摘要
埕岛东斜坡东营组三段砂体是由水下河道控制的、具有牵引流和浊流双重沉积特征的水下扇。主要发育混杂基质支撑砾质砂岩相、含砾砂岩相、泥质支撑砂岩相和砂质粉砂岩相;粒度粗是其主要特征;粒序层理、块状层理、平行层理、交错层理、波状层理十分发育;滑塌、旋卷、负荷脱水等沉积构造也十分发育;在地震剖面上有明显河道下切现象,呈现顶平底微下凸的宽阔半透镜体;自然电位曲线呈正韵律,曲线由高幅至中幅呈柱状及箱形,与不同岩性和不同沉积相具良好对应关系。根据岩性、电性、物性分析,研究区共识别出水下河道、道间漫溢、道间决口扇、水下天然堤、河道间泥坪、河口朵叶体及席状砂等微相,其中水下河道为主要储集层段。
Abstract
Sand body in the 3rd member of Dongying Fm in eastern slope of Chengdao is controlled by subaqueous channel,with subaqueous fan to be characterized by both traction and turbidity current sediments. The petrographic facies include hybrid matrix-supported gravelly sandstone, pebbled sandstone, argillaceous-supported sandstone and sandy siltstone,which are mainly characterized by coarse-grained sediments. Depositional beddings such as graded bedding,massive bedding,parallel bedding, cross-bedding and wave bedding,are well developed;and depositional structures including slump,convolute and load-dehydration,are also developed very well.Obvious channel downcutting has been recognized in the seismic profiles,which appears as wide semi-lens—being flat on the top and being slightly convex at the bottom;and the spontaneous potential log shows positive rhythm,with columnar and box-like shapes changing respectively from high amplitude to medium amplitude,which are closely related to different lithology and different depositional facies.On the basis of lithology, and electric and reservoir property analyses,depositional facies in this area can be divided into 7 micro-facies,including subaqueous channel,interchannel unconcentrated flow, interchannel splay, subaqueous levee,interchannel mudflat, river mouth lobe and sheet sand microfacies.
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