东海盆地西湖凹陷构造圈闭特征及其油气藏类型

Structural trap characteristics and reservoir types in Xihu Sag, East China Sea Basin

基于三维地震资料连片解释成果,对东海盆地西湖凹陷构造圈闭分布规律、形成时期和成因机制进行系统梳理,并结合油气成藏条件分析得出构造圈闭的主要油气藏类型及特征。研究表明,西湖凹陷主要发育断层型和背斜型两大类构造圈闭,其中断层型圈闭主要分布于西部斜坡带,背斜型圈闭主要分布于中央洼陷反转带。断层型圈闭主要形成于盆地断-拗转换阶段,受控于斜向伸展背景下的断裂组合,定型于始新世末玉泉运动;背斜型圈闭主要形成于盆地拗陷-反转阶段,受花港、龙井运动区域挤压作用控制。西湖凹陷构造圈闭油气藏类型主要有断鼻、断块、断背斜及背斜等,受通源断裂控制各类油气藏具有纵向叠置的特点,导致各区带油气成藏具有“深大浅小、近源近断”特征;中新世末龙井运动期通源活化断裂在控制断层型、背斜型圈闭发育的同时,也决定了各类构造圈闭的油气富集。

3 D seismic data interpretation is systematically carried out by this paper in order to learn the distribution pattern, forming time and genetic mechanisms of the structural traps in the Xihu Sag, East China Sea Basin.Combined with hydrocarbon accumulation conditions, both the main reservoir types and the characteristics of structural traps are revealed. The results show that fault traps and anticline traps dominate the Xihu Sag, among which fault traps are mainly distributed in the slope zone and anticline trap in the inversion zone of the Central Sag. Fault type traps are mainly formed in the rifting stage and controlled by extensional faults and associated structures, while anticline traps mainly formed in the inversion stage controlled by tectonic inversion under a compressional background.The oil and gas reservoirs in the structural traps of the Xihu Sag mainly include the types of faulted nose, faulted block, faulted anticline and anticline. Controlled by source-connected faults, all the oil and gas reservoirs have the characteristics of longitudinal superposition, which resulted in the hydrocarbon accumulations occurred in a pattern with the large in deep, the small in shallow and close to source and fault. In the Late Miocene Longjing movement, the main source faults were reactivated which controlled not only the types of faults and anticlinal traps, but also the accumulation of oil and gas in various structural traps.