Southwest Ordos Basin has become a popular target in petroleum exploration and production, recently, which has plenty of petroleum resources, so a clear understanding of rules of basin bottom morphology is of great significance in petroleum exploration. A study of stacking style of sandstones and migrating rules of deep lake region, together with, many event depositions show that the center of basin migrated from northeast to southwest along with frequency earthquakes, lava, source uplift and front subside caused by Qinling orogenesis in period of Chang 7 Formation deposition. So, braided delta and turbidite formed in southwest basin because of asymmetrical basin in which the south is steep and the north is slow. Basin bottom configuration changes from symmetrical to asymmetrical, and sedimentary facies changes from meandering delta to braided delta. At the same time, turbidite, tuff and sand dike are formed by Qinling orogenesis. Based on the evolution history of the lake basin bottom, the turbidite in Huachi, Qinchen and Zhenning area will be a potential petroleum exploring target.%鄂尔多斯盆地西南缘延长组具有非常丰富的油气资源,是近年来增储上产的主要领域,明确盆地底形的演化规律对今后的油气勘探具有非常重要的意义.通过对主要目的层的砂体堆砌样式、半深湖深湖区的迁移规律研究,结合盆地大量存在的事件沉积,表明:上三叠统长7期是盆地西南缘秦岭造山最活跃的时期,地震频繁、火山喷发、物源区发生隆升,造山带前缘快速下沉,湖盆中心迅速向西南缘迁移,南陡北缓的不对称湖盆形成.湖盆底形由对称变为不对称、沉积相由曲流河三角洲转变为辫状河三角洲,浊积岩、凝灰岩、砂岩脉的形成均与秦岭造山有密切关系.根据湖盆底形的演化规律,认为盆地西南缘的华池—庆城—正宁地区长7段浊积岩砂体具有良好的油气勘探前景.
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