Sedimentary Characteristics and Petroleum Geological Significance of Ancient Shelf Sand Ridges:A Case Study of Lower Member of Silurian Kepingtage Formation in Tarim Basin
Yang Shuai
Liu Xiaofeng
Lu Yongchao
Yang Suju
Abstract：Ancient shelf sand ridge deposited in Lower member of Silurian Kepingtage Formation of Shuntuoguole uplift,Tarim basin,provides an ideal example to understand its sedimentary formation characteristics.By using well-logging and core data, shelf sand ridge is divided into 6 lithofacies:massive bedding medium-fine sandstone (FA1),hummocky cross bedding medi-um-fine sandstone (FA2),muddy conglomerate-bearing medium-fine sandstone (FA3),clay layer-bearing bimodal cross bed-ding fine sandstone (FA4),tidal bedding fine sandstone interbedded with mudstone (FA5),horizontal bedding shelf mudstone (FA6)according to the lithology and sedimentary structure of sediments.In terms of lithofacies association characteristics, shelf sand ridge whose deposits are affected by shelf tide and storm wave is classified into 4 sedimentary microfacies:sand ridge core microfacies (FA1-FA2-FA3),sand ridge inner margin microfacies (FA4),sand ridge external margin (FA5)and shelf mud microfacies (FA6).The plane distribution characteristics of shelf sand ridge along NE-SW and NW-SE are determined through detailed analysis of three-dimensional seismic slice attributes calibrated with well data.Ancient shelf sand ridge reser-voir has characteristics of extra low porosity and permeability,in which sand ridge core microfacies is better reservoir with av-erage porosity 6.96%,average permeability 0.34×10-3μm2 ,and is mainly industrial oil flow concentrated area.Syndeposition-al slightly anticline-lithologic traps are often formed since sandstones of shelf sand ridge present ridge or mound shape and draped by thick-layer shelf mudstone.
Keywords：ancient shelf sand ridgelithofaciesmicrofaciesKepingtage Formationpetroleum geologyTarim basin
Publication Date：2014-01-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：13( 858-870 )