The Function Of Fault Superposition In No.2 Structure And No.3 Structure Of Nanpu Sag

Nanpu Sag is a secondary hydrocarbon-rich sag in Huanghua Depression,Bohai Bay Basin.Its structural belts 2 and 3 are favorable areas for oil and gas exploration and development.Complex fault systems are developed,which control the sedimentary filling,hydrocarbon migration and trap formation of the basin.With the further exploration and development of structural belts 2 and 3 in Nanpu Depression,it is necessary to clarify the stages and processes of the vertical development and evolution of faults,study the characteristics and laws of fault superimposition in different periods,summarize the typical manifestations of fault superimposition in this area,and systematically analyze the control of fault superimposition on hydrocarbon migration,accumulation and distribution.? Based on the high-definition three-dimensional seismic data of Nanpu Depression,this paper analyses the active period,morphological characteristics,fault strike,fault activity and fault evolution history of the faults in the study area,summarizes the specific manifestations of superimposed fault action in the study area and summarizes its typical patterns.On the basis of this theory,this study also designed a series of physical simulation experiments of plane and section sandbox to verify the control of faults on the development of late faults and the influence on the formation of structural combination patterns,and the relationship between late fault activity and early fault strike.The following conclusions have been obtained in this paper:(1)The strike of the early fault is perpendicular to the extension direction of the late tectonic movement,and a nearly parallel late fault is formed in the late tectonic activity.Under the same other circumstances,the fault activity near the direction of the tectonic extension is greater;and(2)the strike of the early fault is obliquely intersected with the extension direction of the late tectonic movement,in which case,the late fault is formed.The initial strike of the stratum should be nearly parallel to the early fault,and deflect from bottom to top perpendicular to the extensional direction.At the same time,the strike and activity intensity of the stratum in different sedimentary horizons change.3.The strike of the early fault is nearly parallel to the extension direction of the late tectonic movement.Under this condition,the fault in the study area no longer occurs and has no influence on the development of the late fault.If the basement pre-existing faults remain active after the first member of the Shahejie Formation is deposited in the later stage of tectonic evolution,they will produce complex structural assemblage patterns.The single pre-existing faults control the complex "Y" type structural assemblage of the main faults,while the complex "X" type fault assemblage is easy to form if the pre-existing faults have opposite tendency and intersect each other on the sections.If there is no early fault control,it is easy to form stepped and compound half-graben structural assemblage patterns in structural belts 2 and 3 of Nanpu Sag.?The main faults controlling oil and gas migration in the study area are type II faults and type IV faults,in which type II faults can form effective oil only in complex structural styles or in places with small angle between strike and extension direction of the sag.Gas reservoirs,in addition to type IV faults,can also be an effective secondary migration channel for oil and gas when they stop developing vertically.