Reservoir-seal associations in the shallow sequence stratigraphic framework in northern Songliao Basin

In the light of seismic data and well logs,the present paper deals with the construction of the sequence stratigraphic framework in the shallow strata,analysis of the sedimentary facies in individual systems tracts,and development of the reservoir rocks and seal rocks and their disposition in northern Songliao Basin.The reservoir rocks consist of fluvial sandstones in the transgressive systems tract,and deltaic sandstones and littoral and shallow lake beach-bar sandstones in the regressive systems tract in the Sifangtai Formation in the Qijia-Gulong depression,Longhu-Da’an terraces,southern Changyuan and Sanzhao depression.The seal rocks are composed of mudstones above or below the maximum flooding surface in individual sequences.The mudstones in the lower sequences of the Sifangtai Formation are only regional seal rocks,while those in the middle and upper parts of it and those in the sequences of the first member of the Mingshui Formation are considered as relatively favourable seal rocks.