STRUCTURAL SLOPE-BREAK ZONE: KEY CONCEPT FOR STRATIGRAPHIC SEQUENCE ANALYSIS AND PETROLEUM FORECASTING IN FAULT SUBSIDENCE BASINS
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摘要: 构造坡折带是指由同沉积构造长期活动引起的沉积斜坡明显突变的地带.渤海湾等盆地的研究表明, 断陷湖盆中存在的构造坡折带制约着盆地可容纳空间的变化, 对层序的发育、沉积体系域及砂体的分布起重要的控制作用.在半地堑盆地中可划分出凸起-缓坡边缘、缓坡-洼陷边缘、陡坡-洼陷边缘、凸起-陡坡边缘等断裂坡折带, 识别了“梳状构造”、“帚状构造”、“叉型构造”等同沉积的构造(断裂) 坡折带样式, 它们控制着特定的沉积相域和砂体的展布形式.构造坡折带是油气藏形成的极有利地带.洼陷边缘断裂坡折带, 如“梳状构造”等构成盆地深部预测勘探的重要领域.Abstract: The structural slope-break zone, resulting in the abrupt change of the depositional slope, is initiated by the long-term activity of syndepositional structure. The researches into the Bohaiwan basin indicate that the structural slope-break zone in the fault subsidence lacustrine basin constrained the change in the accommodation space of the basins, controlling the development of the depositional sequence and the distribution of the depositional system tracts and the sand bodies. The half-graben basin may accommodate the following four kinds of structual slope-break zones: uplift-gentle-slope margins, gentle slope-depression margins, steep-slope-depression margins, and uplift-steep-slope margins. Furthermore, several syndepositional structural (fault) slope-break patterns are identified such as "comb-like structure" and "broom-like structure". These structures controlled the distribution patterns of the specific depositional systems tracts and the sand bodies in the basin. The structural slope-break zone is favorable for the formation of petroleum accumulation. The structual slope-break zone at the depression margin such as the "comb-like structure" has proved important for the prediction and exploration of the deep-seated subtle traps in the basin.
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Key words:
- structural slopebreak zone /
- sandbody prediction /
- fault basin
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图 3 横过第三纪渤海湾盆地四扣洼陷的三维地震沉积-构造解译剖面
AF.冲积扇沉积, 楔状发散不连续-较连续反射结构; FD.扇三角洲沉积, 较连续-连续前积反射结构; LST.低位湖底扇-前三角洲浊积, 丘形、叠瓦状、扁透镜状等反射结构; sb3, sb4, sb5分别为沙河街组沙二、沙三和沙四层序的底界
Fig. 3. 3-D seismic profile across the Sikou depression in Bohaiwan basin, showing the relationship between the depositional systems and the syndepositional structures
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