Tectonic characteristics and formation mechanisms of strike-slip faults in the Western Siberian Basin, Russia

The Western Siberian Basin is an oil and gas basin with the greatest reserves and the highest production in Russia, and there is a large number of strike-slip faults. However, there are still many controversies about the tectonic characteristics and formation mechanisms of those strike-slip faults. Based on high-resolution 3D seismic data, this paper discusses the kinematic formation mechanisms of the strike-slip faults in the Western Siberian Basin after analyzing their geometric and kinematic characteristics. The following research results are obtained. First, the NW trending dextral strike-slip fault and the NE trending sinistral strike-slip fault are dominant types of strike-slip faults in the study area. The acute angle between two groups of strike-slip faults is about 84° on average, and the angle bisector corresponds to the north-south direction. The en-echelon faults intersect with the main displacement zone at 45° and are basically distributed in the near north-south direction. Second, there is horizontal movement and vertical movement in the Western Siberian Basin, overall with the north-south compression horizontal movement as the dominant one. In nature, strike-slip faults are dominated by compressive shear, the magnitude of strike-slip displacement is not significant, and complex local tectonic stress combinations may occur at the end and intersection areas of faults. Third, the uplifts developed in the north of the Western Siberian Basin are mainly near equiaxed uplifts (domes), with the NW trending strike-slip fault as the dominant, while those developed in the south of the basin are mainly elongated (non equiaxed) uplifts, with NW trending and NE trending conjugate faults developed. In conclusion, the formation mechanism of strike-slip faults in the Western Siberian Basin is a pure shear mode, which simultaneously achieves compression and tension in mutually orthogonal horizontal sections. The various associated structures and displacement zones result from the release of two stable shear stress fields developed in the sedimentary basins of the Northern Hemisphere. What's more, shear deformation sectors are formed under the condition of pure shear movement model. One or another edge of the deformation sector is activated to form the tail wing in the shear region, which provides conditions for different tectonic activation phases of tail orthogonal mesh along the maximum positive stress axes in different (orthogonal) directions. © 2024 Natural Gas Industry Journal Agency. All rights reserved.