Application of sequence stratigraphy to subtle reservoir exploration in Southern Songliao Basin

The distribution of subtle reservoir of Southern Songliao Basin is studied using the theories of sequence stratigraphy.Based on drilling,logging and seismic data,formation of depression period of Southern Songliao Basin be divided into nine third-order sequences,and third-order sequence is further divided into three systems tract or two systems tract.The paper discusses the sequence stratigraphy characteristic and the relationship of sequence stratigraphical units and oil and gas,reservoir combination of generation lower zones and preservation in upper zones is main in dichotomy sequence,reservoir combination of generation upper zones and preservation in lower zones is dominant in tripartition sequence.The results showed that the distribution of subtle reservoir is mainly controlled by surfaces of sequence,i.e.sequence boundary(SB),first flooding surface(FFS) and maximun flooding surfaces(MFS),the FFS is the important factor of controlling the formation of lithologic hydrocarbon reservoir in the lowstand system tract(LST),the SB and the FFS is the important factor of controlling the formation of stratigraphic hydrocarbon reservoir.