A Study On Tectonic Deformation Characteristics And Paleotectonic Environment Of The Yinggehai Basin During Depression

The Yinggehai Basin has a huge sedimentary thickness.Depression strata are the main target strata for oil and gas exploration.The development and distribution of source rocks,reservoirs and traps are closely related to the structural deformation in the basin Based on the actual seismic data and drilling data of the Yinggehai Basin and the regional tectonic background,this paper studies the Tectonic deformation characteristics of the Yinggehai Basin at different stages of depression.And based on the idea of tectonic controling of sedimentation and sedimentation reflecting of tectonic,this paper studies the stratigraphic sedimentary filling and structural development characteristics of the Yinggehai Basin at depression stage,deeply analyses the deformation and evolution Characteristics of the Yinggehai Basin at depression stage,including the detailed evolution history of the activity of the Honghe fault zone,the genetic mechanism and evolution history of the central diapir zone and the development characteristics of micro-faults.On this basis,through the compilation of the present seawater depth map and the stratum thickness map at depression stage of the Yinggehai basin,the Paleogeomorphological environment of the basin in Pliocene and Miocene was restored using to the method of "the present is the key to the past" and "proportional compensation" proposed in this paper,including the first restoration of the ancient seawater depth in the depression period of the Yinggehai Basin.In addition,the genetic mechanism of the waterway in the Ledong area,where a major breakthrough of natural gas exploration in the Yinggehai Basin is made recently,is deeply studied.And the physical simulation experiment of tectonic deformation in the Ledong area is carried out.The main achievements obtained in this paper are as follows:(1)being bounded by T30 seismic reflection interface,the depression stage of the Yinggehai Basin can be divided into two evolutionary stages depression stage and rapid subsidence,with different tectonic deformation characteristics.It’s defined that tectonic deformation,during one tectonic evolution stage,has a good inheritance.The diapirism in the basin,the development of continental shelf slope breaks and the paleotectonic geomorphologic environment are all controlled by tectonic deformation;(2)it is defined that the sinistral strike-slip activity of the Honghe fault zone terminated at 10.5 Ma(T40 seismic reflection interface)and the dextral strike-slip activity begins at 2.4 Ma(T27 seismic reflection interface)in the Yinggehai Basin;(3)the N-S trending "T" rupture caused by right-lateral strike-slip in the Honghe fault zone is the important factor for the formation of diapir,and the evolution of diapir is divided into four stages,pressurized stage,hyphosis stage,puncture stage,stabilization stage;(4)during the Miocene(T60-T30)of the Yinggehai Basin,the seawater paleo-depth was deep in the center and shallowed gradually towards the edge,forming a semi-enclosed bay sedimentary environment.It was predicted that good hydrocarbon source rocks were developed in the strata of Sanya Formation and Meishan Formation in the central deep depression belt of the Yinggehai Basin;(5)on the basis of Eocene tilted fault blocks,the waterway in the Ledong area of the Yinggehai Basin was formed because of the differential subsidence,caused by the drape anticline and the compound "Y" type collapse structure formed during the late oblique extension.Exploring the tectonic deformation characteristics of the Yinggehai Basin has guiding significance for the study on South China Sea and its adjacent basins and the further exploration and development of the Yinggehai Basin.