“构造坡折带”——断陷盆地层序分析和油气预测的重要概念

STRUCTURAL SLOPE-BREAK ZONE: KEY CONCEPT FOR STRATIGRAPHIC SEQUENCE ANALYSIS AND PETROLEUM FORECASTING IN FAULT SUBSIDENCE BASINS

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 .

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.