论文部分内容阅读
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。
The Ordos Basin was a large inland lacustrine basin deposited during the Triassic Yanchang Formation and a northeastern depositional wedge was deposited. Based on the comprehensive analysis of the data of seismic, well logging, core and outcrop, four sequences that can be compared in the whole basin are established in the extension group. The lithofacies, thicknesses and distributions of each sequence are basically the same: the coarse-grained channel-filled sediments on the unconformity boundaries of the sequences reflect that the rivers adapt to the decline of sedimentary datum by lateral migration, erosion and sedimentation; Sedimentary center and sedimentary datum change resulted in the formation of specific lithofacies and palaeontological distribution. The sequences within the sequence are predictable. The lowstand system tract consists of basin fan and low-water delta deposits in the southern margin of the basin, Small, overlying waters are characterized by the deposition of a large range of basin facies, which consists of a set of dark muddy-clastic, oil-bearing shales of pre-sedimentary delta and lacustrine facies with abundant plant fossils. Sequence stratigraphic analysis provides a stratigraphic framework for the analysis and prediction of reservoir sand bodies. In the central part of the basin, the superimposition of sedimentary bodies of high and low water level delta beds in the basin is covered by lacustrine sediments in the overlying water-body domain, forming an extremely favorable stratigraphic lithologic trap.