鄂尔多斯盆地三叠纪延长期湖盆底形形态和岩性油藏分布特征

Shape of Lake Basin Bottom and Characteristics of Lithologic Reservoir Distribution in Yanchang Age, Triassic of Ordos Basin

本文从稳定湖泛泥岩厚度印模、层序地层充填形态、沉积微相组合反演古地形以及可容空间（A）和沉积物供给通量（S）之间的关系分析等4个方面，研究了鄂尔多斯盆地三叠纪延长期湖盆底形形态以及湖岸线的变迁演化轨迹。根据延长期湖盆的缓坡边缘（陕北地区）和陡坡边缘（陇东地区）两个基本背景条件以及不同时期、不同位置的沉积地层结构模式、层序充填模式、沉积速率及堆积厚度模式等特征，讨论了湖泊底形与各种沉积响应之间的因果关系，探讨了延长期湖盆底形演化与岩性油藏发育区带之间的必然联系。认为湖盆底形控制着沉积体系的分布格局和储集砂体的散布样式及发育规模。延长期深水湖盆边缘发育的高陡坡度坡折带以及深水地区，是优质岩性油藏密集分布区。

Shape of lake basin bottom as well as the course of vicissitude and evolution of the lake coastlines in Triassic Yanchang Age of Ordos basin are studied in the article, in four aspects of stable lake-flooded mudstone thickness mould method, inverse deduction from sequence stratigraphic firing patterns, paleo-relief inverted from sedimentary micro-facies combination, analysis of relationship between accommodated space （A） and the deposit supplies flux （S）. According to two basic background conditions of Yanchang Age gentle slope edge （the North Shaanxi area） and steep slope edge （east Gansu area）, and sedimentary formation structure pattern, sequence firing pattern, depositing rate and accumulative thickness pattern etc characteristics, in different time and at the different positions, the causal relationship between the lake bottom shape and various depositional responses is discussed, and necessary connection between lake basin bottom shape evolution in Yanchang Age and the lithologic reservoir development zones is also discussed. It is considered that the lake basin bottom shape controls the distribution pattern of sedimentary system and the spreading style and development scale of the reservoir sand bodies. The high steep gradient slope turn zones and deepwater areas developed in edge of deepwater lake basins in the Yanchang Age are densely distributed district of high quality lithologic oil reservoirs.