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三叠系延长组是鄂尔多斯盆地中生界重要的含油气层位,属典型的岩性油藏,具有含油层位多、成藏关系复杂的特点,其中烃源岩发育特征对岩性油藏分布具有重要的控制作用.基于露头和测井资料,将鄂尔多斯盆地南部延长组自下而上划分为SQ1、SQ2和SQ3三个三级层序,研究了层序地层格架控制下烃源岩的发育特征及其控制因素.研究结果表明:主力烃源岩赋存于湖侵体系域,以长7段为代表,属湖泊扩张至最大湖泛期物源补给欠补偿时半深湖-深湖相沉积,缺乏大量陆源碎屑注入而发育腐泥组占绝对优势的高有机质丰度烃源岩.高位体系域亦发育有烃源岩,如长9段和长6-4+5段,属最大湖泛期后物源补给超过基准面上升而向湖盆推进的滨湖相、浅湖相沉积,陆源碎屑输入致其表现为腐植型占优势且具较高有机质丰度的烃源岩.油源对比显示延长组油源主要来自晚三叠世延长组最大湖泛期形成的长7段湖侵体系域,说明不同体系域烃源岩对延长组油藏的贡献存在差异.层序地层沉积动力背景下体系域可容纳空间垂向与侧向变化,不仅决定体系域内部沉积相类型展布,更直接控制体系域内烃源岩有机质丰度和类型.研究层序地层格架中不同体系域内烃源岩赋存的差异性,有助于在层序沉积背景下预测和评价盆地内烃源岩分布规律.
The Triassic Yanchang Formation is an important petroleum reservoir in the Mesozoic in the Ordos Basin. It is a typical lithologic reservoir with many oil-bearing beds and complex reservoirs. The characteristics of hydrocarbon source rocks are of great significance to lithologic reservoirs Distribution is of great importance.According to outcrop and well logging data, the Yanchang Formation in the southern part of Ordos Basin is divided into three third-order sequences SQ1, SQ2 and SQ3 from bottom to top, and the source rocks And its controlling factors.The results show that the main source rocks occur in the lacustrine system tract and are represented by Chang 7 Member, belonging to the semi-deep lake-deep Lacustrine facies, the lack of a large number of terrigenous clastic intrusion and the development of sapropel group of absolute advantage of high organic matter abundance source rock .High system tract also developed source rocks, such as Chang 9 and 6-4 + 5, Which belongs to the hydrocarbon source with dominant humic type and high organic matter abundance due to the input of terrestrial sources beyond the datum and advanced to the lacustrine basin after the maximum lagoon flood period The correlation between oil source and source indicates that the source of Yanchang Formation mainly comes from the extension of Late Triassic The results show that there are differences in the contribution of different system source rocks to the Yanchang Formation reservoirs.According to the sedimentary motivation of sequence stratigraphy, the system domain can accommodate vertical and lateral changes of space, Not only decides the distribution of sedimentary facies in the system tract but also directly controls the abundance and type of organic matter in source rocks in the system tract.The study of the differences in the occurrence of source rocks in different system domains in the sequence stratigraphic framework contributes to Predict and evaluate the distribution of source rocks in the basin under sedimentary background.