南大西洋两岸被动大陆边缘盆地油气地质特征对比

通过对南大西洋两岸被动陆缘盆地构造演化、地层发育、成藏要素以及盆地勘探数据的对比分析,总结了两个地区的石油地质条件及油气分布差异,并初步探讨了其成因。西非被动陆缘盆地油气资源量远大于南美东部被动陆缘盆地,前者油气主要赋存于盐上层序,以构造、构造-地层圈闭为主;后者以盐上层序为主,盐下次之,构造-地层圈闭居多。两岸被动陆缘发育的宽窄程度不同,西非大陆边缘宽、窄相间发育;南美东部则具中、南部宽北部窄的特点。总体上,西非沿岸盆地烃源岩品质及成熟度要优于南美东部沿岸盆地,且前者盐上多发育深水浊积砂体,油气运移主要受断裂的控制,以垂向穿层(盐岩)运移为主;而后者盐下碳酸盐岩储集层可能广泛分布,油气运移兼有垂向和侧向运移,油气运移受断裂、不整合和岩性多种因素共同控制。

Comparison of Hydrocarbon Geological Characteristics of Intercoastal Passive Continental Margin Basins,South Atlantic Ocean

By comparing the tectonic evolution,stratigraphic development,petroleum accumulation elements and exploration data in intercoastal passive continental margin basins in the south Atlantic ocean,this paper summarized the petroleum geological conditions and hydrocarbon distribution discrepancies of the two regions,including the genesis of their formations.The passive continental margin basins of West Africa have much more petroleum resources than those of eastern South America.The former’s hydrocarbons are mainly found in post-salt sequences,dominant in structural and structural-stratigraphic traps,whereas the latter’s hydrocarbons are found priority to post-salt sequences,secondary to pre-salt sequences,dominated by structural-stratigraphic traps.The development of continental margins is different in width and narrow extent,the West Africa is in alternately development,while the eastern South America is of nature of wide mid-south part and narrow north part.In general,the former has better quality and maturity of source rocks than the latter’s,with well developed post-salt deep water turbidite sandstone and fault controlled petroleum vertical migration style of West Africa basins,compared with the broadly developed pre-salt carbonate reservoir and petroleum vertical and lateral migration controlled by fault,unconformity and lithology of eastern South America basins.