The Structural Evolution In The Cenozoic Of Subei Basin And Its Relationship With Oil And Gas

After nearly 50 years of exploration and research of the Subei Basin, We made a series of achievements in geophysics, sedimentary, construction and oil and gas side, there are some problems still exist:(1) Dynamic mechanism of basin is not clear; (2) There are several awareness about prototype basin types and evolution and so on.In this paper, Subei Basin as a prototype, According to today’s seismic and drilling data, to carry out seismic data interpretation, reconstruction current tectonic pattern.At the same time, it is based on the geodynamic background analysis, to restore and reshape the region in the Cenozoic tectonic framework and basin prototypes look different critical periods, and to explore differences in the tectonic evolution in the use of balanced cross section analysis in the main sectional of the area. Understanding made as follows:First, Clarifying the background of Basin dynamics of Subei BasinsEarly Cretaceous, the collision orogeny of lower Yangtze block and the periphery of orogenic belts laid the tectonic framework of the basin:South off the north and from west to east over the past constructed from NE to EW â†' NWW to arc spread. Late Cretaceous-Paleocene, the Pacific plate subducting beneath the Eurasian plate subduction angle increases, high angle latent within the Pacific plate and the mantle wedge did not rewind generated convection in vertical upwelling of features to make Europe crustal stretching east Asian continent gradually collapse-thinning, but due to the collision of the Indian plate and Eurasian plate, resulting in eastern China Zhang dextral SE-NW direction of twist.Second, to establish the structural framework Subei BasinSubei Basin cover portrait will be divided into tectonic fault bend layer rift tectonic layers Depression tectonic layers of tectonic subsidence interrupt further divided into two sub-structural layer. Each transverse depression have shown off to the south over the north rift graben feature, each axial depression and depression medieval settlement near the central axial line of each roughly the same. Subei Basin to Jianhu uplift apart, Dongtai depression and depression Yanfu depression showed right geese each line arrangement, especially in eastern Taiwan depression depression geese each line arrangement is most obvious.Third, improve the structural unit division Subei Basin, established type rift.Based on the extent of settlement and late reformation strength of rift period, the rift is divided into three kinds of structure types:rift type, fault-bend type and break- tilt type. Gaoyou Sag is rift type; break-Jinhu-. Qintong depression are fault-bend type; break-tilt type have a larger number, including Hongze, Haian, Yancheng, Lianshui, Funing, Baiju, such as depression. Overall Subei Basin was strike slip by Tanlu fault, break-tilt type have a larger number.Fourth, Clearly the characteristics of fault system and the control action to tectonicConsidering the scale faults, fault deformation formation,the basin can be divided into the basin cap detachment fault type faults, basement-involved type trunk faults and basement-involved type of faults and on the basis of three types. Most of basement-involved type main fault is the aid Indo-Yanshan regional thrust fault plane inverted displacement formed NE-NNE trending faults of Eocene rift depression or depression secondary functions to control the boundary fault effect.Basement-involved type trunk fault may extend to the deep crustal detachment fault deep connection chain extensional fault system constitutes a larger scale, or slip crustal scale crust formed in the weak layer detachment fault system.Fifth,established the times and the nature of tectonic evolution.Based on the basin cover internal angular unconformity and basin subsidence, faulting features can be divided into the Late Cretaceous Basin-III Quaternary basin, etc.-Paleocene, Eocene and Neogene. Late Cretaceous-Paleocene basin basement involvement in the development of a large number of small-displacement type normal faults, basin subsidence quickly and evenly, showing the crust evenly stretch forming rift depression, depression-depression type extensional basin off feature; Eocene basin the sub-basement faulting significant attenuation, and main fault intense activity, significant differences basin subsidence, block off the lifting movement obviously, trunk show inhomogeneous crustal rift caused by normal faults stretch, slip disc being faulted extension on the fault BASIN; Neogene-Quaternary faulting basically stopped, slow sedimentation basin as a whole, show after split heat depression basin subsidence stage features a cooling effect due to thermal lithosphere formation.Sixth, Clarify the tectonic evolution of the basinTaizhou-one deposition period of Funing group,The most elongation is in Hongze sag, followed is Gaoyou sag. Overall West and Central’s sags have relatively large elongation. Jinhu and Gaoyou sag have the largest deposition rate,and Haian and Yancheng sag is relatively small.Two-four deposition period of Funing group, The maximum elongation migrate to the site of the centers of each sag in Subei Basin, the maximum elongation rate is located in Gaoyou-Qintong sag, east and west sides’s elongation relatively reduced in each sag. Gaoyou Sag has the maximum deposition rate.Gaoyou sag has the maximum elongation in Dainan group, followed is Haian sag, and again is Hongze sag,Qintong sag. Gaoyou Sag has the maximum deposition rate.Gaoyou sag has the maximum elongation in Sanduo group, Gaoyou, Haian, Yancheng sag stretching effect is weakened in Basin.Seven, established a numerical simulation of tectonic stress fieldTaizhou-one deposition period of Funing group,Hongze sag has the strongest advocates stress intensity,followed by the Gaoyou sag, near the fault zone of Hongze sag has the maximum advocate stress intensity, it is the most obvious in the middle of the fault, advocates stress intensity high values of Gaoyou Sag mainly in the south of the sag,In Jinhu sag, high-value area focused on Jinhu-Baoying sag.Two-four deposition period of Funing group, Qintong,Gaoyou sag have the strongest advocates stress intensity, In Qintong sag,the high value areas are concentrated in the southwest,and presentat increasing trend from northeast to southwest. In Gaoyou sag, the high value areas mainly in the south of the sag, near the border of model region presents a high value is mainly noise boundary effects, belonging to an invalid value.Dainan group,Gaoyou sag has the strongest advocates stress intensity, Advocates stress intensity high values of Gaoyou Sag mainly in the south of the sag.Sanduo group, Hongze sag has the strongest advocates stress intensity, near the fault zone of Hongze sag has the maximum advocate stress intensity, it is the most obvious in the middle of the fault, Advocates stress intensity high values of Gaoyou Sag mainly in the south of the sag, In Jinhu sag, high-value area focused on Jinhu-Baoying sag.