Sedimentary Characteristics Of The Third Member Of Dongying Formation Of Paleogene In Dawangzhuang Area Of Raoyang Sag

The Dawangzhuang area is close to the Dawangzhuang structural belt and is located in the central-south area of the Raoyang Sag.The area has good oil-bearing properties in the third member of the Dongying Formation of Paleogene,which is a key area for oil and gas exploration and development.However,the structural environment in this area is complex and changeable,and is far away from the source area,which makes the sedimentary facies distribution complex,the reservoir types are diverse and the degree of heterogeneity is high.With the deepening of the exploitation degree,phenomena such as high water content and oil-water inversion have affected the way of oil and gas migration.Therefore,for the needs of reservoir prediction and further exploration and development,the study of the temporal and spatial distribution of sand bodies and sedimentary facies has become the key to the next exploration work in this area.Based on the previous analysis of the structural background of the Raoyang Sag,the thesis used the principles of sedimentology to make full use of drilling data,sedimentary structural signs,logging data,paleontology and other geological data.This time combined with seismic interpretation,the maximum entropy spectrum analysis technique is used to divide the stratigraphic sequence.The thesis analyzes the influence of buried hill belts,depressions and slopes in the central Raoyang Sag during the deposition period of the third member of the Dongying Formation on the provenance direction,rock composition and sedimentary facies type of the study area.In this study,the sedimentary environment,the characteristics of the spatiotemporal distribution of sand bodies and the law of sedimentary evolution in the Dawangzhuang area were studied.This time,the provenance direction and the type of sedimentary microfacies in this area were determined,and the depositional model of the third member of the Dongying Formation was established.This study shows that during the deposition period of the third member of the Dongying Formation,the climate in Dawangzhuang area was relatively warm and humid,under strong hydrodynamic conditions of strong oxidation-weak oxidation.The provenance comes from the Shenze low uplift in the southwest of the study area,and the deposition center is located in the northeast of the study area.The Dawangzhuang area has a finer grain size,mainly light gray fine sandstone and fuchsia mudstone,and the sandstone structure has a high degree of maturity,indicating that the area is far away from the source,located in the downstream of the river and the terrain is relatively flat.The study area developed meandering river facies,and subdivided five types of microfacies,such as channel filling deposit,point bars,crevasse-splay deposit,natural levee,and floodplains.The III and V oil groups of the third member of the Dongying Formation in the area are the main oil-bearing parts.The point sand bar sand body is well developed and is a high-quality reservoir facies.The meticulous research on the type of sedimentary facies provides support for the development strategy of Dawangzhuang Oilfield and provides a geological basis for reservoir prediction.