Stacking Patterns And Spatial-temporal Evolution Of Fluvial Sand Bodies In Typical Regions Of The Neogene,Shengli Shallow Sea Area

Based on the sedimentology theory and detailed description of key well cores,combined with the grain-size analysis and well logging,the paper analyzed sedimentary facies of the typical area,established the stacking patterns and spatial-temporal evolution of the Neogene fluvial sandstones in Shengli shallow sea area.Three types of rivers have been identified,including braided river,anabranched river and meandering river.The braided river deposits were mainly developed in the early stage of upper Guantao Formation of the block of Kendong12,the west of the Gudong 7th district,the block of Chengbei 22 and the late upper Guantao Formation of the block of Kendong 12.During the Ng5?Ng3,anabranched rivers prevailed in Kendong and Gudong area,while meandering river were developed in Chengbei area.Nine architecture elements,including mid-channel bar,channel bar,point bar,stagnant sediment,crevasse splay,abandoned channel,natural levee,overflow sand,floodplain,were identified.In addition to the floodplain mudstone constituting a four or five-level interface,the top or bottom interface of each architecture element is a four or five-level interface.Stacking patterns changed from cut-off and polygon type to isolated or independent type during Ng7?Ng3;accordingly,the spatial overlapping pattern of sand body is dominated from strip-shaped and sheet-like to lenticular shape.Stacking patterns changed from independent or isolated type to cut-off and polygon type during Ng3?Ng(1+2).Lateraly,from the block of Kedong 12 to the block of Chengbei 22,the development of the stacking gradually dismissed.The lateral stacking pattern changed from unilateral and polygonal to isolated,and the spatial stacking pattern of the sand body changed from strip and sheet to lenticular.