潜江凹陷蚌湖向斜带烃源岩特征及生排烃史

Characteristics and Hydrocarbon Generation-Expulsion History of Source Rocks of Banghu Syncline in Qianjiang Depression

在烃源岩分布特征及有机质丰度、类型和成熟度分析的基础上,应用含油气盆地数值模拟技术,定量恢复了主力烃源岩层系的生排烃史。研究表明,蚌湖向斜带潜江组各层系烃源岩均具有较高的有机质丰度,有机碳质量分数平均为0.78%,最高可达11.5%;有机质类型以Ⅰ型和Ⅱ1型为主;但有机质成熟度具有明显的差异,潜一段、潜二段、潜三上亚段烃源岩多处于未成熟—低成熟阶段,潜三下亚段、潜四上亚段和潜四下亚段烃源岩大多已达中成熟—高成熟阶段,是研究区的有效烃源岩层系。潜四下亚段烃源岩的生排烃强度和排烃效率最高,且开始生排烃的时间也最早,是最主要的生排烃层位。凹陷的油气勘探应以潜四下亚段烃源岩为油源、以分布在蚌湖向斜带及其周边的构造和岩性圈闭为主要目标。

In order to better understand the process and mechanism of hydrocarbon accumulation and identify the principal source rocks and hydrocarbon-generation potential of Banghu Syncline in Qianjiang Depression,this study uses the technique of basin modeling to reconstruct the hydrocarbon generation and expulsion history in the study area based on the analysis of source rocks distribution,organic matter abundance,types and maturation.Each source rock of Qianjiang Formation has a high organic matter abundance,better organic types and different maturations.The average content of TOC is 0.78%,with the highest 11.5% in type I and II1 organic matter.The source rocks of Eq1,Eq2 and Equ3 are in the stage of immaturity and low maturity,but others are in the stage of middle maturity and high maturity and effective source rocks in the study area.The hydrocarbon generating or expelling intensity and hydrocarbon expulsion efficiency of Eql4 rock is the highest,and the hydrocarbon generation and expulsion time is earlier,meanwhile Eql4 rock is the major layer to generate and expel hydrocarbon.Therefore,the main oil source should be from Eql4.Besides,structural and lithological traps can be considered as the future exploration target in Banghu Syncline as well as its peripheral areas.