Three episodes of rifting once developed in Beibuwan basin during Paleogene. The first eposode was stronger in the activity of NE-trending faults and controlled the distribution of the Changliu Formation. During the second and third rifting episodes, the activity of NEE-trending faults and EW-trending faults were stronger respectively, and the distribution of Liushagang Formation and Weizhou Formation were controlled respectively. The variations of these three rifting episodes in time and space have resulted in the differences in vertical superimposition of the three Formations in each sag and the areal migration of the sedimentation-subsidence centers. From the fault activities and the formation distribution, the sags in Beibuwan basin can be divided into four types, i. e. the thicker-Changliu, thicker-Liushagang, thicker-Weizhou and persistent-subsidence type, and these types of sags are quite different in resources potential, main occurence interval and accumulation model of hydrocarbon.%北部湾盆地古近纪发育三幕断陷,其中断陷一幕NE向断层活动强度大,控制了长流组地层分布；断陷二幕NEE向断层活动强度大,控制了流沙港组地层分布；断陷三幕近EW向断层活动强度大,控制了涠洲组地层分布.三幕断陷活动具有时空分布上的差异性,这造成了各个凹陷内3套地层垂向叠置情况的差异以及平面上沉积沉降中心的转移.结合断层活动及地层分布,将北部湾盆地凹陷分为厚长流型、厚流沙港型、厚涠洲型及持续沉降型共4类,不同类型凹陷的油气资源潜力、油气主要赋存层位和成藏模式差异很大.
展开▼
