白云凹陷烃源岩有机质富集机理  

Organic matter enrichment mechanism of different types of source rocks in the Baiyun sag

作　　者：彭光荣 陈聪 龙祖烈 张丽丽 汪旭东 马勇[3] 辛志源 翟普强 PENG Guangrong;CHEN Cong;LONG Zulie;ZHANG Lili;WANG Xudong;MA Yong;XIN Zhiyuan;ZHAI Puqiang(CNOOC China Ltd.Shenzhen,Shenzhen,Guangdong 518054,China;CNOOC Deepwater Development,Shenzhen,Guangdong 518054,China;State Key Laboratory of Petroleum Resources and Prospecting,College of Geosciences,China University of Petroleum,Beijing 102249,China)

机构地区：[1]中海石油(中国)有限公司深圳分公司,广东深圳518054 [2]中海石油深海开发有限公司,广东深圳518054 [3]油气资源与工程全国重点实验室,中国石油大学(北京),北京102249

出　　处：《地质学报》2023年第12期4164-4178,共15页Acta Geologica Sinica

基　　金：中国海洋石油有限公司“十四五”重大科技项目(编号KJGG2022-0103-03);中海石油(中国)有限公司综合科研项目(编号KJZH-2021-0003-00)联合资助的成果。

摘　　要：白云凹陷古近系文昌组及恩平组烃源岩类型复杂,虽然半深湖相、浅湖相、陆源海相和三角洲相等均有揭示,但有机质富集机理不明,导致对该区烃源潜力及主力烃源岩的认识长期存在分歧。本次研究通过对已钻遇的不同类型烃源岩主微量元素及草莓状黄铁矿粒径特征等分析,剖析不同类型烃源岩有机质发育与保存条件,首次揭示了白云凹陷不同类型烃源岩的有机质富集机理。结果表明:白云凹陷浅湖相烃源岩初级生产力水平较高,文昌组草莓状黄铁矿粒径分布范围为0.4~14.3μm,分布较广,平均粒径为6.8μm,而恩平组烃源岩草莓状黄铁矿粒径分布范围为4.9~15.9μm,平均粒径为8.7μm,整体处于次氧化环境;半深湖相烃源岩初级生产力水平低于浅湖相烃源岩,草莓状黄铁矿粒径分布范围较窄,为5.6~8.0μm,平均粒径为5.8μm,处于硫化-次氧化环境,具有较好的有机质保存条件。陆源海相烃源岩初级生产力水平较低,有机质保存条件较好,接受陆源营养物质输入,有机质较为丰富。三角洲相烃源岩接受大量陆源碎屑的营养物质输入,沉积物堆积效率高,埋藏较快,草莓状黄铁矿平均粒径>7.0μm,且多见自形黄铁矿,处于氧化—强氧化环境,有机质保存条件较差,凭借大量的物源输入和堆积埋藏效率,也可形成有机质富集的有利区域。The source rocks of the Paleogene Wenchang Formation and the Enping Formation in the Baiyun sag are complex.Although the semi-deep lacustrine,shallow lacustrine,terrigenous marine,and deltaic facies have been identified,the mechanism of organic matter enrichment is unknown,leading to long-standing disagreement about the main source rocks in the area and their potential.This study analyzed the main trace elements and the characteristics of strawberry-shaped pyrite grain size in different types of source rocks that have been drilled and analyzed the development and preservation conditions of organic matter in different types of source rocks.It revealed the organic matter enrichment mechanism of different types of source rocks in the Baiyun sag for the first time.The results show that the primary productivity level of shallow lacustrine source rocks in the Baiyun sag is high.The distribution range of strawberry-shaped pyrite grain size in the Wenchang Formation is 0.4~14.3μm with a wide distribution range and an average particle size of 6.8μm,while the distribution range of strawberry-shaped pyrite grain size in the source rock of the Enping Formation is 4.9~15.9μm with an average particle size of 8.7μm;the overall environment is sub-oxidation.The primary productivity level of the semi-deep lacustrine source rocks is lower than that of the shallow lacustrine source rocks,and the distribution range of the strawberry-shaped pyrite grain size is narrow,ranging from 5.6 to 8.0μm with an average particle size of 5.8μm,which is in a sulfide-sub oxidation environment with good preservation conditions for organic matter.The primary productivity level of terrigenous marine source rocks is relatively low,the preservation conditions of organic matter are good,and they receive terrigenous nutrient inputs,resulting in the enrichment of organic matter.The deltaic source rocks received a large amount of nutrients from terrigenous clastic inputs,resulting in high sediment accumulation efficiency and rapid burial.The average g

关 键 词：白云凹陷 初级生产力 有机质保存条件 草莓状黄铁矿 有机质富集机理 

分 类 号：P618.13[天文地球—矿床学]