苏丹Muglad盆地Nugara凹陷AG组层序地层及地震相研究

Study on the Sequence Stratigrahy and Seismic Facies of the Abu Gabra Formation in Nugara Depression,Muglad Basin,Sudan

基于地震、钻井及录井资料分析,将苏丹Muglad盆地Nugara凹陷AG组整体作为一个二级层序,内部划分出五个三级层序,自下而上依次命名为SQA^SQE,各层序边界在地震和钻测井资料上特征明显,且对应良好。在建立的层序地层格架内,通过识别不同地震反射单元的外部形态、内部结构、振幅、连续性和频率,在AG组内部五个三级层序内识别出席状平行—亚平行相、楔状相、前积相、丘状相、杂乱相等地震相类型,地震相类型在各个层序中的发育分布具有继承性及连续性,以此建立地震相演化模型。根据地震相展布特征,结合岩心相和测井相分析与标定,认为AG组主要发育三角洲、辫状河三角洲、扇三角洲、冲积扇及湖泊五种沉积相类型,同时讨论了地震-沉积相演化规律及受控因素。

Based on integrated analysis of seismic and well logging data, the AG Formation, a supersequence, in the Nugara Depression of Muglad Basin of Sudan can be subdivided into five 3rd order sequences named SQA^SQE from the bottom to the top. The characteristics of each sequence boundary are clearly shown in both seismic profiles and well logs. In the sequence stratigraphic framework, according to the internal reflection textures and external geometric configurations and in combination with characteristics of seismic amplitude, continuity and frequency, five seismic facies are identified in the AG Formation including parallel-subparallel sheet, wedge shaped, foreset, moundy and unorganized seismic facies. These seismic facies can help build the evolution model of sedimentary facies because these facies should be continuous and can be inherited. The normal delta, braided delta, fan delta, lacustrine system and alluvial fan can be recognized based on seismic data, well data as well as cores. The seismic-sedimentary facies evolution and its controlling factors are also analyzed in this paper.