Characteristics And Formation Of Transfer Zone And Its Influence On Hydrocarbon Accumulation In Tiantai Slope,Xihu Sag

The geological structure and fault development characteristics of the Tiantai slope in Xihu Sag,East China Sea shelf basin are affected by the NW trending structural transformation zone,showing obvious zoning,and the structural transfer zone has an important impact on the trap,volcanic activity,sedimentary system,oil and gas migration and other reservoir forming factors in this area.Based on the analysis of the development characteristics of deep and shallow faults on the Tiantai slope,this paper defines the manifestations and structural attributes of the structural transfer zone,and analyzes the formation and evolution process and dynamic mechanism of the structural transfer zone in combination with the background of regional plate movement,The control of structural transfer zone on oil and gas accumulation is discussed.Many large NW trending detachment faults are developed in the deep Mesozoic of Tiantai slope,and the Mesozoic is characterized by a half graben structure with faults in the South and super faults in the north.Affected by the deep NW trending basement fault,the shallow Cenozoic mainly develops arc faults and reverse faults with small scale.Affected by the division and transformation of the structural transfer zone of the Tiantai slope,the South and north of the Tiantai slope have the structural characteristics of steep slope and gentle slope respectively,and the plane distribution of Cenozoic faults has obvious zoning.Under the influence of the Pacific plate movement,the structural transfer zone of Tiantai slope mainly experienced the formation and evolution process of gestation period,initial period,mature period and quiet period.It belongs to a discrete transformation fault zone formed by dextral strike slip activation in the later stage of NW trending basement fault.Different types of faults in Tiantai slope control the development of trap types such as fault nose,fault block and fault anticline,and the plane distribution of traps also shows a certain zoning.The segmented and combined growth characteristics of arc faults control the development process of traps.Magmatism mainly occurs along NW trending basement faults and affects the effectiveness of traps.The influence of the structural transfer zone on the sedimentary process is obvious in the sedimentary periods of the middle,upper and lower Pinghua members.The ancient fall of the arc fault changes obviously along the fault strike,and the fault segmentation points play an important role in controlling the transportation channel and enrichment position of the sand body.The oil and gas transportation system of Tiantai slope is mainly composed of fault sand body,which has the characteristics of "multi-storey building" as a whole.The study on the development characteristics of the structural transfer zone of Tiantai slope and its effect on oil and gas accumulation is conducive to an in-depth understanding of the law of oil and gas enrichment in this area,which has important scientific and practical guiding significance.