The Characteristics And Extension Of Depositional System And Their Relationship With Hydrocarbon Distribution In Paleogene In North Margin Basins,South China Sea

As exploration development is continuously improved during the last thirty years,traditional research for single basin can not meet the current requirements of petroleum exploration and development in the marginal basins in northern South China Sea.Therefore,the study on correlation among marginal basins in north south china sea,and the relationship between depositional systems of different geological periods and hydrocarbon distribution,which are based on determination of the depositional systems,will show big practical significance for improving exploration.Terrestrial depositional system are the primary styps in Paleogene in north South China Sea.It is characterized by various of the marginal basins are characterized by multiple basin-type,complex basin structure,diversity of depositional system and sedimentary facies,multiple factors in controlling the petroleum reservoir.Therefore,the characteristics of evolution and distribution of depositional system have been researched in each basin,and the relationship between depositional system and petroleum distribution has been analyzed,based on the data of seismic and well logging,by establishing the stratigraphic framework of each basin and comparing the distributional diversity of depositional system in different series and subseries of Paleogene,And then the source-reservoir-caprock association has been discussed.The main achievement and innovation knowledge of the thesis are following:1.Each basin's Paleogene stratigraphic framework and internal structure have been built up.two-layered framework of stratigraphy-fault down and sub-basin up are developed in the margin basins of north South China Sea.Paleogene shows a tectonic framework of depression and uplift's alternating.Pearl River Mouth basin is rift basins,whose structure consists of half-gaben-gentle slope's faulted steps and gaben-asymmetric faulted steps.Qiongdongnan Basin is rift basins,whose depressions are of multiple structure and mainly of half-graben-gentle.Yinggehai basin is depression-type basin,and the mainly structures are symmetric.Beibu Gulf Basin is faulted basin,and the mainly are half-gaben-gentle.2.The direction of provenance of each basin was defined.Local provenance take the predominant place of Eocene in each basin,while in Lower Oligocene local provenance is subsidiary and the main provenance is uplifts around the basins.In Upper Oligocene the provenance is mainly provenance is uplifts around the basins and long distance rivers.Beibu-Gulf basin and Qiongdongnan basin haven not resource from river and the uplifts around are the predominant provenance.3.The types of depositional system and law of evolution have been defined in Paleogene.The main types of depositional system are lacustrine,alluvial plain,fan delta,delta and marine facies in Paleocene.The law of evolution totally shows early terrestrial facies and late marine facies,which reflects that depositional system has been controlled by structural evolution and fluctuation of sea-level.4.The relationship between depositional system and hydrocarbon distribution of each basin has been analyzed.Eocene of the marginal basin in North South China Sea generally developed fairly deep lake face and formed Wenchang and Liushagang Formation,which are two mainly oil source rock,in the Lower Oligocene have developed two mainly formation of the gas source rock,which are respectively Engping Formation of the alluvial swamp in the Pearl River Mouth Basin and the Yacheng Formation of the coastal swamp in the Qiongdongnan basin,and there are two favorable reserves distributed in the Upper Oligocene,sand rock of the shallow delta in the Zhuhai Formaiton of Pearl River Mouth Basin and fluvialite facies sand rock of the Weizhou Formation in the Beibu-Gulf basin,respectively,all of the above formed two favorable source-reservoir-caprock associations in the marginal basin,north South China Sea.