【摘要】 鄂尔多斯盆地在三叠系延长组沉积时期为大型内陆湖相盆地，沉积了一套北东向的沉积楔形体。根据地震、测井、岩心和露头等资料的综合分析，在延长组中建立了４个可全盆地对比的层序。各个层序的岩相、厚度和分布基本上一致：层序不整合边界上广泛分布粗粒的河道充填沉积物，反映河流通过侧向迁移、侵蚀和沉积作用来适应沉积基准面的下降；在沉积中心，沉积基准面的变化形成了特定的岩相和古生物分布；层序内部序列具有可预测性，低水位体系域由盆地南缘的盆地扇和低水位河道三角洲沉积构成，沉积范围相对较小，上覆的水进体系域则以范围较大的盆地相沉积为特征，高水位体系域由一套前积型三角洲和湖泊相的暗色泥岩夹油页岩组成，伴有大量植物化石。层序地层分析为储层砂体的分析与预测提供了年代地层框架。在盆地中部，层序间高水位与低水位三角洲沉积体的叠合为上覆水进体域的湖相沉积所覆盖，形成了极为有利的地层岩性圈闭。更多还原

【Abstract】 ate Triassic Yanchang Formation in the Eerduosi basin is a depositional wedge with thickness increased towards southwest and decreased towards northeast. Four sequences in the formation are identified by sequence stratigraphic analysis, combined with seismic, well-log, biostratigraphic, and core data. These four sequences are mostly the same in distribution, thickness and facies. The sequence boundaries are the same. In the northern basin, multilateral multistory fluvial channel sandstones overlie sequence boundaries unconformably. It is suggested that fluviation is adjusted by lateral migration, erosion and deposition when accommodation in vertical is limited in lowstand. In the south of basin, change of depositional base level results in specific distribution of sediments and fossil abundance. The depositional succession can be predicted within the sequences: the lowstand system tracts are composed of fine basin fan and lowstand delta deposits in the south of basin, and fluvial channel -fill sediments in the north of basin, and the scale of distribution is limited; the transgressive system tracts are characterized by a series of retrogressional transitional facies in the north of basin, by deep lake deposits such as grey mud and carbonate in the south of basin; the highstand system tracts are composed of suspended - load deposits and progradational detla deposits in the north of basin, and mudstone or carbonaceous shale with a lot of fossils in the south of basin. A chronostratigraphic framework is provided by sequence stratigraphic analysis to analyse and predict the distribution of reservoir sandstones.更多还原