南海南部大陆边缘两个盆地带油气地质特征

Petroleum geological characteristics of two basin belts in southern continental margin in South China Sea

基于地震、钻井、岩心和露头等资料,系统分析南海南部各盆地成盆、成烃、成藏特征,揭示南海南部陆缘盆地油气地质特征,总结油气地质分布规律。研究表明,南海经历古南海形成与发展、古南海消减与新南海发展、南海快速沉降与萎缩等3个构造阶段,古、新南海的构造演化控制了南海南部大陆边缘的区域构造格局,形成南、北两个盆地带,并控制了各盆地带成盆、成烃和成藏特征。南盆地带烃源岩以中新统煤系烃源岩为主,热演化程度不均,近岸生油远岸生气,挤压褶皱构造带和生物礁群是有利区带。北盆地带烃源岩以始新统—渐新统为主,热演化程度高,以生气为主,生物礁、断块为其主要聚集区。研究认为,南海南部大陆边缘盆地尚有很大勘探潜力,是油气勘探开发的重要领域,南盆地带应油气兼探,北盆地带以找气为主。

Based on the seismic, drilling, cores and outcrops data, the formation of basins, source rocks and hydrocarbon accumulations in the southern South China Sea（SSCS） were systematically analyzed to reveal the petroleum geological features of continental margin basins and summarize the distribution rule of oil and gas in the SSCS. The results show that the South China Sea（SCS） has experienced three tectonic stages, namely, the formation and development of pro-SCS, the subduction of pro-SCS and development of neo-SCS, the rapid subsidence and shrinking of SCS. The tectonic evolution of pro-SCS and neo-SCS controlled the regional tectonic pattern of continental margin in the SSCS, forming southern and northern basin belts, and also dominated the formation of basins, source rocks and hydrocarbon accumulation characteristics. The source rocks were mainly Miocene coal source rocks in the southern basin belt, with different thermal evolution degree, and the near-shore source rock was chiefly oil-generating while the off-shore source rock was mainly gas-generating. Compressive folding structural belts and reefs were the favorable belts. Within the northern basin belt, the source rocks were gas-prone and dominated by the Eocene to Oligocene, with high thermal evolution degree. Reefs and faulted blocks were the major accumulation areas. Our study demonstrates that the continental marginal basins of SSCS still have great exploration potential and is an important strategic area of oil and gas exploration and development. The southern basin belt focuses on oil and gas exploration and the northern basin belt focuses on gas exploration.