Physical Analog Modeling Of Main Controlling Factors Of Strike-Slip Fault Formation And Evolution And Its Application

Strike-slip fault is an important structure in a petroliferous basin.The practice of oil and gas exploration shows that it is very difficult to accurately interpret strike-slip fault because of its difficult to determine displacement effectively and its varied profile style,and then affect the strike-slip fault reservoir control-reservoir control role.In order to explore the main controlling factors of the formation and evolution of strike-slip faults,physical simulation experiments of the formation and evolution process of the controlled variable single-factor strike-slip faults are designed by using the sandbox physical simulation experiment technique,this paper analyzes the influence of different factors on the formation and evolution of strikeslip faults,discusses the role of strike-slip faults in oil and gas reservoir formation,and guides oil and gas exploration related to strike-slip faults.A series of physical simulation analysis shows that the formation and evolution of strikeslip faults are mainly affected by five factors:first,the thickness of strata,which affects the development of echelon faults and the degree of strike-slip fault penetration;The thickness of strata is positively correlated with the scale and spacing of echelon faults,the width of fault zone and the strike-slip displacement needed for the through-connection of strike-slip fault zone,and negatively correlated with the number of faults.Second,the distribution relationship between strike-slip direction and fault strike-slip direction,which controls the tensional and compressive-torsional characteristics of strike-slip structures,makes it easier for the echelon-type faults to connect in the tensional environment than in the compressivetorsional environment,the width of the fault zone controlled by tension-torsion is relatively small,but the secondary faults in the zone are more developed,while the width of the fault zone controlled by compression-torsion is relatively large,but the degree of development of the secondary faults in the zone is low.Third,the fault subsection combination and connection mode,which controls the difference of the evolution of strike-slip fault subsection,forming "Down-sag" phenomenon,strain concentration and relatively strong fracture and reconstruction in the overlying area;In the overlying area,the strain is relatively dispersed,and the rupture and reconstruction in the overlying area is relatively weak,the "Flower-like structure" is an important indicator of the active stage of the strike-slip fault,the upper end of the flower-like structure can accurately identify the active stage,and the "Flower structure" is an indicator of the multi-period superimposed activity of the strike-slip fault,indirectly guide fine interpretation of strike-slip faults.Fifth,the intensity of activity affects the growth and connection of strike-slip faults under the same conditions.The larger the strike-slip displacement,the thicker the stratum can be penetrated.Based on a series of physical simulation experiments on the evolution process of strikeslip faults with different formation thicknesses,it is proposed that the ratio of maximum fault distance to fault extension length(D/L)of echelon faults gradually increases in the early stage of strike-slip,the D/L "Threshold" is about 0.015-0.016,which can be used to judge the penetrability of small-displacement strike-slip faults.The application of the D/L method to the analysis of the penetrability of the En-echelon strike-slip fault zone in the Bohai Bay Basin and the statistical data of the penetrable En-echelon faults in the Bohai Bay Basin have established the actual regional threshold of about 0.009-0.010,a new strike-slip fault-related trap area of 22.3 km2 was added in Shaleitian uplift and Liaodong Bay SAG.The strike-slip fault zones in the Shunbei region of the Tarim Basin are characterized by"Variable cross-sectional patterns and planar segmentation differences",which are combined with fine analysis of strike-slip faults and physical modeling of superimposed deformation,it is proposed that the formation and evolution of the northern segment of Shunbei 5 strike-slip fault is controlled by the "Stage-different direction" superimposed deformation mechanism,and the Middle Caledonian III is controlled by the difference of basement fault assemblage styles,in the late Hercynian collation,a series of En-echelon distributed normal faults were formed due to tensional torsion.The experiments show that the segmented overlaps of strikeslip faults increase the width of the fault zone and the range of the fractured reservoir.