鄂尔多斯盆地东南部山西组沉积特征

Sedimentary characteristics of early Permian Shanxi formation,southeastern of Ordos basin

根据薄片观察及粒度分析、野外露头及岩心观察,分析鄂尔多斯盆地东南部山西组的岩石学特征、水动力条件,以及宏观和微观沉积特征,划分岩相类型和岩相组合,建立该区三角洲前缘沉积模式。结果表明:鄂尔多斯盆地东南部山西组沉积粒度偏细,分选好,水动力条件以牵引流为主;三角洲前缘沉积特征明显,且沉积地形坡度较缓;划分7种岩相类型和3种岩相序列组合。研究区整体表现为三角洲前缘沉积特征,主要发育水下分流河道、水下分流间湾、分流河口砂坝3种微相。该结果为鄂尔多斯盆地东南部山西组天然气精细勘探开发提供参考。

In order to study the sedimentary characteristics of Shanxi formation in southeastern of Ordos basin,based on the analysis of thin sections and grain size,observing of outcrops,detailed description of the cores,we analyzed petrological feature and hydrodynamic condition,dissected macro and micro sedimentary feature of Shanxi formation,and lithofacies and its assemblages had been divided.The results showed that the sedimentary characteristics of Shanxi formation can be summarized into:Fine-grained,well-sorted and hydrodynamic dominated by traction flows.Obvious typical features of delta-front with a gentle slope depositional topography.Lithofacies was divided into 3kinds of combinations with 7types.The sedimentary characteristics manifest delta front figures in general,it mainly developed three microfacies:Subaqueous distributary channel,subaqueous inter-distributary bay and distributary mouth bar.Finally,sedimentary model was established after the detailed analysis of the sedimentary characteristics of the Shanxi formation,which can provide guidance for the natural gas delicate exploration of the Shanxi formation in southeastern of Ordos basin.