Analysis Of Sequence Stratigraphic Characteristics And Controlling Factors Of Shahejie Formation In Cangdong Sag

This study is based on the "comprehensive geological study of Shahejie formation in Cangdong sag" project of CNPC Dagang oilfield company.Due to the divergence of sequence division and fine contrast of Shahejie formation in Cangdong sag,the regional characteristics of sandbody distribution are uncertain,which is not conducive to the delineation of favorable zones.Based on the theories of seismic stratigraphy,sequence stratigraphy,terrestrial sequence stratigraphy and high-resolution sequence stratigraphy,this study conducts sequence stratigraphy division and correlation by collecting,interpreting and analyzing seismic,drilling,logging and core data.Six three-level sequence interfaces are identified,and the Shahejie formation in cangdong depression is divided into five three-level sequences,which correspond to the lower 3rd Member of Shahejie Formation,the middle 3rd Member of Shahejie Formation,the upper 3rd Member of Shahejie Formation,the 2nd Mmember of Shahejie Formation and the 1st Member of Shahejie Formation.Based on the understanding of the fourth-order sequence,it is further divided into 13 four-level sequences and discussed in detail the internal structure of the sequence and the superposition style of the quasi-sequence.The isochronal sequence stratigraphic framework of Cangdong depression is established.The overall stratum thickness is thick in the northwest and thin in the southeast.The characteristics of stratigraphic sedimentary development in each sequence period are different.Guided by the analysis of the main controlling factors of sequence strata of Shahejie Formation in Cangdong sag,it is concluded that tectonic movement and paleoclimatic conditions have the greatest influence on the development of sequence strata in the study area.There are differences in stratigraphic distribution,sequence stratigraphic framework and sand body distribution in each sequence period,indicating that tectonic movement and paleoclimatic conditions are different in the five periods.Sequence?-?period mainly for stretch-strike-slip movement structure and continue to strengthen,the climate is warm and humid subtropical climate;Sequence for ?strike-slip tectonic movement,paleoclimate condition for warm semiarid subtropical climate;Sequence ? for stretch-strike-slip movement during the period of construction,the climate is warm subtropical climate.By analyzing the paleo-drop of boundary faults in cangdong and xuxi,the response relationship between structure and sedimentation is further verified.In sequence stratigraphic framework was established,the response of the relationship between structure and sedimentary building of Cangdong sag of Shahejie Formation sequence stratigraphy development mode and filling evolution rule,and then analysis the control factors of sequence stratigraphy in the study area is the tectonic movement and ancient climate change,which has guiding significance for oil and gas exploration in the Shahejie period of the Formation of Cangdong sag.