An Analysis On Sedimentary System In Shahejie Formation At The Gentle Slope Of Huanghua Depression

Huanghua Depression is located in the Bohai Bay Basin,Chengbei Zone islocated in the southeast of Huanghua Depression,in the neighborhood of ChengningUplift.It is a special gentle slope caused by the fault.The research on thecharacteristics of sedimentary in gentle slope is rare. There are four extensionalnormal faults with the NNW dip shift,named the South of Yang Er Zhuang Fault,ZhaoBei-Yang Er Zhuang Fault,Zhang Dong-Hai4Fault and Qi Qong Fault,whichconstitute the Chengbei fault-step belt framework falling downwards step by step.Asdemonstrated by many years’ petroleum exploration,there has abundant of petroleumresources in Shahejie Formation of Paleogene.However,the degree of exploration isrelative lower.It is not adequately realized the particularity and controlling-factorscaused by the sequences and depositional systems of the gentle slope belt,from theearlier researches and works.Through the analyses of drilling core face,well log face and seismic face,thepaper identifies3types of sedimentary system,namely delta,lake and gravity currentsedimentary system.Based on the datas of drilling core,abundant3-D seismic data,core data andlogging data,utilizating the method of continental sequence stratigraphy,according tothe characteristics of different levels of sequence boundaries,the paper dividesPaleogene into two second-order sequence,and divides Shahejie Formation into sixthird-order sequence.It uses third-order sequence as cell to constitute the regionsequence stratigraphic framework.On the basis of constitution of region sequence stratigraphic framework,referringto the analysis of Paleo-provenances,the percent of sandstone,seismic face andseismic information,the paper analyses the distribution and evolution of sedimentary system of each sequence.On basis of the above research,it analyses the distributions on space andevolution rules on time of the depositional systems.On space,from southernChengning Uplift to northern Qikou Depression,the depositional systems were erasedin the slope zone,developed braid river delta plain in outer zone,braid river delta frontand sand-bar in middle zone,and braid river delta front and turbidite fan in inner zone.It constitutes the gentle slope depositional system pattern of Shahejie Formation inChengbei fault-step belt in the Huanghua Depression,which is built up by delta,lakeand gravity current.