Sedimentary System And Depositional Evolution Of Es₄ In Shengtuo Area Of Dongying Depression

The lateral and vertical distribution of deep glutenite is now the difficult and crucial part of Shengtuo area.This study will start with the sedimentary characteristic of deep glutenite and use Es4 member as the interest interval,comprehensively using geology,seismology,well logging,analysis and assay data to develop the research.The main research contents include: sequence stratigraphic division,rock facies analysis,geophysical facies analysis,sedimentary facies distribution analysis,sedimentary evolution and sedimentary model analysis,etc.The main results achieved are the following 4 aspects:(1)Identify the stratigraphic development and tectonic characteristics of Es4 member in Shengtuo area,using the way in which combining the well logging and seismology to divide the Es4 member into six fourth-order sequences(SQ1?SQ2?SQ3?SQ4?SQ5?SQ6).The high frequency of tectonic activity of chennan fault control the formation structure of Shengtuo area of Es4 section.Each sequence has the overlapping phenomenon and rising half cycle as the main characteristics.Internal sequence interface is a high frequency tectonic cycle interface.(2)Summarize the type of depositional facies in the study area including nearshore subaqueous fan facies,fan-shaped delta facies,alluvial fan facies,deep water turbidite fan facies,shallow-deep lake facies.The alluvial fan facies and nearshore subaqueous fan locate in the northern edge of the sag with large scale.Turbidity fan is not large,and is distributed in the deep lake at the front of the underwater fan.The direction of the sedimentary source of the study area is both from the northeast to the southwest and from northwest to the southeast.Chenjiazhuang is the main sedimentary source of the study area.By SQ1 to SQ6 deposition fan body formed obvious retrogradation sedimentary evolution characteristics,the sequence also has retrogradation sedimentary characteristics,reflect the intermittent expansion of lake basin sedimentary evolution process.(3)Vertically,the fan facies presents many times of the stack overlap characteristics,channel and inter-channel present many times in each sequence.On the plane,the seismic facies analysis based on RMS attribute can accurately divided subfacies,determine the facies boundary.(4)Summarize the evolutionary discipline of the study area,regarding Es4 member of the Shengtuo ancient gully as multiple source overlying filling pattern,thinking of ancient gully as the passage through which terrigenous clastic rock get into the lake basin.The multiphase tectonic activity lead to a series nearshore subaqueous fan-lake systems combined on the plane and retrogradely superimposed in the vertical.The evolution of the whole depositional period is from the lower segment of Es4 member to the upper sub-segment of Es4 member,which underwent the alluvial fan-nearshore subaqueous fan-fan delta depositional filling process.