鄂尔多斯盆地南部上三叠统延长组层序地层格架内沉积相特征与演化*

应用高分辨率层序地层学和沉积学的原理与方法，综合岩心、钻井以及测井和地震资料，对鄂尔多斯盆地南部上三叠统延长组进行了深入的研究，识别出5个层序界面，划分出4个三级层序和11个四级层序，建立了鄂尔多斯盆地南部上三叠统延长组层序地层格架。在研究区识别出曲流河三角洲、辫状河三角洲、深水重力流和湖泊4种沉积相。分析了层序格架内沉积相时空展布特征，揭示了层序格架内沉积相的时空演化规律，归纳了层序格架内砂体发育与展布的特点。讨论了层序界线划分与以往地层界的区别及其实际意义，探讨了重力流沉积对鄂尔多斯盆地油气勘探的重大意义。

Characteristics of sedimentary facies and evolution in sequence stratigraphic framework of the Upper Triassic Yanchang Formation in southern Ordos Basin

According to the theory and approach of high resolution sequence stratigraphy and sedimentology,combining with core,drilling well,well-logging and seisimic data,detailed studies has been carried out on the Upper Triassic Yanchang Formation of the southern Ordos Basin.Totally five sequence boundaries,four 3rd and eleven 4th sequences were identified and the sequence stratigraphy framework was built up.Four types of sedimentary facies were developed in this area,including meandering fluvial delta,braided fluvial delta,lacustrine and deep-water gravity flow facies.The characteristic distribution of sedimentary facies in sequence stratigraphic framework was illustrated,and the law of evolution and distribution of sedimentary facies in sequence stratigraphic framework was established and the distribution of sandbodies in sequence stratigraphy was generalized.Taking the constantly deepening understanding of the sedimentary facies as the guidance,great breakthrough has been made in the petroleum exploration of the Yanchang Formation in the Ordos Basin.