Study on the Sedimentary Characteristics and Evolution laws of Sandy Braided River Delta Based on Sediment Numerical Simulation

Key words: 
• sandy braided river delta /
• sedimentary numerical simulation /
• distributary sand bar /
• sedimentary model /
• evolution

Abstract: [Objective]The research on sandy braided river delta has lots of achievements, but the sedimentary characteristics and evolution laws of sandy braided river delta keep different views, especially the understanding of mouth bars and distributary sand bars needs to be further study.[Methods]Based on the underground reservoir data, the paper uses the Delft3D software to show the growth and evolution process of the sandy braided river delta into the lake, summarizing it’ s sedimentary characteristics and evolution laws.[Results]The evolution of sandy braided river delta has three stages.In the early stage,the delta grows fastest, and the average diameter growth rate was greater than 6m/step. Sediments are carried into the lake and quickly unloaded, forming a large flower-shaped mouth bar under the water. In the middle stage, the delta plain keeps growing, the delta front keeps large,accounting for more than 50% of the delta. Contiguous sand bodies are built. In the late stage, the delta grows slowly, the average diameter growth rate is maintained at 1m/step.The front area is small, less than 20 % of the overall area.The delta plain has many distributary channels and ditches.There are many ways to transform the distributary sand bars.The delta front sand bars have different degrees of superposition relationship and rhythm combination characteristics, and the distributary sand bars are built on the residual mouth bar.[Conclusions]The sedimentary model of sandy braided river delta was established, which can provides reference for the genetic identification of distributary sand bars and mouth bars for the better study of underground reservoir architecture.