Sedimentary Characteristics And Sandbodies Distribution Of The Third Member Of The Shahejie Formation In The Footwall Of The Shicun Fault In The Southern Slope Of The Dongying Sag

Taking the Third Member of the Shahejie Formation of Paleogene in the footwall of the Shicun Fault in the southern slope of the Dongying Sag as the researching area,making full use of drilling,well logging,seismic explanation,test analysis,and so on.The main types of sedimentary facies are identified,the sedimentary pattern and spatial-temporal evolution in the sand group level were summarized.The second sand groups of the Third Member of the Shahejie Formation of Paleogene in the footwall of the Shicun Fault in the southern slope of the Dongying Sag can be devided into 9 sub-layers accorading to the logging stratigraphy,sedimentary cycle,and so on.On the basis of 198 exploratory-well data,analysis for 343.5m cores,logging,seismic interpretation and grain size analysis,the sedimentary facies are identified,based on the research results above,the depositional pattern,spatial distribution pattern of sedimentary facies and distribution pattern of main sandbody are studied further.The sedimentary facies of the Shahejie Formation comprise delta,coastal shallow-lake facies,in addition,beach-bar is also in coastal shallow-lake.The delta developed in the southern part of study area,which include underwater distributary channel,underwater distributary interchannel,channel-mouth bar,frontal sheet sand and front sheet and the southeastern boundary developed delta plain subspecies flood plain.The coastal shallow-lake facies and beach developed the northern part of the study area,which is adjacent to the Shicun Fault;beach subfacies composed of sand and sand beach.The tectonic movement,paleoclimate and palaosource influence the sedimentary scope and evolution of the Third Member of the Shahejie Formation of Paleogene in the footwall of the Shicun Fault in the southern slope of the Dongying Sag.The Shicun Fault movement was active and migrating from the southeast to the west part of study area in the deposition period of the second sand group of the Third Member of the Shahejie Formation and the shape of sandbodies changed with it.Moreover,the paleoclimate was humid coupled with the palaosource supplying was enough,the delta developed in the study area.In the period of the first sand group of the Third Member of Shahejie Formation the climate was more dry and cool,the Shicun Fault activity weakened,the palaosource supplying weakened so the delta was retrogradation and the coastal shallow-lake facies and beach-bar was sporadically developed in the northern study area.