THE SEQUENCE STRATIGRAPHIC MODEL BASED ON THE VARIANCE OF RIVER LEVEL——TAKE THE GUDONG OILFIELD IN THE JIYANG DEPRESSION AS AN EXAMPLE

Taking the upper member of Guantao Formation of the Neogene in the Zhanhua Sag of the Ji-yang Depression,the Bohaiwan Basin as an example,a study of the high-resolution sequence stratigraphy has been carried out.Based on the study,the paper presents a new principle and method for identi-fying sequence.Using the data from the sedimentary structure character,lithology,color of rocks,the changing of clay types and geochemistry elements enrichment which reflect the change of river level,mark off the flooding system tract,high water level system tract and low water level system tract.The corresponding deposition processes of parasequence sets are flooding deposition,lateral accretion and slow deposition.Based on three system tracts,the facies model of four river types are established.