南海西沙海槽盆地新生界含油气系统及油气勘探方向

THE OIL AND GAS SYSTEM AND EXPLORATION DIRECTION IN THE XISHA TROUGH BASIN

为了从整体上认识西沙海槽盆地的油气勘探前景,笔者对该盆地进行了含油气系统分析,认为西沙海槽盆地发育新生界含油气系统,主要烃源岩为始新统湖相泥岩、渐新统海相泥岩;储层为始新统湖相、三角洲、河道砂岩以及渐新统滨浅海相、海相三角洲、深水扇等砂岩;始新统湖相泥岩、渐新统滨浅海相泥岩以及中新世之后的半深海-深海相泥岩构成了三大套区域盖层。西沙海槽盆地新生界含油气系统形成的关键时刻为中中新世,各种油气成藏地质事件具有良好的匹配关系;该油气系统可分为4个油气运聚单元,中央坳陷以及紧邻中央坳陷的北部断阶带、南部坳陷西部局部区域是该盆地进一步勘探的首选区域。本研究成果对认识西沙海槽盆地的油气分布具有一定的参考意义。

In order to reveal the oil and gas exploration prospect in the Xisha Trough Basin,this paper is donated to the oil and gas system of the basin.Research results suggest that Cenozoic oil and gas systems are well developed in the Xisha Trough Basin.Source rocks include the Eocene laustrine mudstone and Oligocene marine mudstone.Reservoirs consist of the Eocene lake deposits,deltaic deposits and channel filling sandstones,Oligocene offshore and shallow marine deposits,marine delta deposits and deep water fan sandstones.The cap rock include three layers:Eocene lacustrine mudstone,Oligocene marine mudstone and Miocene-Quaternary bathyal-abysmal mudstone.The oil and gas system was mainly formed in Miocene in the Xisha Trough Basin,where all the geological events matched very well.The Cenozoic oil and gas system can be further subdivided into four migration and accumulation units.The central depression and the northern fault ladder belt adjacent to the central depression and the west parts of the south depression are the principal exploration targets recommended.