Deformation And Evolution Characteristics Of Pre-Paleogene Faults In The Southern Part Of Liaoxi Uplift

The southern part of Liaoxi uplift is located at the intersection of Liaodong Bay depression and Bozhong depression in Bohai Sea.The east and west sides are respectively surrounded by Qinnan sag and Bozhong sag.The petroleum geological conditions are superior.In recent years,many oil and gas reservoirs have been found in the pre-Paleogene.However,the study on the development characteristics and evolution characteristics of pre-Paleogene faults in this area is weak.In this paper,the latest three-dimensional seismic data and drilling data are used to systematically study the development characteristics of the pre-Paleogene,the deformation and evolution characteristics of faults and the influence range of fault damage zones in the southern part of the Liaoxi uplift and its adjacent areas by means of seismic fine interpretation,the analysis of unconformity characteristics,the balanced evolution profile technology and the seismic variance attribute value.The results show that the Archaeozoic,Paleozoic and Mesozoic developed in the pre-Palaeogene of the southern part of the western Liaoning uplift.The Paleozoic loses in the tipping end of the southern section of Liaoxi uplift and the northern part of the Shijiutuo uplift,and the Mesozoic loses in the eastern tipping end of the Shijiutuo uplift and the southern part of Liaoxi uplift.The fault properties are mainly negative inversion fault,extensional strike-slip composite fault and extensional fault.Negative inversion faults control Paleozoic distribution,and extensional strike-slip composite faults control Mesozoic distribution.On the profile,the pre-Palaeogene faults are mostly shovel-type and plate-type,and they are combined to form a variety of styles,such as thin-based –bald-based,flower-like,’X’-type,’y’-type,domino,and graben-and-horst.In the plane,the faults are mainly composed of parallel type,oblique type,echelon type and horsetail type.At the same time,with the change of regional stress field since Mesozoic,the number and dominant trend of different interface faults are different.From the deep NW-trending and nearly EW-trending faults,the shallow layer mainly develops NE-trending faults.According to the regional evolution background and stratigraphic development characteristics,the faults are divided into 6 active periods of early-late of Indosinian periods,early-middle-late of Yanshanian periods and Himalayan periods.According to the structural-genetic classification,the pre-Paleogene buried hills are divided into 9 models and 26 types.In addition,combined with the development characteristics of pre-Palaeogene strata and the development stages of faults,the evolution process of buried hill in the southern part of Liaoxi uplift and its adjacent areas is divided into the embryonic stage,the finalization stage,the transformation stage and the deep burial stage of buried hill by compiling the tectonic evolution profile.The width of fault damage zones on the top surface of buried hill are between several hundred meters and several kilometers,and the influence of fault damage zones on buried hill igneous rock are stronger than that of clastic rock.