrocarbons,it is proposed that middle molecular weight(nC_(19)-nC_(23)) normal alkanes are derived from bacteria and algae and steranes(including abundent C_(29) sterane) mainly come from algae.