南海珠江口盆地走滑构造与油气成藏机制

Relationship Between Strike-slip Structure and Hydrocarbon Accumulation in the Pearl River Mouth Basin in the Northern South China Sea

受南海海盆演化以及邻区构造事件的联合控制,南海北部珠江口盆地内部构造表现出明显的多期走滑特征。走滑拉分作用控制了珠江口盆地现今的构造格局,在区域地质构造研究的基础上,本文通过重磁资料,在区域内共识别出NW和NE两组走滑断层,并根据阳江东凹最新三维地震资料的精细解析,识别出花状构造、雁列式和羽状等多种具显著走滑特征的构造样式,进而研究了各期走滑构造对成盆的控制作用,分析走滑拉分盆地的沉积充填特征及对油气成藏的作用。研究结果表明:盆地走滑构造对油气成藏分布有明显的控制作用,对烃源岩热演化、构造圈闭发育以及油气运移聚集都有重要的控制作用,进而讨论了珠江口盆地走滑构造对油气的富集规律与分布的影响作用,对该盆地的勘探实践具有重要指导意义。

The Pearl River Mouth Basin in the northern South China Sea continental margin is a pull-apart basin controlled by strike-slip faulting as a response of the spreading of the South China Sea Ocean Basin and tectonics in its adjacent areas.Two sets of strike-slip faults,striking NW and NE,respectively,have been identified in the study area based on the gravity and magnetic data.The precise interpretation of seismic profiles reveal that there are various structural styles with distinct strike-slip features in different periods,such as flower-like,house tail-like and plume-like structures.The effects of the strike-slip faulting on basin formation and the sedimentary filling and its effect on hydrocarbon accumulation are discussed base on case study of the eastern Yangjiang Sag.The results show that the strike-slip feature of the internal structure in the basin has a significant control on the thermal evolution of the source rocks,the development of structural traps,and the migration and accumulation of oil and gas.The strike-slip faulting forms three types of oil and gas accumulation models,three-dimensional migration and accumulation,migration and accumulation due to compression and distortion along the fault strikes,and near-sag-source migration and accumulation.We suggest that the strike-slip structure controls the accumulation and distribution of oil and gas in the Pearl River Mouth Basin and is critical for oil and gas exploration.