运用高分辨率层序地层学的方法, 在充分收集、整理测井、地震及钻井资料的基础上,深入研究陕西富县上三叠统延长组长8段的高分辨率层序地层学特征.将长8划分为1个长期、2个中期(MSC1和MSC2)和若干个短期基准面旋回,编制了2个中期基准面旋回的岩相古地理图.结果表明:MSC1期为湖盆扩张期,以发育退积型浅水三角洲和湖底扇为特征,MSC2期为湖盆稳定充填期,以加积型三角洲为特征,湖底扇萎缩;长8段主要发育A2型、C1型、C2型和C3型四种短期基准面旋回模式,砂体成因种类和基准面架构具备从目标区的NE至SW由内三角洲前缘A2型→外三角洲前缘C1型→外三角洲前缘C3型→半深湖C2型或湖底扇A2型的分布规律;最有利的储集砂体成因类型为A2型水下分流河道砂体和A2型湖底扇砂体;且顺物源方向的空间连通性好,有利于发育岩性圈闭,是研究区的重要勘探目标.%Based on the core,logging and seismic data, the high-resolution sequence stratigraphy of member Chang-8 of Yanchang Formation, Fuxian area in Ordos basin, was studied.Member Chang-8 is divided into one long-term,two medium-term cyclic sequences (MSC1,MSC2) and several thort-term cyclic sequences, and two maps about medium-term cyclic Sequence-based lithofacies & paleogeography was constructed.Then conclusion that MSC1 is the expansion period of Ordos lake basin, when retrogradation shallow water delta and sublacustrine fan developed, MSC1 is the stability period, aggradational shallow water delta developed and sublacustrine fan withered.There are four types of thort-term cyclic sequences,i.e.typeA1,typeC1,typeC2 and typeC3, which form the northeast to southwest, the distribution model of the base-level cycle type and sandbody′s genetic type is typeA2(inside delta front)→typeC1(outside delta front)→typeC3(outside delta front)→typeC2(deep lake) or typeA2(sublacustrine fan).The best favorable sandy reservoir is typeA2 formed by underwater distributary channel and sublacustrine fan, which is of good interconnectedness along provenance direction,and is the significant exploration target.
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