Subtle lithologic reservoirs with shallow burial depth in the Ⅱ-Ⅰ Fms of Fuyu oil layers (FⅡ-FⅠ) are widely distributed in Sanzhao Depression

Songliao Basin

and are the major targets of tight oil exploration for reserve growth.The FⅡ-FⅠ in Sanzhao Depression are dominated by shallow water delta depositional systems featuring in complex change of sedimentary facies belt

and their main reservoir frameworks consist of distributary channel sandbodies.Based on detailed core observation of 53 wells and combining with logging data of more than 1 000 wells

11 types of lithofacies were recognized in the distributary channel sandbodies of FⅡ-FⅠ in study area

and they were grouped into 3 lithofacies associations according to different datum level cycles.There are three types of interlayers in single distributary channel

including muddy interlayer

calcareous interlayer and conglomeratic siltstone

by which the internal architecture configuration of single distributary channel sand body was further analyzed.Comparison models for cotemporaneous channel sandbodies and interlayers were built through flattening of the tops of distributary channel sandbodies and were used to compare the sandbodies in respects of lithology

types of interlayer and shapes of logging curve.Methods were proposed for identifying the interwell cotemporaneous channel sandbodies between wells with small spacing within the sequence stratigraphic framework and the distribution of sandbodies was also discussed.Based on the comparative method above

combining with comparison of sandbodies by fence diagram and seismic attribute analysis

the distribution characteristics of single distributary channel sandbody were described

providing a geologic foundation for tight oil exploration and development.