Simulation Experiment of Shallow Meandering River Delta Sedimentation in the 2nd Member of the Shanxi Formation in Yan'an,Ordos Basin
[Objective]Exploration has shown that the sand body of the Shanxi Formation,the main gas producing layer in the Yan 'an gas field in the southeastern Ordos Basin,is distributed in a long and narrow strip,which is significantly different from its distribution in the north. It is of great significance to clarify the genesis mechanism of the sand body in the 2nd member of Shanxi Formation for understanding the distribution pattern of sand bodies in the area.[Methods]Taking the 2nd member of the Shanxi Formation in the southeastern basin as the geological proto-type,a flume sedimentation simulation experiment was used to investigate the sand formation,evolution process,and control factors.[Results and Conclusions]The gentle slope and low flow intensity of the 2nd member of the Shanxi Formation distributary channel is an important factor in the low sinuosity of the meandering flow state,and the horizontal amplitude rate is a key feature in the longitudinal extension of the sand body,sand size,aspect ratio of the coast,and change of flow control. The extension of the entire distance and length-width ratio of the sand were propor-tional to the scale and rate of water withdrawal. During the sedimentary period of the Shanxi Formation,the water level dropped significantly,and the shoreline migrated a long distance to the lake area. The water inlet retreated frequently,and the sand in the front of the meandering river delta extended a long distance. The sand superposition style has the characteristics of "vertical superposition","vertical cutting",and "lateral migration". The results are of great significance to the prediction of sand bodies in the Shanxi Formation and the search for high-quality reservoirs.
flume simulation experimentshallow meander river deltasand control mechanism2nd member of the Shanxi FormationOrdos Basin
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