摘要： 通过露头剖面研究,能够从二维或三维角度直观地了解沉积实体物质组成、结构构造及岩层间接触关系等地质信息,对于三角洲砂体展布规律预测以及地下储集层地质模型的建立具有重要意义。本文以鄂尔多斯盆地神木地区侏罗系延安组湖相浅水三角洲露头剖面为例,在沉积微相的研究基础上,主要针对水下分流河道、河口砂坝、席状砂等微相,统计单砂体宽度及厚度,分析砂体间接触关系,总结砂体展布规律。研究认为,对于席状砂、水下分流河道两类砂体而言,与湖泊低水位期相比,高水位期砂体宽厚比较大;在湖泊水位一定的条件下,随着距物源变远,A/S值增加,砂体宽厚比增大。受湖泊水位及距物源远近不同A/S值影响,剖面中发育拼接式、切叠式和孤立式3种砂体叠置样式,从拼接式向孤立式A/S值变大,砂体间连通性变差。

关键词: 鄂尔多斯盆地, 浅水三角洲, 湖相, 露头, 水位, 砂体叠置关系

Abstract: Outcrop section study can provide abundant geological information from the perspective of 2D or 3D,such as,sedimentary composition,structure construction and contact relations between strata. And it has a great significance for forecasting delta sandbody distribution rule,as well as the establishment of the underground reservoir geological model. The authors take outcrops of shallow-water lacustrine deltas of the Jurassic Yan'an Formation in Ordos Basin as examples. On the basis of lithofacies and sedimentary microfacies study,statistic analysis of thickness and width of single sandbody was made,and sandbody distribution rule of underwater distributary channel,river mouth and sand sheet was studied. The results show that the sandbody width and thickness ratio of the underwater distributary channel and sand sheet is higher at high water level,compared with that at low water level. Given certain water level,A/S value increases as the distance increases from provenance. Affacted by the A/S value which is controlled by water level and the distance from provenance,there are three main vertical superimposition patterns of sandbodies in subaqueous distributary channel and mouth bar,namely overlay type,joint type and isolated type. From overlay pattern to isolated pattern,the A/S value tend to become higher,and connectivity become lower.

Key words: Ordos Basin, shallow-water delta, lacustrine, outcrop, lake level, superimposed relationship among sandbodies

中图分类号: 

• TE121.3