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南海北部陆坡深水区新生代发育两种类型凹陷:一类为大型继承性断-坳叠合型凹陷,其裂谷期、热沉降期和新构造期沉积都很发育,且在垂向上叠合分布;另一类是断陷型凹陷,主要发育裂谷期沉积。大型继承性断-坳叠合型凹陷中发育3套古近系烃源岩,烃源岩体规模大,以生气为主;主力储层是渐新统滨浅海三角洲砂岩、新近系低位扇砂岩;区域盖层是区域性海相泥岩;凸起及低凸起上披覆构造型圈闭发育,凹陷内凹中隆构造圈闭发育。白云凹陷油气具有垂向运移和辐射状运移双重特征,琼东南盆地深水区具有从烃灶向南汇聚运移的特征。丰富的烃源、高效的输导条件、大量的构造圈闭及其有利的配置关系表明,深水区的大型继承性断-坳叠合型凹陷具有巨大的勘探潜力。相对于大型继承性断-坳叠合型凹陷,断陷型凹陷古近系烃源岩规模小,圈闭类型单一且规模小,其油气勘探潜力还有待进一步证实。
There are two types of diagenesis in the Cenozoic of the continental slope in the northern South China Sea: one is a large inherited fractured-depressed syncove depression, and the sedimentary facies in the rifting, thermal subsidence and neotectonic periods are well developed and vertically superimposed Distribution; the other is a faulted depression, the main development of rifting deposition. There are three sets of Paleogene source rocks in the large successional fault-depression depression depression. The source rocks are large in scale and mainly gas-generating. The main reservoirs are the Oligocene coastal shallow marine delta sandstone, the Neogene lower-fan fanstone ; The regional caprock is a regional marine mudstone; the drape and low protuberances have a drastic trapping of the structural tectono-plastic traps, and the concave Neijiang structural traps develop. The oil and gas in the Baiyun Sag have the dual characteristics of vertical migration and radial migration. The deepwater area in Qiongdongnan Basin has the characteristics of convergence and migration from hydrocarbon stove to the south. The abundant hydrocarbon source, efficient transport conditions, a large number of structural traps and their favorable configuration relationships show that the large-scale succession breccio-sagittal depression in the deepwater area has great exploration potential. Compared with the large successional fault-depression superimposed depressions, the source rocks of the Paleogene source rocks in the depression-depression depression are small in size, single in the trap type and small in scale, and their hydrocarbon exploration potential needs to be further confirmed.