下刚果盆地深水区油气成藏要素特征及成藏模式研究

下刚果盆地是西非被动大陆边缘盆地油气富集区之一,特别在深水区获得了大量的油气发现,逐渐成为盆地油气勘探的热点与重点。盆地深水区油气成藏特征复杂,发育盐上海相、盐下湖相两套烃源岩;发育深层、中层和浅层3套有利储盖组合,目前勘探证实了浅层新近系浊积砂岩和深层阿尔布阶碳酸盐岩储层是盆地的两套主要目的层系,储层物性总体较好,储盖配置关系好;其中浅层组合以构造—岩性圈闭为主,深层组合以近南北向与盐岩相关的构造圈闭为主;各成藏要素在时间、空间上配置关系良好。以成藏要素研究为基础,在下刚果盆地深水区建立了盐上海相烃源生油、新近系浊积砂岩储,盐上海相烃源生油、下白垩统碳酸盐岩储,盐下湖相烃源生油、下白垩统碳酸盐岩储这3种有利的成藏模式。

Hydrocarbon Accumulation Characteristics and Model of Deepwater Zone of Lower Congo Basin

Lower Congo Basin is one of the hydrocarbon abundant margin basins of West Africa passive continent. With a large number ofoil and gas discoveries made particularly in the deepwater zone, the area has become the hot spot for oil and gas exploration. The characteristics of hydrocarbon accumulations in the deepwater zone of the basin are very complicated. Two sets of source rock developed in the area： pre-salt marine and post-salt lacustrine source rock. There are three sets of favorable reservoir-caprock assemblages-deep layer, middle layer and shallow layer. The current exploration has confirmed that the upper Neogene turbidite sandstone and deep Albian carbonate rock reservoirs are the two main targets. Comparatively speaking, the physical properties of reservoirs are good with a desirable matching relation between reservoir and cap-rock. The middle and shallow layer assemblages are mainly the structural-lithological traps while the deep layer assemblage is mainly the near S-N and salt rock-related structural traps. All the elements of the reservoirs are well matched in terms of time and space. Based on the study of the reservoir elements, three favorable accumulations models are established for the post-salt marine source rock and Neogene turbidite sandstone reservoirs, post-salt marine source rock, and Lower Cretaceous carbonate rock reservoirs and pre-salt lacustrine source rock and Lower Cretaceous carbonate rock reservoirs in the deepwater zone of Lower Congo Basin.