鄂尔多斯盆地晚三叠世延长组湖盆演化及石油聚集规律

延长组湖岸线、深湖线及湖盆底形恢复显示,延长组湖盆具有向西南部迁移,再向东北部迁移的演化特点。长6期湖盆底形具有"南陡北缓、西陡东缓"的特点,盆地中心位于庙湾以北、正宁以东、甘泉以南地带,造成盆地东北部为缓坡型三角洲体系,而西南部为陡坡型辫状河三角洲,前缘末端发育浊积扇。延长组划分为5个三级层序,控制了4套生储盖的分布。延长组湖盆演化与石油的聚集关系密切,湖岸线附近的三角洲前缘是油气的主要富集区,深湖区的浊积砂体也具有一定的储集性能和良好的成藏条件。东北部、西南部主要成藏组合及深湖浊积岩的特征表明,可以进一步向盆地腹地扩大勘探。

Lake basin evolution and petroleum accumulation of Late Triassic Yanchang Formation in Ordos Basin

The lakeshore line,deep lake line and bottom configuration restoration of lake basin in Yanchang Formation show the evolvement characteristics of lake basin migrating to the southwest and then to the northeast. The lake basin of the Member Change 6 is characterized by steeping in south and west,and slowing in north and east. The center of basin locates in the north of Miaowan,the east of Zhengning and the south of Ganquan,which leads to gentle slope delta system in northeast,abrupt slope braided-delta in southwest,and turbidite fan in front end of braided-delta. Yanchang Formation can be divided into five sequences in third-level and controlled the distribution of four source-reservoir-cap units. Lake basin evolution of Yanchang Formation shows intimate accumulation with petroleum,and the delta front near lakeshore line is the main petroleum abundance zone,while the turbidite sandbody in deep lake also has certain reservoir capability and good accumulation condition. The characteristics of main accumulation combination and turbidite in deep lake in northeast and southwest show the possibility of further exploration forward basin hinterland.