Study On The Sedimentary System Of The Middle Shahejie Formation In Dongpu Depression

Dongpu depression,a typical petroliferous Cenozoic basin,is located at the southwest of the Bohai Bay rift basin.Changyuan,Lankao,Dongming,Puyang and some other regions are the main oil producing areas.At present,the distribution rules and main controlling factors of provenance and depositional system of Sha-2 and Sha-3formations in the area are not clear,which seriously restricts the next step of oil and gas exploration and development.Based on the theory of sequence stratigraphy and sedimentology,this paper mainly uses core,logging and seismic data to carry out a comprehensive study of sequence stratigraphy and sedimentary system in the south-southwest depression of the Dongpu depression,and the target strata are the upper of the Paleogene Sha-2 and Sha-3 formations.Based on the data of core and logging,multi well cycle comparison is carried out according to the base level cycle comparison theory.The subsection of the Shahe Street Group in the south of the Dongpu depression,the upper subsection of the Sha-3 formation and the lower two subsections of the sand are divided into 3 long-term cycles(Es~3,Es~3,Es~2),and 9 mid-term cycles.The comprehensive analysis of the composition maturity and paleogeomorphology of heavy minerals and debris suggests that the source of the south of Dongpu depression mainly comes from three directions:southwestward,West and East,and four source sink areas,two sources and sinks in the southwest,a source and remittance area in the East and a source and sink area in the west,and the core and log facies analysis think Dongpu depression is considered.A large meandering river delta shallow lake depositional system is mainly developed in the Sha-3 formation of Southwest China.The delta is characterized by"small plain and large front",mainly developing the subaqueous distributary channel of the delta front,and the lithology is thick and thin sandstone with thin and purple red mudstone,and the wedge-shaped and trough like interlaced bedding and climbing ripple bedding are widely developed.In addition,due to the influence of the the Yellow River fault,the meandering river delta has been advancing to the central of the lake basin from the south-west direction of the study area to the northeast of the study area,and the West and eastern part of the ascending plate are supplied by the ancient gully Valley to the central of the lake basin.The whole is the source of the source of"long axis sand transport,short shaft recharge",and the two sections of sand.The water is shallow,and the subsection of the Sha-2 formation is characterized by shallow water delta deposits,showing the characteristics of"large plain,small front edge",and the former delta developed turbidite deposit due to the influence of fracture fracture zone.In this study,the upper subsection of the Shahejie group Sha-3 Formation is controlled under the control of the uneven settlement of the fault in the Changyuan fault.The formation of the Oolitic Limestone beach dam is an important exploration target for the future remaining oil.