北部湾盆地东南部构造特征及控油作用分析

北部湾盆地发育有与华南陆缘陆相中小盆地相同的基底，大体经历了古新世—始新世断陷、渐新世断拗过渡及中新世以来区域沉降3大演化阶段。受神狐、珠琼、南海以及东沙4次成盆事件影响，盆地东南部福山及迈陈两凹陷发育了4期断裂，形成了NE、NEE与NW共3组优势走向断裂体系，构成了上、下2套构造层；凹陷中断层组合为花状、叠花状、花瓣状、花丛状4种形态，构成了基底掀斜走滑、基底伸展多米诺与盖层伸展拆离、盖层滑动牵引等4种样式；福山凹陷演化表现出有明显的非对称拉伸过程，中部发育有NE向构造转换带。盆地东南部发育的第Ⅳ期近EW向断裂体系是两凹陷今控藏控油的主要断裂体系，由此优选福山凹陷中部鼻状构造带及东南陡坡断阶带作为盆地东南部最有利的勘探区带。

Structural features and controlling on oils in southeastern Beibu Gulf Basin

Similar to those of the middle and small basins of continental margin facies in South China, the basement of the Beibu Gulf Basin has experienced 3 evolutionary stages: rift from Paleocene to Eocene, rift to depression transition during Oligocene, and regional subsidence ever since Miocene. Influenced by the basin-forming events such as Shenhu, Zhuqiong, Nanhai and Dongsha, 4 periods of faults developed in the Fushan and Maichen sags in the southeast of the basin, resulting in 3 dominant fault systems of NE,NEE and NW directions, forming 2 tectonic layers. The faults are of flower, piled flower, petal and bush shapes, forming 4 styles including basal tilted strike-slip, basal stretch Domino, cap extensional detachment and cap sliding traction. The Fushan Sag showed an obvious asymmetric stretching process, forming NE-oriented tectonic transfer zone in the middle. The EW-oriented fault system of stage Ⅳ in the southeast of the basin controlled present oil reservoirs in the 2 sags. The nose-like structural zone in the center and the steep slope step zone in the southeast of the Fushan Sag are favorable petroleum exploration targets in the southeast of the basin.