THE CHARACTERS OF THE DEPOSITIONAL SYSTEMS AND SEQUENCE STRATIGRAPHY OF THE DEEP FAULTDOWN DEPRESSION IN THE LISHU DEPRESSION OF THE SONGLIAO BASIN

The Lishu Depression of the Songliao Basin can be divided into a faultdown depressionstructural sequence in the lower part and a depression structural sequence in the upperpart.The faultdown depression structural sequence could consist of four sub-sequences ofthe lower and middle parts of the Shahezi Formation,the Yingcheng Formation and theDeng louku Formation.In lower part of deep faultdown depression,the alluvial fan-fandelta system,delta system and lacustrine system are widespreaded,of which lacustrinesedimentary system takes a large proportion and could be considered as the main sourcerocks of hydrocarbons in the Lishu Depression,while the plaiting plains-type fan delta sandmassif and delta sand massif could be the main reservoirs in deep faultdown depression.This paper describes the stratigraphic sequence and petroliferous characters of deep fault-down depression based on the geological studies of the depositional systems and the forma-tion of sedimentary sequences.