Basin Evolution Of Fangzheng Fault Depression And Its Control On Hydrocarbon Accumulation

Under the background of Tan Lu fault strike slip mechanism,fangzheng fault depression has experienced strike slip extension and strike slip compression multi-stage tectonic superposition.Seismic data have strong multi-resolution,the process of basin forming evolution is not clear,the prototype basin is difficult to identify,and the control of basin forming evolution on oil and gas accumulation is not clear This paper analyzes the strike slip basin forming mechanism of the Tan Lu fault zone,establishes the structural analytical model of Fangzheng fault depression,and defines the basin forming evolution stages and the control of basin forming evolution on oil and gas reservoirs.The quantitative research is shown in the analysis of the active rate of the main control faults,the identification of the active characteristics of the main control faults,the restoration of the prototype basin,the distribution and migration of sedimentary centers,and the determination of the strike slip uplift time,which provide a basis for the division of strike slip periods Therefore,this study has a certain guiding significance for the exploration of oil and gas reservoirs in Fangzheng fault depression,and has important theoretical significance for the study of the mechanism of strike slip basin formation.Based on the systematic analysis of the strike slip mechanism of the northern segment of the Tan Lu fault zone,it is considered that the basin forming mechanism has the characteristics of left lateral strike slip extension in the early stage and right lateral strike slip compression in the late stage.Due to the change of the strike slip direction,the transformation of the main fault controlling the strike slip and the strike of the main fault,the phenomenon of tension torsion compression torsion transformation occurred in Yitong Basin,fangzheng fault depression and Tangyuan fault depression Yitong Basin is controlled by western boundary fault.Based on the latest 2D and 3D seismic data interpretation of Fangzheng fault depression,three kinds of analytical models are established through stress model,theoretical model and grid model: extensional model,strike slip model and compressional thrust model.On the basis of the new analytical results,the structural pattern of Fangzheng fault depression is redefined.Different from previous studies,it is considered that the eastern boundary is developed with thrust nappe belt,which is similar to the eastern boundary The overthrust faults in the northwest margin of Yitong Basin have similar characteristics.Based on the analysis of the activity rate of the three major basin controlling faults,it is considered that the overall activity rate of the three major faults is weak in the Paleocene and Eocene(strike slip extension extension extension stage),and becomes stronger in the Oligocene(strike slip compression torsion transformation stage).The northwest margin fault moves northward,and the Yihantong fault and Southeast Margin Fault move southward,showing the characteristics of dextral strike slip.By using the fission track dating technique,the apatite fission track ages of the basement around Fangzheng fault depression are obviously located on several nodes.The first node is about 34 Ma,which corresponds to the beginning of Oligocene dextral strike slip in Fangzheng fault depression,the second node is about 23 Ma,which corresponds to the beginning of Neogene sinistral strike slip,and the third node is about 15-10 Ma,which is similar to this node It corresponds to the Miocene dextral strike slip and fault depression uplift.After 2.5 m A,it corresponds to the Quaternary dextral strike slip compression and fault depression rapid uplift.Based on this,the basin forming stage of Fangzheng fault depression can be divided into four stages: strike slip extension,strike slip tension torsion reversal,strike slip strong pull apart and strike slip compression torsion reversal.According to the restoration of prototype basin,the sedimentary center of Xin'ancun formation was located in Xingwang sub sag and dalinzi sub sag in the north,the sedimentary center of Dalianhe Formation moved southward in deshantun sub sag,the first member of Baotou migrated northward in deshantun sub sag,dalinzi sub sag and Xingwang sub sag,and the sedimentary center of Baoer member was located in deshantun sub sag and dalinzi sub sag on the southeast edge of fault In the early stage,it was controlled by the southeast margin fault,and in the late stage,it was controlled by the Yihantong fault.Based on the analysis of basin forming evolution,it is considered that the distribution of source rocks of Xin'ancun formation is controlled by strike slip extension period;the maturity of source rocks of Xin'ancun formation is promoted by strong strike slip extension period;a series of structural adjustment zones and thrust structural zones are formed in the eastern part of the fault depression during strike slip compression torsion reversal period.Combined with the analysis of oil and gas conditions,the reservoir forming model is established,and the near source,compressive and reverse faults are the main reservoir forming factors The newly interpreted Eastern thrust belt is located in the early sedimentary center,with developed reverse thrust faults and good trap effectiveness.It is considered that the eastern thrust belt is a favorable exploration area.