Sequence Stratigraphy And Depositional System In Steep Slope Zone Of Dongying Formation In The North Of The Liaodong Bay

In the study based on sequence stratigraphy,taking earthquake sedimentology,tectonic stratigraphic,basin analysis and geology of petroleum and natural gas as the guide,basied on the fine interpretation of logging and seismic profiles and,the sequence boundaries of Dongying Formation are identified;sequence division of Dongying Formation is carried on;and the sequence stratigraphic of the study region is estabilished.As a complete second-grade sequence,the internal of Dongying Formation can divided into three third-grade sequences(Sqdl,Sqd2 and Sqd3)according to the local epicontinental unconformity surfaces and its corresponding conformity surfaces.And then these third-grade sequences divided into fourth-grade sequences by using easier identified and traced regressive surfaces.Sqd2 sequence divided into d2x1 and d2x2.Sqd3 divided into d3-1,d3-2,and d3-3.In the study of logging facies,core facies and seismic facies analysis,six types of depositional systems are identified in Dongying Formation in the steep slope zone of the study area.They are fan delta,braided river delta,nearshore subaqueous fan,turbidite fan and deep-water argillaceous sedimentary system.And the composition of sedimentary facies in the main sequence and its distribution in the sequence stratigraphic framework are clarified.Through the analysis of controlling factor of depositional systems in the internal of sequence,we can find that tectonic activity,the lake level changes and source supply control the development of sequence and depositional systems in varying degrees.Tectonic movement is the most important impact controlling factor of sequence and deposition system.Lake level fluctuation change is the direct controlling factor of the formation of sequence boundaries.Source supply determine the main types of deposition in the lake basin.Depending on the diff erence of tectonic position,through the analysis of its oil and gas accumulation conditions,and combined with the distribution of depositional systems,two favorable areas are predicted,which are JX1 and JZ27 well area.