Study On Sedimentary Facies Of Dongying Formation In North Slope Of Chengdong

The research area is located in the northern slope of Chengdong uplift in Jiyang depression.Since 80s,a lot of exploration work has been carried out for the northeast slope of Chengdong.In Dongying block C112-1,the area of oil exploration is 1.1km2,and the petroleum geological reserve is 68*10~4t.In order to clarify the exploration potential of Dongying formation in Chengbei slope,sedimentary facies study and favorable facies belt prediction are carried out.Based on the existing core,lithology,logging and seismic data,the Dongying formation is divided into 3 sections and 5 sand formations by using the stratigraphic division method to identify the division signs.The formation of the Dongying formation in the western part of the northeast slope is incomplete,lacking the upper sand group and the fourth and fifth sand beds.Identify lithologic marks,logging facies marks and seismic facies marks,and identify the 5 facies types of Braided River Delta,nearshore subaqueous fan,lacustrine facies,beach bar and turbidite fan in Dongying formation.The distribution characteristics of the sedimentary facies are studied in 3 aspects:the source area analysis and the vertical,section and plane aspects.On this basis,combined with the Dongying formation depositional evolution,sedimentary facies control factors identified are:change and lake level fluctuation of tectonic movement,climate change,the eventual establishment of Dongying group in early and mid lake facies,sedimentary facies model advanced braided river delta facies,nearshore subaqueous fan.The sand bodies in the study area are mainly developed in the eastern part of the braided river delta front subaqueous distributary channel sand bodies.The sand bodies are abundant in number,large in thickness and large in scope,but the sand layer is too thick,which also increases the difficulty of sealing.The nearshore subaqueous fan,beach bar and turbidite also develop favorable sand bodies.The sedimentary layer of the deep lake mudstone in the east two and the East three segments is rich in organic matter and is a favorable reservoir.The mudstone layer of the top unconformity and the east two section of the Dongying formation can be used as a cover.2 favorable targets are predicted by combining the development of sand body in the study area and the configuration conditions of the reservoir,reservoir and cover.