Characteristics And Formation Mechanism Of Faults In Binchang Area,Southwestern Ordos Basin

Fault structure controls hydrocarbon accumulation,so it is of great significance to clarify fault characteristics and formation mechanism for hydrocarbon accumulation.Binchang area is located in the southwest of Ordos Basin,at the junction of Weibei uplift,Yishan slope and Tianhuan depression.It is in the transition region between the strong deformation of the basin margin and the weak deformation of the basin interior,and its internal faults are relatively developed.In order to further clarify the features and formation mechanism of the fracture in the study area,on the basis of the data collection and literature research,through the high precision 3D seismic resolution,the fracture of tectonic style in the studied area,and analysis the characteristic plane,in order to describe the fracture geometry characteristics of the study area,restore fracture tectonic evolution process in the study area,at the same time,Under the constraints of regional tectonic background and dynamic environment,the fault periods in the study area were divided,the relationship between different periods of fault activity was analyzed,the genetic mechanism of fault in the study area was discussed,and the evolution model was established.The results show that:(1)There are three groups of faults with NE,NW and NNE strike in the study area.The faults show the combination styles of echelon,feather echelon and parallel in plane.In the section,the occurrence is steep,the fault distance is small,with the structure style of erectus,negative flower and so on.(2)In Paleozoic,the caledonian hercynian tectonic movement was dominated by nearly S-N compression.The faults in the study area were mainly in echelon type in plane,and the NW and NNE trending faults cut the NE trending faults.In section,the occurrence was high and steep with strike-slip properties.In the early Mesozoic,the Indosinian movement mainly occurred in the NE-SW direction.The faults in the study area were linear and discontinuous in plane,and the NNE trending faults cut through the NE trending faults,while the NNE trending faults did not cut through the NE-trending faults.In section,the occurrence was steep and negative flower-like structure was developed.During the middle-late Yan Shan movement of Mesozoic and Cenozoic Himalayan movement,NE-SW extrusion stress is given priority to,the fracture in the study area in the plane is linear,NW and NNE to fracture,fracture has not been cut through the NE to occurrence on the profile is upright,main negative flower strike-slip tectonic development,area of the existing extrusion structure.(3)The NE trending faults in the study area are controlled by NE trending basement faults in the basin.The NW and NE trending faults were formed in the Caledonian period.The NW and NE trending faults appeared as conjugate faults,and the NE trending faults formed in the near S-N tectonic stress field during the Caledonian Movement.Since the Paleozoic,three groups of different strike faults in the study area have undergone multiple periods of tectonic activities and have obvious characteristics of succession development.(4)Combined with the data analysis of key Wells,the high production Wells of Chang 8 member of Yanchang Formation are mainly concentrated in sand body development area and near faults,and the oil and gas migration is affected by mudstone thickness and fault distance between Chang 7 and Chang 8 member of Yanchang Formation.