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

Key words: 
• grain size analysis

Abstract: Delta sandbody is the most important largescale continentalbasin hydrocarbon reservoir in China,The analysis of delta sandbody framework is very important to the prediction of delta sandbody. Based on the synthetical analysis the outcrops profile and grain size analysis data, delta outcrops along the eastern margin of Ordos Basin. Detailed 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 distributary channel, braided distributary channel, and submarginal subsurface distributary channel,distant subsurface distributary channel and sheetlike subsurface distributary channel.The study suggests that lies different grain size parameter and SkKg in different river Pattern.