典型大西洋型深水盆地油气地质特征及勘探潜力:以巴西桑托斯盆地为例

Petroleum geology and favorable exploration potential of typical South Atlantic deep water basin: Taking Brazil Santos Basin as an example

巴西桑托斯(Santos)盆地是典型的大西洋型深水盆地:盆地经历同裂谷→过渡→后裂谷(漂移)3个演化阶段。裂谷期Guaratiba组湖相黑色页岩为盆地主要的烃源岩,后裂谷期Itajai-Acu组深水页岩是盆地次要的烃源岩;盆地主要发育第三系Marambaia组浊积砂岩、白垩统Santos组浊积砂岩、Guaruja组碳酸盐岩和Guaratiba组砂岩和灰岩共4套储集层,油气主要富集在Guaratiba组砂岩和灰岩储集层中;盆地过渡期发育的Ariri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,将盆地划分为下部、中部和上部3套成藏组合,运用油藏规模序列法预测3套成藏组合待发现可采资源量分别为17.673×109,14.138×109和6.821×109桶,综合分析认为盆地下部勘探潜力区为东部的下部成藏组合和西部的中、上部成藏组合。

The Santos Basin is a typical South Atlantic deep water basin which went through three evolution phases,i.e.： syn-rift,transitional and post-rift.The lower Cretaceous lacustrine black shale of the Guaratiba formation which formed in the phase of syn-rift basin is the primary source rock,and the post-rift Itajai-Acu deep water shale is the minor source rock.The Tertiary Marambaia turbidities,Cretaceous Santos turbidities,Guaruja Carbonates and Guaratiba sandstone and limestone are major reservoirs,hydrocarbon mainly accumulates in Guaratiba reservoir.The Ariri salt developed in transitional stage is regional seal,and the tertiary interlayer mudstone and shale could be local seal.Santos Basin could be divided into three plays cored on major hydrocarbon bearing reservoir,which are upper play,middle play and lower play. The undiscovered recoverable resource of lower,middle and upper plays have been calculated by using reservoir size sequence method are 17.673×109,14.138×10 9and 6.821×10 9barrel,respectively.The most favorable exploration targets are the lower syn-rift turbidities under thick salt layer in eastern deep water zone and upper and middle plays in thin and transitional zone.