The Research Of The Basement Tectonic Characteristics Of Songliao Basin Based On Geophysical Methods

The formation and evolution of the basin is often concerned by people,and the nature and structural characteristics of the basin base are often neglected,but it is an important controlling factor for the formation and evolution of the basin.It is important to find out the structural characteristics of the basement of the basin and to explore the initial pattern of basin formation and the tectonic evolution in the later stage.Through the discussion of the mechanism of confirmation and evolution of the basement formation era and the distribution characteristics of the basement fault,we can understand the control effect of the basement on the internal tectonic evolution and formation deposition of the basin,and can better study the formation,migration and storage of oil and gas,and then guide the oil and gas exploration.Around the Songke ? Well Drilling Project,this paper collects recent research results on the basement of Songliao Basin,using geophysical methods such as gravity and magnetic exploration,electrical exploration and seismic exploration,making full use of the logging data of the Songke ?,gravity,electric and deep reflection seismic profiles and other geophysical data in the large area of Songliao basin.Absorbing the previous understanding of the area.Based on geophysical data,the interpretation of the deep reflection seismic profile of pine is completed,the gravity and electric data were comprehensively interpreted,and the drilling data in the study area were analyzed.The lithology,fracture properties and distribution laws of the basement and tectonic activities were taken as the main line to explore the structural characteristics of the basement.In this paper,the deep reflection seismic profile in the northern part of Songliao Basin is explained.The fine structure of lithosphere is described,and the basement formation of Songliao basin is discussed under the action of three continental shells of Siberian plate,North China Plate and Jiamusi block.And then under the action of three tectonic stresses in Paleo-Asian ocean closure,Mongolia-Okhotsk closure and the Paleo-Pacific subduction,the structural characteristics of the Songliao Basin basement were reconstructed.According to the characteristics of the reflection phase,the crust of Songliao basin is divided into three parts: the upper crust and the middle and lower crust have obvious reflection difference interface,the upper crustal is mainly inclined reflection in the East-west section,the bidirectional thrust nappe structure develops.In the lower part,it is a series of slip structures;the middle and lower crusts are alternately strong and weakly reflected,and there are many lenticular reflections in the upper and lower levels;and the Moho surface in this area shows the characteristics of flat and small fluctuation on the deep reflection seismic profile,butthere are many characteristics of the discontinuous,staggered and amplitude differences in the reflection seismic phase.According to the deep reflection seismic profile of Songshen?,? and ?,it is found that the Moho surface below Daqing appears obvious fault break,and the reflection of asymmetric ‘V' glyph appears on both sides,which is similar to the model of plate collage on the profile structure.The asymmetric ‘V' glyph reflection structure corresponds to the fracture position of the central fault Sunwu-Shuangliao in Songliao basin.On this basis,the hypothesis is put forward: This paper holds that the basement of Songliao Basin is combined along the Sunwu-Shuangliao fault under the action of tectonic stress in different directions provided by the three continental blocks.The basement of Songliao basin may be a splicing substrate,and on this basis,a rift basin has been formed and undergone a later transformation.In this paper,using the gravity and magnetic data to identify the fault system in the northern basement of the Songliao Basin by means of potential field separation and ILP(Improved Local Phase)boundary identification.Combined with the electrical structure of the Songliao Basin and the basic lithology data obtained through drilling,it is considered that this The deep fault zone of the area controls the distribution of the basement system.The tectonic properties of the central fault Sunwu-Shuangliao Fault in Songliao Basin are discussed.Through the great difference of geophysical response on both sides of the fault and the geological evidence on both sides of the fracture,combined with the regional dynamic action of this area,it is concluded that the Sunwu-Shuangliao fault is fractured by the splicing belt,and the plots on both sides of the fault are docked along The Sunwu-Shuangliao splicing belt constitutes a weak tectonic belt in this area,so the mantle uplift and lithosphere thinning in the mainland of Songliao Basin have great relationship with it.According to the paleogeographic and paleoenvironmental information on both sides of the fracture,it is speculated that the period of basal docking on the east and west sides of the basin may not be later than that of the early Permian.There has always been a great disagreement about the basement tectonic characteristics of Songliao basin.In this paper,after the fracture of Sunwu-Shuangliao fault is put forward,it is considered that the substrate of Songliao basin is a splicing substrate,and the plots on both sides of the splicing zone are ‘quasi-original'.Based on this foundation,a large amount of drilling data was collected.According to the analysis of the cores,some Precambrian metamorphic rocks(crystal basement)and Early Paleozoic-Middle Carboniferous shallow metamorphic rocks(including some Late Paleozoic Carboniferous Permian Sedimentation)existed in the basin basement.And multi-stage granites(Caledonian granite,Hercynian granite,Indosinian granite)controlled by the deep and large faults of the basement.