通过鄂尔多斯盆地南部中生界延长组层序地层分析，将延长组划分为5个长期旋回，22个中期旋回 在层序地层格架控制下，研究了鄂尔多斯盆地南部沉积体系及其砂体展布特征。研究区发育北东、南西2大物源体系，其中北东物源(强势物源)，为曲流河三角洲沉积体系，提供了富县一旬邑一宜君地区的沉积。发育2～3支分流河道砂体；南西物源为辫状河三角洲沉积体系，提供了陇东地区和镇泾地区沉积，发育4～5支分支河道砂体，纵向上具有良好的继承性。西南部砂体主要发育于长8油层组，东北部砂体主要发育于长6、长2+3油层组．东南部水下分流河道砂体与低幅度构造的组合区成为油气的有利聚集区。

Based on the analysis of hish resolution sequence stratigraphy of Yanchang Formation in southern Ordos Basin，Yanchang Form ation is divided into five long-term cycles and 22 mid-term cycles．The sedimentary system and sand body distribution are studied．There are two provenance systems developed in the northeast and southwest of the study area．The meandering river delta in the northeast deposited in Fuxian-Xunyi-Yijun area，and developed two to three distributary channels．The braided delta in the southwest mainly deposited in Longdong and Zhenjing area,and developed four to five branch channel sand bodies with favorable inherit．The sand bodies in the southwest mainly developed in Chang 8 reservoir，while the sand bodies in the northeast mainly developed in Chang 6 and Chang 2+3 reservoirs．The subaqueous distributary chan nel san d bodies and low—amplitude structures in the southeast are the favorable zones for oil and gas accumulation．