Structural Geometry And Kinematics Of Faults Of Paleogene In Dongying Depression

In recent years,with the exploration progress of Paleogene oil and gas resources in Dongying Depression,it is urgent to further study and re understand the structural framework,evolution and background of Paleogene in Dongying Depression.Based on the three-dimensional seismic data of Dongying depression,combined with drilling and logging data and core observation,this paper determines the structural deformation period,determines the fault development characteristics,carries out quantitative research on structural deformation,restores the structural evolution process on the basis of structural geometry and kinematics,and discusses the Paleogene dynamic background and structural genetic mechanism of the study area,The following achievements and understandings have been achieved:(1)By analyzing the unconformity,growth strata and contact relationship between faults and strata in the study area,there are four important tectonic stages in Dongying Depression since Paleogene: the transition stage from compression to extension during the Late Cretaceous and a short thermal subsidence phase during the early Paleogene epoch,the extensional rifting stage from the Paleogene epoch(2nd Mbr of the Kongdian Fm)to the early Eocene epoch(4th Mbr of Shahejie Fm),the strike-slip rifting stage from the late Eocene epoch(3rd Mbr of the Shahejie Fm)to the Oligocene epoch the(Dongying Fm)accompanied with the northward migration of depocenters,and the regional thermal subsidence and strike-slip stage during the Neogene epoch.(2)The main structural styles developed in the study area are determined,and the extensional structural styles are mainly developed in the early Paleogene Kongdian and 4th Mbr of Shahejie period;Strike slip structures were developed during the 3rd Mbr of the Shahejie and Dongying period,mainly in extensional and strike slip structural styles.The tectonic transition zone is generally developed in the area with low activity intensity of boundary faults,which is the result of unbalanced extension.(3)The activity characteristics of different parts of boundary faults in different periods are analyzed quantitatively.The activity intensity of the Paleogene boundary faults in the study area shows a trend of weak strong strong weak according to the structural stages.The activity intensity of the boundary faults in the west area(about 520 m/Ma)is larger than that in the east area(about350 m/Ma)in the first stage of Kongdian period;The eastern boundary fault activity continued to be intense(about 300 m/Ma)during 4th Mbr of Shahejie period,while the western boundary fault activity intensity of the study area decreased significantly.(4)According to the analysis of the structural evolution section,the eastern area of the study area(20.2%)is larger than the western area(11.4%)on the whole,the eastern area of the study area is more tensioned than the western area,and the tensile stress in EW direction(11.4%,20.2%)of the basin is also slightly greater than that in SN direction(7.8%,19.6%).(5)During the Paleogene,the study area experienced the structural transformation stage,inherited the Mesozoic basin prototype,deposited and filled,and the basin began to be rifted by extension;In the main extensional stage,the faults are less developed and the sedimentary thickness is large,and the boundary faults are the main active faults;At the same time,the NNE trending Tan Lu fault zone changed from left lateral strike slip to right lateral strike slip and developed strike slip structure;In the subsidence stage,the faults in the study area gradually die out and are in the whole depression and subsidence stage.Combined with previous studies,the subduction of the Pacific plate and the collision of the Indo European plate are the main driving forces for the formation of Paleogene structures.