陆相湖盆扇三角洲-滩坝体系砂体展布特征与叠置模式——以渤海湾盆地饶阳凹陷留西地区沙三上亚段为例

基于高分辨率层序地层学理论,综合利用岩心、测录井、地震及实验室分析化验资料,识别了断陷盆地陡坡带扇三角洲-滩坝体系的沉积特征,探讨了砂体展布的控制因素,最后建立了留西地区沙三上亚段砂体的叠置模式。研究表明:①水下分流河道、河口砂坝和滩坝砂体为研究区主要的砂体类型。②顺物源方向,受地形变缓影响,扇三角洲水下分流河道的宽度与深度逐渐减小;高频(四级)湖平面的变化控制了扇三角洲-滩坝体系的进积与退积,更高频次(五级-六级)湖平面的变化控制了层序内部砂体的叠置样式与展布规律。③研究区不同类型的砂体垂向叠置模式主要有4种,分别为深切河道叠置、坝上河叠置、孤立河道叠置及河口砂坝-滩坝复合叠置。

Distribution characteristics and stacking patterns of sandbodies in the continental lacustrine fan delta-beach dam system:A case study from submember 3 upper of Paleogene Shahejie Formation in Liuxi area,Raoyang Sag,Bohai Bay Basin

Based on the high resolution sequence stratigraphy theory,the sedimentary characteristics of the fan delta-beach dam system in the steep slope of the fault depression basin are identified by the comprehensive application of the core,logging,seismic and laboratory data. It discussed the controlling factors of the distribution of sand bodies in this area,and established the superposition model of sand bodies in the submember 3 upper of Shahejie Formation in Liuxi area. The results show that :(1)Underwater distributary channel,river mouse bar and beach bar sand bodies are the main sand bodies in the study area.(2)In the direction of the source,the width and depth of the underwater distributary channel in the fan delta are gradually reduced due to the slow topography. The variation of high frequency(level 4)lake level controls the progressive and regressive deposition of the fan delta and beach dam system,and the variation of higher frequency(level 5-6)lake level controls the superposition style and distribution rules of sand bodies in the sequence.(3)There are four types of vertical superposition modes of sand bodies in the study area,which are deep water channel superposition,river over bar superposition,isolated river superposition and river mouse bar-beach dam composite superposition.