莺歌海盆地中央底辟带油气成藏条件分析

ANALYSIS ON HYDROCARBON POOL-FORMING CONDITION OF CENTRAL DIAPIRIC ZONE IN YINGGEHAI SEA BASIN

宫少波 王彦

Gong Shaobo Wang Yan

莺歌海盆地位于海南岛以西、中南半岛以东的海域,总体呈NW-SE向。该盆地由中央底辟带和斜坡带两个构造单元组成。底辟带发育中新统(莺黄组、梅山组和三亚组)及渐新统(崖城组)两套烃源岩,生油门限深度在2800～3000m之间;主要圈闭由底辟流体上拱形成,底辟活动的幕式发育决定了油气幕式运移。不同的油气运移动力形成了不同类型的油气藏:中新统源岩在高温高压及欠压实作用下,形成高压囊,使上覆地层破裂,产生高角度断层和裂隙,烃类气沿此形成深部及浅部气藏;另外,本区深部的无机成因CO气在高压作用下,排驱断裂附近的烃类气,一方面对原有气藏进行破坏,另一方面在远离断裂的两翼形成含少量CO气体的新的烃类气藏。

Yinggehai Sea Basin is situated in the west of Hainan Island and the east of Zhongnan Peninsula and stretches in NW-SE direction.The basin consists of central diapiric zone and a slope zone.Two sets of source rocks including Miocene Yinggehai,Huangliu,Meishan and Sanya Formations and Oligocene Yacheng Formation developed in the diapiric zone.Oil threshold is between 2 800～3 000 m depth.The traps were formed by the upward arch of diapiric fluid,and episodic diapir activity determined hydrocarbon episodic migration.Different migration dynamic forces resulted in different types of oil and gas pools:under high temperature,high pressure and uncompaction,the Miocene source rocks formed high pressure pocket which break overlying strata and formed deep and shallow gas pools;deep seated inorganic CO under high pressure expelled the hydrocarbon gas near fractures,destoried the original gas pools and formed new hydrocarbon gas pools with little Co.

10.11743/ogg20000309