Characteristics Of The Mesozoic-Cenozoic Concave-Uplift Assemblage Structure And Fault-Rock Assemblage Structure In Hetao Basin

With the industrial oil and gas flow obtained in well Song5 and well Jihua 2 of Hetao Basin in2018,this area has become a hot area for oil and gas exploration.Structure is the basis of the formation and distribution of oil and gas reservoirs.Although a lot of previous studies have been carried out on the structure of Hetao Basin,the research on the structure closely related to oil and gas accumulation?the Concave-Uplift assemblages structure,the Fault-Rock assemblages?is not deep enough,which affects the further exploration.Based on the analysis and interpretation of the existing structural map of the key seismic reflectors and the two-dimensional seismic data,this paper divides and contrasts the present sag uplift composite structures of the Hetao Basin Te?Paleogene bottom?,Tn₁?Miocene bottom?,Tn₂?Pliocene bottom?,Tq?quaternary bottom?and the Paleogene bottom,Miocene bottom and Miocene top at the end of the Oligocene At the end of the Pliocene and the end of the Pliocene,the paleo sag and uplift composite structures of four major faults are analyzed,including the plane characteristics of the fault rock combination,the position of the fault rock layer,the structure of the fault plane,the relationship between the fault and the rock layers on both sides,and the activity of the fault,etc.and the relationship between the Song5 well and the Jihua 2x well and the Concave-Uplift assemblages structure and the Fault-Rock assemblages structure is analyzed and obtains the following understandings:?1?Starting from the lowest point of te reflector in the northeast of Taiyangmiao in the north,according to the combination of trough line,valley line,ridge line,uplift line and fault line,this paper divides the present sag uplift combination structure of Te?Paleogene bottom?seismic reflector in Hetao Basin.There are four types of Concave-Uplift assemblages structure,i.e.point concave side uplift type,point concave side uplift fault type,side concave side uplift type and side concave side uplift fault type Structure.According to the same method,the present Concave-Uplift assemblages of Tn₁?bottom of Miocene?,Tn₂?bottom of Pliocene?and Tq?bottom of Quaternary?in Hetao Basin are divided.Based on the Paleogene thickness map and the existing seismic data,the paleo sag uplift assemblages of Te reflector?Paleogene bottom?in the late Oligocene,the late Miocene and the late Pliocene are divided.In the same way,Tn₁and Tn₂ reflectors are divided into paleo Concave-Uplift assemblages.By comparing the present Concave-Uplift assemblages structure of Te,Tn₁ and Tn₂ seismic reflectors with the corresponding paleo Concave-Uplift assemblages structure,it is concluded that the present Concave-Uplift assemblages structure of each layer is roughly the same as the corresponding paleo Concave-Uplift assemblages structure,with only slight changes in the scope.?2?This paper analyzes the structural characteristics of the faults in Hangwu,Hanghou,Hanghou No.1,Hanghou No.2 faults in the basin from five aspects:the plane characteristics of the fault rock combination,the position of the fault rock layer,the structure of the fault plane,the occurrence relationship between the fault and the rock layers on both sides,and the activity of the fault.Hanghou and Hangwu faults are flat slope faults,Hanghou No.1 and Hanghou No.2faults are parallel slope faults;four major faults are all from Cretaceous system to the surface;Hangwu,Hanghou and Hanghou No.2 faults are mainly in the same dip half ridge half valley shape with the occurrence of the rock strata on both sides,Hanghou No.1 faults are mainly in the combination of reverse dip half ridge half valley shape and valley shape alternately from northeast to southwest;four faults are gradually renewed From the end of the Pliocene to the end of the Pliocene,they are all continuous active faults,and their amplitude of activity is increasing in the vertical direction.In the strike,they are less active at both ends of the fault and larger in the middle.?3?S5 well is located in the middle of the point concave side uplift type Concave-Uplift assemblages structure in Hangjinhouqi unit.Its Oligocene reservoir is developed in the valley like formation in the East footwall?ascending wall?of Hanghou No.2 fault.The Oligocene and lower Cretaceous source rocks are located in the ridge like formation in the West hanging wall?descending wall?of the fault.At the same time,Hanghou No.2 fault is also a Concave-Uplift assemblages structure of Shajintaohaidian point concave side uplift fault type.In S5 well,the fault continued to be active from Oligocene to Pliocene,and the active range increased gradually.JH2 well is located in the higher part of the structural unit of Xilinhuduge point concave side uplift fault type,and in the west is close to Langshan fault.?4?Based on the main achievements and understandings of predecessors on the control of oil and gas reservoir formation by the the Concave-Uplift assemblages structure of source rock and the Fault-Rock assemblages structure,as well as the relationship between the industrial oil and gas wells S5 and JH2 and the related the the Concave-Uplift assemblages structure of Lower Cretaceous and Oligocene source rock and the the Fault-Rock assemblages structure,it is preliminarily considered that the formation of Oligocene oil and gas reservoir of Song5 well is mainly related to Hanghou No.2 faults'the Fault-Rock assemblages structure.The formation of Cretaceous and Oligocene oil reservoirs in Jihua2 well is mainly related to the Concave-Uplift assemblages structure of Xilinhuduge point concave side uplift fault type.It is speculated that the ridge line of Linhe,Hangjinhouqi,Xilinhuduge,Shajintaohai the Concave-Uplift assemblages structural unit,the high section and valley formation of Fault-Rock assemblages structure related to Hangwu,Hanghou,Hanghou No.1 and Hanghou No.2 are favorable oil and gas accumulation areas.It is suggested to further explore these areas.