南海南部北康盆地中中新世深水沉积体类型、特征及意义

MIDDLE MIOCENE DEEP-WATER SEDIMENTS IN THE BEIKANG BASIN,SOUTHERN SOUTH CHINA SEA:TYPES,CHARACTERISTICS AND IMPLICATIONS

利用广州海洋地质调查局已有的2D地震资料,对南海南部北康盆地拗陷阶段中中新世地层内的地震反射结构进行了精细刻画。通过对地震反射同相轴振幅强度、连续性、接触关系、整体形态特征等要素的系统识别和总结,建立了5种典型的地震相类型。结合南海南部沉积盆地的构造-沉积演化特征,识别出了中中新世时期北康盆地内发育的深水沉积体类型,分别是半深海-深海细粒沉积体、三角洲前缘砂体、浊积体和小型浊积体水道。研究认为,三角洲前缘砂体和浊积体构成了研究区拗陷阶段的两大深水碎屑岩储集体类型,能够与下部断陷阶段的烃源岩和中中新世之后的深海-半深海细粒沉积体一起构成垂向上的生储盖组合,具有较好的油气勘探潜力。

2 Dseismic data from Guangzhou Marine Geology Survey are used in this research for the internal seismic architectures of the Middle Miocene in the Beikang Basin,southern South China Sea.Based upon the integrated analyses of amplitude,continuity,contact relationship,and morphologies of the seismic reflections,five typical seismic facies have been identified.The study of the tectono-sedimentary evolution of the basins reveal that there occur bathyal-abyssal fine-grained sediments,deltaic front sandy bodies,turbidites and small-scale turbidite channels in the Middle Miocene of the study area,and deltaic front sandy bodies and turbidites dominate the deep-water clastic reservoirs in the depression stage of the Beikang Basin.The source-reservoir-cap assemblage is well developed by deep rifting stage source rocks,deep-water clastic reservoirs of Middle Miocene,and the bathyal-abyssal fine-grained deposits since Middle Miocene as covers,implying good hydrocarbon exploration potential.