Research On Sequence Stratigraphy And Sedimentary Facies Of Palaeogene Of Member 3 And 4 Of Shahejie Formation In Langgu Depression

The paper is based on the latest regional high resolution 3D seismic data,according to the theory of sequence stratigraphy,combining with the comprehensive utilization of dr illing,well logging,lithology and other geological data to conduct the research of sequenc e and sedimentary system in Paleogene in Member 3 and 4 of Shahejie Formation in L anggu Depression.Through the combination of well-seismic,a particular sequence stratigraphic study is carried out for the Paleogene,the 4 types of key sequence boundaries to control 2nd and 3^rd order sequence are identified,which are regional unconformity,uplift unconformity,parall el unconformity and partial unconformity.The object layers are divided into two 2nd order sequence,eight 3^rd order sequence,the recognition features of 3^rd order sequence and inte rnal system tracts are also be discussed.The type,development characteristics and scale is controlled by provenance,lake level fluctuation,palaeogeomorphology and other factors.There are two major provenance regio ns in Member 3 and 4 of Shahejie Formation in Langgu Depression.One is the braided fan,sublacustrine fan and semi-lake sedimentary facies sequence formed from east to wes t,which is developed in the 4^th Member of Shahejie Formation from the SE in the Cang xian uplift provenance system.Another is the nearshroe subaqueous fan fan delta sublacus trine fan semilake sedimentary facies sequence formed west to east,which is developed i n the 3^rd Member of Shahejie Formation from the west in Daxing uplift provenance syst em.Braided delta and sublacustrine fan are developed in the provenance from the Cang xian uplift in SE.Nearshore subaqueous fan,fan delta and sublacustrine fan are developed in the provenance from Daxing uplift. Nearshore subaqueous fan,sublacustrine fan and s emi-lake facies are mainly developed in the lower segment of Shahejie 3^rd Member.In th e middle segment of 3^rd Member of Shahejie Formation developed nearshore subaqueou s fan,fan delta and sublacustrine fan.In the upper segment of 3^rd Member of Shahejie F ormation developed fan delta and braided fan sedimentary system.Favorable reservoir facies belts for formation of lithologic stratigraphic reservoirs are predicted in three areas,which are the northwest wing of Daliuquan nose structure zone,central depression area and western zone of Hexiwu tectonic zone.