The Study Of Sequence Stratigraphy And Depositional Facies Of Huagang Formationin Of Xihu Depression East China Sea

The study area in this paper is Xihu depression in East China Sea,and the target layer is Huagang formation of Paleogene.Based on the study of the biostratum,sequence stratigraphy,sedimentaty facies and reservoir at home and abroad,directes by the theory of sequence stratigraphy,which combines well drilling,well logging and the analysis of seismic,divides the sequence and tract of the single well,and the compares the profile.After that,the framework of the sequence stratigraphy is built up and the paper detailed analyzed the combination of the sedimentary facies and the system tract.The paper researches the plane distributes of the sedimentary facies with the system tract as the equitime unit and confirms the major control factor and theevolution of the sequcenc.On the top of that,directed by the theory of the sedimentation and reservoir geology,the author overall utilizes the core and the thin section.On the base of the researches the relationships between sequence and the combination of reservoir.Get the distribution of reservoir sand.Further study the relationship of sequence stratigraphy and sedimentary facies of reservoirThe Jilong movement,Yandang movement,Oujiang movement,Yuquan movement and Huagang movement has significant influence for Xihu depression.Huagang movement in late Oligocene-early Miocene has made regional angular unconformities in the basin and lead to stratigraphic gap.Huagang movement correspond to the cooling event of Paleogene / Neogene global change of Mi-1(First Miocene Glacial).Due to the incident,the Antarctic ice sheet expanded to the current 1.2 times the mass of ice sheets,and accompanied by about 50 m sea level decline and a series of influence.Based on the former study of sedimentary facies in this area,utilize the core,thin section andpaleontology,combined the petrological characteristics,sedimentary structure,well logging and analysis of seismic data,achieve that it is mainly developed wetland fan delta,in part area developed shallow lake environment,the nearshore subaqueous fan was developed in folded region near Diaoyu Islands.Take Vail's sequence stratigraphy as a theoretical foundation,the rock strata,biostratigraphy,chronostratigraphy,comprehensive study of seismic stratigraphy,depositional systems and structural geology with the background analysis,there can be identified 4 sequence boundaries(SSB4(SB4)/SB5/SB6/SSB5)and 3inside boundaries(mfs4/mfs5/mfs6),include uplift angle unconformity and erosional unconformity and thus divide 1 second sequence(SSQ4)and 3 third-order sequence(SQ4/AQ5/SQ6).And there were only transgressive systems tract and high-stand systems tract developed.According to the analysis of 12 mainly section and dozens ofassistant section,build up the sequence stratigraphic framework of Huagang formation,analyse the controlling factor of the third-order sequence and setup the sedimentary model in study area.Finally,combinating sedimentary,sequence stratigraphy,reservoir characteristics and hydrocarbon results of the study area.Analysising of the sedimentary sequence and the relationship between the reservoir,consider that good condition reservoir located in the delta plain distributary channel sand body and delta front mouth bar sand body and underwater distributary channel sand body;Near stratigraphic sequence interface exposed to denudation for atmospheric fresh water dissolution...