巴西坎波斯(Campos)盆地石油地质特征与勘探有利区分析

Petroleum Geology and Analysis on Favorable Exploration Targets of Campos Basin,Brazil

巴西坎波斯(Campos)盆地是南美洲大陆东缘的一个典型大西洋型被动大陆边缘型盆地。盆地经历了前裂谷→同裂谷→过渡→后裂谷(漂移)等4个演化阶段。盆地裂谷期发育的Lagoa Feia湖相黑色页岩为盆地主要的烃源岩,在始新世(52Ma)时达到生油窗开始生油,在中新世(22～8Ma)达到生油高峰。盆地主要发育上白垩统和第三系Carapebus浊积砂岩、下白垩统Macae组碳酸盐岩和Lagoa Feia组鲕粒灰岩以及前寒武系的Cabiunas组裂缝玄武岩等4套储集层。盆地过渡期发育的Alagoas组盐岩层是盆地良好的区域性盖层,第三系层间泥页岩为盆地局部层间盖层。以主要含油气储集层为核心,盆地可以划分出下部、中下部、中上部和上部等4套主要的油气成藏组合,其中上部Carapebus浊积砂岩体成藏组合内已发现的可采储量占盆地总可采储量的80%以上,是盆地最重要的成藏组合。未来盆地最具潜力的勘探领域为Campos断层以东的Carapebus成藏组合的浊积砂岩体和Lagoa Feia成藏组合渗透性的鲕粒灰岩。

The Campos basin at the east margin of South America is a typical passive margin basin of the Atlantic type.Campos Basin went through four evolution phases： Pre-rift、Syn-rift、Transitional and Post-rift.The Lower Cretaceous lacustrine black shales of the Lagoa Feia formation formed in the syn-rift phase is the primary source rocks,which started to generate oil at Eocene（52 Ma） and reached its oil generation peak during the Miocene（22-8 Ma）.The Upper Cretaceous and Tertiary turbidities,Lower Cretaceous carbonate of the Macae formation,oolitic grainstones of the Lagoa Feia formation and the fractured basement of Cabiunas formation are the four main reservoirs developed in the basin.The evaporate rock of the Alagoas formation of the transitional phase provides a regional seal for the underlying reservoirs and the Tertiary intra-formational marine shale provides a local seal.There are four main reservoir assemblages developed in the basin and the upper turbidities assemblage of the Carapebus formation is the most important one,which takes about 80% of the total recoverable reserves of the basin.Two potential exploration targets in the basin are： the turbidities of the Carapebus assemblage and oolitic grainstones of the Lagoa Feia assemblage.