东非Anza盆地结构及沉积充填演化

Structure and sedimentary-filling evolution of Anza Basin of East Africa

通过对Anza盆地的地震、钻井及周边野外地质资料的综合分析,较为详尽地阐述了Anza盆地的区域地质特征和盆地结构,确定了Anza裂谷盆地的叠合改造性质。重点分析了Anza盆地自Karoo期以来的构造、沉积演化特征,认为盆地的主要经历了Karoo期裂陷、白垩纪-古近纪裂陷及新近纪坳陷沉积,形成了明显的下部断陷、上部广覆式坳陷的双层沉积充填结构。盆地湖相地层主要发育在早白垩世的快速裂陷阶段,并到早白垩世晚期快速消亡,后期几乎全是河流相的粗碎屑沉积,在裂谷活动中缺乏旋回性湖相地层的发育过程。这种演化发育的特点决定了Anza盆地下白垩统发育的三角洲前缘沉积是油气勘探比较有利的储集相带,发育较好的储盖组合。

Through analyzing the seismic data,wells data and filed samples data of Anza basin,the regional geological characteristics and configuration of the basin were expatiated,and the overlap characteristics of Anza rift basin were confirmed.Based mainly on analysis of the processes of tectonic and sedimentary evolution of Anza Basin after Karoo stage,Anza Basin was divided into Karoo rifting,Cretaceous-Paleogene rifting and Neogene riffing,and formed the two types filling styles such as the lower fault depression and upper extensive subsidence.The lacustrine facies sediment mainly developed in rapidly rifting stage of early Cretaceous,and died out in later stage of early Cretaceous,the strata above the Lower Cretaceous are fluvial coarse grain sediment.This basin is a typical over compensating and quickly filling sedimentary basin.It is lack of cyclicity of the lacustrine strata from the rift stage of early,developed to die out in Early Cretaceous.The evolution characteristics of Anza Basin decided that the delta front is favorite reservoir formation in Lower Cretaceous in this basin.