Study On Paleogene Sedimentary System Of East China Sea Shelf Basin

The East China Sea Shelf Basin is one of the biggest Meso-Cenozoic basins in China offshore,and is rich in hydrocarbon resources.Therefore,petroleum exploration and development has crucial significance in the East China Sea,that it can alleviate the pressure of the shortage of petroleum resources in the China's southeast coast and upholding of state sovereignty.However,the complex geological features and low exploration degree of the basin resulting in the distribution of deposition system and petroleum both are unclear.There are two main problems existing in the exploration of the East China Sea Shelf Basin:first of all,the exploration degree in the basin is uneven,which mainly concentrated in the West Lake depression and Lishui-Jiaojiang depression,and lack of a unified sequence stratigraphic framework of the basin;secondly,there were not too much researches on the distribution and evolution of depositional systems,and the researches of the East China Sea Shelf Basin tectonic evolution and the influence of provenance to the depositional systems are still inadequate.In this thesis,on the foundation of earlier research results,under the guidance of the theory of Sequence Stratigraphy,Sedimentolody and Petroleum geology,on the base of well cores,well logging and seismic data,focusing on the Paleogene sedimentary evolution of East China Sea basin,following the research clue of point(single well)-line(profile)-map(plane)-tract(temporal evolution and spacial distribution),the stratigraphic framework of Paleogene succession has been built isochronously.Under this new isochronous stratigraphic framework,a new awareness of the type and distribution of the deposition systems has been received and its sedimentary evolution has been clarified.The main contents and conclusions of this thesis were listed as follows:?.In the tectonic evolution aspects:the East China Sea Shelf Basin is characterized by west-east differentiation and north-south dissimilitude in the tectonic pattern.Tectonic evolution experienced two main stages:rifting and depression and with distinctive vertical double-layer structure:the western area of the basin overlies half graben-shaped depression that faults on the east and overlaps on the west;the eastern part consists of double structure that early rifting and late depressing.Combing the characteristic of tectonic evolution with 15 seismic stratigraphic sections,the East China Sea shelf Basin is divided into 3 primary seismic sequences and 5 secondary seismic sequences.?.In the sedimentary facies aspects:fine interpretation of the multiple skeleton seismic lines has been done,and variety typical seismic facies in the study area are identified.With the application of seismic reflection features and identification marks of seismic facies to calibrate the profiles and recognize the sedimentary system in the study area initially on the base of seismic data.18 wells cores were observed and described,and sedimentary bar chart of the wells have been drew.What's more,a variety of depositional systems in existence are identified.III.In the aspects of depositional system and evolution:on influence of the tectonic evolution,it also presents the characteristic of "East-West zoning,North-South blocking".First of all,the western deposited earlier than the eastern,and in the terms of the type of depositional system,the western depression experienced continental,marine,marine-continental transitional enviroment and marine,and the eastern depression experienced continental,marine-continental transitional,marine enviroment,It has inherited some rules.In the eastern and western depression belt,the sedimentary environment both appeared marine in the southern and continental in the northern at different times.