Study On Sequence Stratigraphy And Sedimentary System Of The First And Second Member Of Shahejie Formation Of Paleogene In Qinan Area

TheQikou Depression is one of the largest hydrocarbon-rich sags in Bohai Bay Basin.Its source rocks have excellent conditions and abundant oil and g as supply capacity.Among them,the first and second members of PaleogeneSh ahejie Formation are one of the most important target strata in this area.The development degree of reservoirs directly affects the scale of hydrocarbon accu mulation.Strengthening the study of sequence stratigraphy and sedimentary syst em of target strata in the study area is an effective way to predict favorable r eservoirs.However,the study of sequence sediments in the first and second m ember of Shahejie Formation has not been thorough and controversial,and the influence of provenance on the supply range in different sedimentary periods i s not uniform at present.Therefore,further analysis of sequence stratigraphy an d development characteristics of sedimentary system in the 1st and 2nd membe rs of Shahejie Formation is of great significance to the exploration of hydrocar bon resources in Qinan area.Under the guidance of sequence stratigraphy,sedimentology,seismic stratig raphy and other theories,through the comprehensive analysis of 3D seismic dat a,core,outcrop,logging and other data,the first and second sections of Shahe jie Formation in Qikou Sag are detailed.Sequence sedimentation analysis and achieved the following main understanding.The combination of well and earthquake is divided into two third-order se quences,which correspond to the second section of Shahejie Formation and the second section of Shahejie Formation.Each sequence can be further divided i nto low water level,water inlet and high water level.The system domain,the sequence of the Sha-1 section corresponds roughly to the late Bohai Bay II.Through the comprehensive reflection of pre-earthquake reflection,stratum thickness,sand ratio and heavy minerals,it is indicated that there are two mai n source systems in the study area,namely Shaleitian bulge and Qizikou bulge,and Caofeidian 13-1 structural area.Low bulge only provides intermittent sour ce.Comprehensive 3D seismic facies identification,drilling core observation a nd single well logging phase characteristics analysis identified a variety of sedi mentary facies types such as fan delta,braided river delta,lake and lake botto m fan.Based on the comprehensive analysis of the joint well profile,plane sei smic facies,sand-ground ratio,stratigraphic thick map,sandstone and other thic k maps,the plane mapping and distribution characteristics of the sedimentary s ystem are analyzed: the sedimentary system of the Sha-1 section has obvious i nheritance.The developmental characteristics,in which the Shaleitian bulge is a steep slope zone,the developed fan delta-lake sedimentary system,the scorpio n sag is a gentle slope geomorphic background,and a typical braided river del ta-lake-lake bottom fan sedimentary system is developed.The fan delta front,t he braided river delta and the lake bottom fan can be used as important potent ial reservoirs in the first and second sections of the Shahejie Formation.