陕北地区上三叠统延长组三角洲骨架砂体粒度特征

大型湖盆三角洲砂体是中国陆相盆地最重要的油气储集层，进行湖盆三角洲骨架砂体的分析，对于三角洲砂体分布预测有重要意义。综合运用露头剖面以及粒度分析，对鄂尔多斯盆地东缘上三叠统延长组长7—长4+5三角洲沉积体系进行系统的研究, 探讨了沉积物粒度与河型之间的关系，识别出曲流型分流河道、辫状型分流河道沉积微相以及近缘水下分流河道、远缘水下分流河道沉积和席状化水下分流河道沉积，并且认识到长7—长4+5三角洲沉积体系内河道形态、砂体结构发生有规律的变化。研究表明，粒度因河型不同而迥异，偏度—峰态在不同河型中表现不同。

Characteristics of Grain Size of Delta Sandbody Framework in Yanchang Formation Upper Triassic, North Shaanxi

Delta sandbody is the most important large-scale continental-basin hydrocarbon reservoir in China,The a-nalysis of delta sandbody framework is very important to the prediction of delta sandbody. Based on the synthetical a-nalysis the outcrops profile and grain size analysis data, delta outcrops along the eastern margin of Ordos Basin. De-tailed study has been carried out on grain size and river Pattern at the Upper Triassic delta, the study demonstrate that the sandbody architecture and channel morphology should be happen to evolve regularly from the Chang 7 Member to Chang 4 + 5 Member in Yanchang Formation, and delta sand body framework is build including meandering distributa-ry channel, braided distributary channel, and submarginal subsurface distributary channel, distant subsurface distribu-tary channel and sheet-like subsurface distributary channel. The study suggests that lies different grain size parameter and Sk-Kg in different river Pattern.