北康盆地为南沙中部海域一重要的含油气盆地。盆地内主要发育了中始新统一第四系地层,最大沉积厚度11000 m。本文通过区域地质背景分析,认为北康盆地位于南沙地块,主体奠基于火成岩带上,盆地基底主要为火成岩及前新生代变质岩。晚始新世以前,南沙地块与华南陆块相连,北康盆地位于古南海西北缘,为一张性拉张盆地,盆地西北大部为陆相环境,东南部为滨浅海环境。晚始新世至早渐新世早期,南沙地块从华南陆块裂离向南漂移,北康盆地成为裂离陆块上的断坳盆地并具走滑特征。随古南海洋壳的被动消减和新南海的扩张,盆地水体加深,除西北尚有陆相沉积外,盆地大部为海相环境。早渐新世以后,南沙地块与婆罗洲地块拼贴,北康盆地整体位于海相环境。本文在详细地震相分析的基础上,对盆地新生界地层划分出三个超层序,7个层序,对上新统以下的5个层序进行了沉积相分析,并编制了平面相图。 Beikang basin is an important petroliferous basin in the central Nansha area. The basin is mainly developed in the mid-Cenozoic Quaternary strata, the maximum deposition thickness of 11000 m. Based on the analysis of regional geological background, this paper argues that the Beikang basin is located in the Nansha block and the main body is based on igneous rocks. The basement of the basin is mainly igneous and pre-Cenozoic metamorphic rocks. Before the Late Eocene, the Nansha block was connected to the South China block. The Beikang Basin was located in the northwestern margin of the South China Sea. It was a stretch-stretching basin. Most of the northwestern part of the basin was continental and the southeastern part was a coastal shallow sea environment. From the Late Eocene to Early Oligocene Eocene, the Nansha block drifted southward from the South China block and the Beikang basin became a fault-depression basin on the fissured block with a strike-slip feature. With the passive subsidence of the South China Sea oceanic shell and the expansion of the new South China Sea, the water bodies in the basin deepened. Most of the basins in the basin are marine environments, except for the continental sediments in the northwest. After the Early Oligocene, the Nansha block collapsed with the Borneo block, and the entire North Beikang basin was located in the marine environment. Based on the detailed seismic facies analysis, this paper divides three super-sequence sequences and seven sequence sequences into the Cenozoic strata in the basin and analyzes the sedimentary facies of the five sequences below the Pliocene. .