巴西圣弗朗西斯科盆地石油地质特征

Petroleum Geologic Characteristics of Sao Francisco Basin,Brazil

运用盆地资源评价方法对巴西圣弗朗西斯科盆地的地质背景和石油地质特征进行了系统的分析和研究。结果表明,圣弗朗西斯科盆地形成年代久远,构造演化史复杂,先后经历了断陷期、被动大陆边缘沉积期和前陆沉积期3个构造演化阶段,各阶段的盆地特征存在差异,发育Espinhaco群、Macaubas群以及Bambui群3套主要的充填序列。盆地中有效烃源岩、有利储层和区域盖层均发育于Bambui群和Macaubas群,生储盖配置关系良好。盆内圈闭发育,包括构造圈闭、地层圈闭及构造-地层复合圈闭等多种类型。通过成藏特征分析,认为盆地中的区域不整合面和巴西利亚构造运动所形成的断层和裂缝为油气的运移提供了通道,为油气在不同类型圈闭中的聚集创造了条件。综合各成藏要素,预测盆地西侧巴西利亚构造带周围是可能的油气富集有利区,且油气勘探应以天然气为主。

Both basic and petroleum geology characteristics of Sao Francisco Basin, Brazil are studied and analyzed systematically with basin resource evaluation. According to the research, the basin possesses a long and complicated tectonic evolution history. It underwent the stages of lift, passive continental margin, and foreland in turn. Each stage left its feature in the basin. Three main sequences are formed in the basin： Espinhaco Group, Macaubas Group and Bambui Group. In the basin, effective source rock, favorable reservoir and regional caprock all develope in the Bambui Group and Macaubas Group. Meanwhile, the source-reservoir-cap assemblage in the basin is favorable, and the effective traps are plenteous, including structural traps, stratigraphic traps, and structural-stratigraphic traps. Through the research of accumulation, regional unconformity and fractures formed during Brasilia Orogeny are defined as the migration pathway, which facilitated the accumulation of hydrocarbon in different traps. Moreover, compared with the same kind of basins in the world, the result shows the Sao Francisco Basin possesses favorable petroleum potential.