The Genetic Mechanism Of Strike-Slip Structure And Its Control On The Deep Natural Gas In Xujiaweizi Fault Depression

On the base of 3D seismic data, with Xujiaweizi fault depression as target, dressing systemly the distribute characteristics of different strikes of faults, arrangement mode, overstep pattern and displacement slip mode, thus space combination style of strike slip structures were analyzed. Then, combining with the fault throw backstripping method, based on the fault throw-distance profile and the characteristics of strata thickness of ancient basins, the genetic Mechanism and evolution process of strike-slip structure in Xujiaweizi depression will be discussed. Then build the Xujiaweizi fault depression evolution dynamics model. Last, from basin controlling, source controlling, reservoir controlling and hydrocarbon accumulating, we can set the control function of strike slip faults act on deep basin gas accumulation.The strike-slip structure pattern in Xujiaweizi fault depression are composed of right step en echelon arrangement Xuzhong-Xudong strike slip deformation zones caused by strike slip deformation. Due to the different overstep pattern, displacement slip mode and the development degree, the main strike-slip faults form various bends and overstep modes; For a main displacement zone, right-lateral strike-slip faulting forms five associate secondary faults, each of them distributes around with the main displacement zone with different angles, arrangement mode and displacement slip mode. Part of them composite to form the north and south of Xuxi faults.Base on boundary condition and whether exist pre-existing structures, three strike-slip structure genetic mechanisms of intraplate are summarized. They are “active” strike-slip deformation mechanism, “passive” strike-slip deformation mechanism and “transfer” strike-slip deformation mechanism. The Xujiaweizi fault depression is influenced by Xu zhong-Xu dong continuous right lateral strike-slip deformation as a whole. During the deposition of Huoshiling Formation, it is controlled by simple shearing mode active strike-slip deformation mechanism; During the deposition of Shahezi Formation, its deformation controlled by both strike-slip deformation and extensional deformation; During the deposition of Yingchengzu Formation, continuous right-lateral active strike-slip deformation mechanism control the deep magma to erupt out of the surface forming volcanic institutions. In the period of depression and inversion, strike-slip deformation are controlled by oblique extending and oblique compressing pre-existing faults formed in fault depression stage passive strike-slip deformation mechanism respectively.The petroleum geological significance of strike-slip tectonic deformations in Xujiaweizi fault depression during each stage of the evolution process can summarized as: a. the Huoshiling Formation’s active strike-slip deformation controlled the initial basin formation; b. the Shahezi formation strike slip-extensional deformation controlled the development and distribution of coal-bearing source rocks; c. the Yingcheng formation’s continued right-lateral active strike-slip deformation controlled the activities of volcanic edifices and the reservoirs distribution. d. In the depression phase, transtentional deformation makes pre-existing strikeslip faults re-active, they become the gas source faults to control the volcanic gas migrate and accumulate in accumulation period, instructing the distribute of the primary gas volcanic rock. e. In the reverse phase, the degree of transpression is weak, but some strike-slip faults still active, even cut into volcanic gas reservoir to be the adjust migration pathways, indicating the distribute of secondary gas reservoirs.