SEQUENCE STRATIGRAPHY CLASSIFICATION AND HYDROCARBON FEATURES IN THE SHALLOW LAYERS,NORTH SONGLIAO BASIN

Based on basin structural evolution characters,combining seismic and drilling data,sequence stratigraphy classification criterion of Sifangtai formation and Mingshui formation,upper Crataceous,north Songliao basin,is confirmed,also,the sequence configuration and inner sedimentary character of Sifangtai formation and Mingshui formation are analyzed.Songliao basin was in a press environment in Late Crataceous period,fluvial facies and flood plain facies are mainly developed,shallow lake and delta facies only occurred in local area.Sediments are mainly mahogany,green and off-white,which reflect oxidized and half-oxidized environment.On the other hand,the channel sand developed in Sifangtai formation can be favorable reservoir.In the same time,multiple phase fracture movement connects subjacent hydrocarbon,which provides rich oil sources for shallow layer oil accumulation.Argillite,widely developed in the late period of sequence Ⅰ,can effectively protect subjacent hydrocarbon.Complicated tectonic movement and effective accumulation-cap rock combination of shallow layer,north Songliao basin,make this layer possess potentiality of exploration activity.