南海北部深水区古近系沉积体系的东西差异及对烃源岩分布的影响  

Difference between eastern and western Paleogene sedimentary systems in deep waters off the northern South China Sea continental margin and its effect on source rock distribution

作　　者：陈莹 韩银学 边立曾[3] 曾清波 郭帅 纪沫 杨东升 王龙颖 Chen Ying;Han Yinxue;Bian Lizeng;Zeng Qingbo;Guo Shuai;Ji Mo;Yang Dongsheng;Wang Longying(CNOOC Research Center,Beijing 100028,China;Taihe Petroleum Engineering Co.,Ltd.,Xianyang,Shaanxi 712000,China;School of Earth Sciences and Engineering,Nanjing University,Nanjing,Jiangsu 210093,China)

机构地区：[1]中海油研究总院,北京100028 [2]泰和石油工程有限公司,陕西咸阳712000 [3]南京大学地球科学与工程学院,江苏南京210093

出　　处：《石油与天然气地质》2020年第5期1028-1037,共10页Oil & Gas Geology

摘　　要：为了从机制上解释南海北部珠江口盆地深水区和琼东南盆地深水区油气勘探差别大的原因,从盆地结构、物源体系和沉积充填等基础地质条件出发研究两个盆地深水区的成盆、成烃条件,重点聚焦于古近系主要烃源岩发育时期的沉积充填特征,探索其烃源分布模式,为客观评价南海北部深水区资源潜力提供参考。南海北部珠江口盆地和琼东南盆地深水区,早渐新世的沉积体系构成差异大,与当时的盆地结构和物源背景的差别有关。早渐新世是南海北部深水区主力烃源发育期,珠江口盆地深水区为断-坳结构,深水区白云、荔湾凹陷分别具有各自统一的沉积、沉降中心,接受周缘隆起带和盆外古珠江水系的大型物源注入,在海湾环境下发育大型三角洲体系;琼东南盆地深水区为断陷结构,在南北两侧台阶和中央低地发育多排具有一定分隔性的小凹陷群,受海南岛南部水系和越南秋盆河水系等短程物源的影响下,在封闭-半封闭海湾环境里发育障壁海岸体系和一系列小型三角洲。由于沉积体系控制烃源岩的类型和分布,从沉积体系构成差异的角度,探讨了两个盆地深水区烃源分布模式的特点和有利烃源分布区。The striking discrepancy of oil-gas exploration results in deep waters of the Pearl River Mouth and Qiongdongnan Basins in northern South China Sea is rarely interpreted in terms of formation mechanism.With a view to objectively assessing the resource potential of the deep waters off the northern South China Sea,the study analyzes the conditions for basin formation and hydrocarbon generation based on the essential geological factors such as the basinal structure,provenance and sedimentation and charging,with the focus on the main sedimentary characteristics of the hydrocarbon source rock development during the Paleogene,and on the distribution patterns of the source rocks.The two basins are significantly different in terms of their Early Oligocene sedimentary systems,which may be traced back to the different basinal structures and provenances at that time.The major pay source rocks of the deep waters off the northern South China Sea were developed during the Early Oligocene,when the deep-water zone of the Pearl River Mouth Basin was filled with rifts and depressions,and the Baiyun and Liwan Sags in it had their respective depocenters and subsidence centers receiving sediments from surrounding uplift zones and the paleo-Pearl River system outside the basin and developing large delta systems of bay facies.Meanwhile,the deep waters of the Qiongdongnan Basin were a faulted depression with multiple rows of separated small sag groups developed on the terrace of both sides and the central lowlands of the basin.These sag groups subsequently formed barrier-coast systems and small-scale deltas in receiving short-range provenances from waters off the southern Hainan Island and Thu Bon river in Vietnam in a closed-semi-closed bay setting.In all,the sedimentary systems control the types and distribution patterns of the source rocks in the basins,so it is of great significance to the discussion of the distribution patterns and favorable zones of source rocks in the deep waters off the two basins from the perspective of the dif

关 键 词：海陆过渡相 烃源岩 三角洲-海湾体系 物源体系 盆地结构 沉积体系 古近系 南海北部深水区 

分 类 号：TE121.3[石油与天然气工程—油气勘探]