南海九龙盆地成藏特征及有利区勘探

Hydrocarbon accumulation characteristics and exploration of the Cuu long basin,south China sea

本文以构造控制沉积,沉积控制成藏为指导开展九龙(Cuu Long)盆地的成藏特征研究,旨在对盆地的有利勘探区进行分析。盆地划分为4个构造演化阶段,即前始新世基底形成期、始新世-渐新世裂谷期、早-中中新世坳陷期、晚中新世-现今热沉降期。在构造演化控制下,盆地主要经历了陆相期、海陆过渡期及海相期三个沉积演化阶段。在构造、沉积作用的影响下,盆地优质的烃源岩主要发育在盆地中部和东部的湖沼相、深海相泥岩沉积,较好的储层主要发育在盆地中部和东部基底裂缝型岩浆岩、三角洲前缘、潮下带砂岩储层中。油气主要赋存在地层上倾歼灭、褶皱顶部中,从晚渐新世开始生成和运移,一直持续至今。盆地I类油气勘探有利区带主要位于储层发育的盆地东部和中部,II类油气勘探有利区带主要位于盆地西部,为盆地下一步勘探目标提供指导。

In this paper, the Cuu long basin were investigated by analyzing the progressive control of tectonic to sedimentary evolution and sedimentary evolution to hydrocarbon accumulation, aiming to assess the favorable area of the basin. The basin was divided into four stages of tectonic evolution, including formation of basement before late Eocene, initial and continued rifting in late Eocene to oligocene, depression stage in early to middle Miocene,thermal subsiding stage in late Miocene to Quaternary, based on the geological structure and history of tectonic evolution of this region. Influenced by tectonic actions, the basin has experienced 3 major sedimentary periods, including terrestrial facies, transitional facies and marine facies. The main source rock is mudstone developed in lagoon and abysmal in middle and east basin, the main reservoir is sandstone developed in delta front and subtidal and magmatic in basement rock. Oil and gas generation and migration has lasted until now since late oligocene. So the most favorable area is located in the middle and east basin, which will provide guidance for further exploration of the Cuu long basin in the next stage.