白云凹陷不同相带烃源岩地球化学特征及成藏贡献  

GEOCHEMICAL CHARACTERISTICS OF SOURCE ROCKS IN DIFFERENT SEDIMENTARY FACIES ZONES AND THEIR CONTRIBUTIONS TO THE HYDROCARBON RESERVOIRS IN THE BAIYUN SAG

作　　者：马宁 龙祖烈 柳保军 陈聪 李清泉 MA Ning;LONG Zulie;LIU Baojun;CHEN Cong;LI Qingquan(CNOOC Deepwater Development Ltd.,Shenzhen 518067,China;Shenzhen Branch of CNOOC Ltd.,Shenzhen 518067,China)

机构地区：[1]中海石油深海开发有限公司,深圳518067 [2]中海石油(中国)有限公司深圳分公司,深圳518067

出　　处：《海洋地质前沿》2021年第10期25-32,共8页Marine Geology Frontiers

基　　金：“十三五”国家重大专项“珠江口盆地陆缘深水区油气地质及勘探关键技术”(2016ZX05026-003-006)。

摘　　要：根据烃源岩生物标志化合物、孢粉藻类组合及分析,并结合整体沉积背景,分析白云凹陷不同相带烃源岩的地球化学特征,并确定不同相带烃源岩的成藏贡献。研究表明,文昌组中深湖相烃源岩有机质丰度属于中等级别,有机质类型为Ⅱ_(1)型,来源为藻类等水生生物,其干酪根δ^(13)C值最轻,δ^(13)C值<−28‰。恩平组浅湖相和文昌组浅湖相有机质均来源于陆源高等植物,干酪根δ^(13)C值约为−27‰,有机质丰度属于中等−极好级别,有机质类型为Ⅱ_(2)−Ⅲ型。恩平组海侵湖相烃源岩富海相沟鞭藻及三芳甲藻甾烷,干酪根δ^(13)C值最重,约为−25‰。白云凹陷原油δ^(13)C值主要介于−28‰~−27‰,主要来源于文昌组和恩平组的浅湖相烃源岩,原油类型的分布受沉积相带的控制,个别近洼陷的井存在文昌组中深湖相烃源岩的贡献,恩平组海侵型烃源岩对成藏几乎无贡献。Based on the data of biomarkers,sporopollen and algae assemblages and carbon isotopes of source rocks,combined with the study of sedimentary background,the geochemical characteristics of source rocks in different sedimentary facies zones and their contributions to the formation of hydrocarbon reservoirs in the Baiyun Sag are discussed in this paper.The results show that the abundance of organic matter in the middle and deep lacustrine source rocks of the Wenchang Formation is on a medium level,dominated by the organic matter of type Ⅱ_(1) coming from algae and aquatic organisms,and characterized by the lightest δ^(13)C value of kerogen less than−28‰.However,the organic matters of the shallow lacustrine source rocks of the Enping and Wenchang Formations are from terrestrial higher plants,of which the δ^(13)C value of kerogen is about−27‰,and the abundance of organic matter is on medium to high levels,dominated by type Ⅱ_(2)-Ⅲ of organic matter.The transgressive lacustrine source rocks of the Enping Formation are rich in marine limbic algae and Triaryl dinoflagellate sterane,and the δ^(13)C value of kerogen is about−25‰.The δ^(13)C value of the crude oil in the Baiyun Sag is changed within the range of−28‰~−27‰.It suggests that the crude oil of the Baiyun Sag mainly comes from the shallow lake source rocks of Wenchang and Enping Formations and the distribution of crude oil types is controlled by sedimentary facies.The deep lake source rocks of Wenchang Formation are the main hydrocarbon contributor to the wells near the sag,while the transgressive source rocks of Enping Formation make little contribution to the formation of reservoir.

关 键 词：白云凹陷 烃源岩 碳同位素 油气成因 

分 类 号：P744.4[天文地球—海洋科学] P618.13