巴西深水盆地对比及油气成藏规律分析

对巴西东部被动大陆边缘深水盆地群的构造演化和石油地质特征进行了系统性的对比分析,研究表明,盆地群经历了4个演化阶段:前裂谷阶段、同裂谷阶段、局限海过渡阶段和被动大陆边缘漂移阶段。受区域构造应力场、膏盐层、火山岩等方面的影响,各盆地表现出不同的盆地结构和构造样式,而膏盐层的发育对于油气成藏起着关键作用。这些盆地中,主要发育了三套烃源岩、三套储层和三套区域盖层,并形成了三种油气成藏类型:盐下裂谷地堑内的构造油气藏,膏盐层上下的碳酸盐岩油气藏,以及盐上的浊积岩构造—地层复合油气藏。根据成藏规律分析,并考虑各盆地的勘探现状,按勘探潜力由好到差的顺序将盆地划分为三类,指出Ⅰ、Ⅱ类潜力区应是主要勘探方向,具有广阔的油气资源前景。

Comparison of Petroleum Geology Characteristics and Hydrocarbon Accumulation Regularity of Deep Water Basins in Eastern Part of Brazil

Based on systematic analysis of tectonic evolution and petroleum geology characteristics of deep water basins in the eastern part of Brazil, it is shown that these basins developed in passive continental margin mainly have gone through four evolution stages, i.e., the pre-rifting, the syn-rifting, the restricted-sea transitional and the post-rifting stages. Due to influences of regional tectonic stress fields, salt beds and volcanism, different one in the basin group plays its own basinal structures and tectonic style, and the salt beds play a pivotal role in hydrocarbon accumulation. Three sets of source rocks, three sets of reservoir and three sets of regional cap rocks develop respectively in al of marginal basins and thus three types of hydrocarbon reservoirs are comprised: (1) pre-salt rifting structural reservoirs, (2) post-salt or pre-salt carbonate reser-voirs and (3) post-salt turbidite structural-stratigraphic reservoirs. On the basis of the analysis of hydrocarbon accumulation regularity and taking account of exploration practice in every basin, these deep water marginal basins can be divided into three grades of exploration potential, the good (GradeⅠ), the common (GradeⅡ) and the poor (Grade Ⅲ) one. It is sug-gested that the GradesⅠandⅡof potential areas should be prospective.