Numerical Simulation of Tidal Delta Sedimentation Based on Sedimentary Dynamics

Key words: 
• tidal delta /
• Sedimentary numerical simulation /
• evolutionary process

Abstract: Delta is not only an important part of sedimentology research, but also an important oil-gas enrichment layer in oil and gas exploration. The formation and development of deltas are completed by two or three sedimentary processes in rivers, tides and waves simultaneously. With the deepening of the research, the tide-controlled delta has gradually become the main target of oil and gas exploration and sedimentation research. However, due to the influence of hydrodynamic action, the sand body distribution law of the tide-controlled delta is unclear, the sedimentary facies combination is diverse, and the sedimentary system and characteristics are complex, which leads to great differences in the understanding of the sedimentary characteristics and sedimentary models of the tide-controlled delta. As for the basic research methods of tide-controlled delta, due to the lack of outcrop, the difficulty of sedimentary anatomy and the low resolution of logging interpretation data, there are some deviations in the research of tide-controlled delta. Based on the above problems, an idealized tide-controlled delta model was established by using the sedimentary numerical simulation method (Delft3D). By changing the conditions of river flow and tidal amplitude, the evolution law and main controlling factors of tide-controlled delta were explored. The results show that rivers and tides play different roles in the formation of tide-controlled deltas. Rivers transport sediments from the upper reaches, which accumulate in the estuary, and tides transport and deposit sediments from the upper reaches to the deep sea to form sand bars. With the increase of tidal amplitude, the dam body develops in a "flat" shape toward the sea. The shape of the dam body and the area of the delta are determined by the river flow and tidal amplitude. When the river flow and tidal amplitude increase, the sediment carrying capacity is enhanced, and the sediment can be deposited farther away from the estuary, and the area of the sand bar increases. At the same time, the erosion transformation of the original dam body is carried out, and the sand body is transported to the sea direction, and the average length of the dam body increases. The evolution of tide-controlled deltas can be divided into three periods: sediment accumulation in estuaries; The combination of river and tide transport sediment and form the dam body, and the delta develops rapidly. The delta area continues to grow, but the growth rate slows down.