Structural characteristics, formation & evolution and genetic mechanisms of strike-slip faults in the Tarim Basin

Exploration and development practices prove that intracratonic strike-slip faults control the development of carbonate reservoirs and the enrichment of oil and gas in the Tarim Basin. Intracratonic strike-slip faults are characterized by short displacement, small throw and great burial depth, so there are still many controversies on their structural evolution and formation mechanisms. In order to settle these controversies, this paper firstly analyzes the geometric and kinematic characteristics of the intracratonic strike-slip faults in the central Tarim Basin. Then, based on extensive high-accuracy 3D seismic data and 2D seismic data, the formation and evolution process of the intracratonic strike-slip faults in the Tarim Basin are discussed deeply, and their genetic mechanisms are explored. And the following research results are obtained. First, the strike-slip faults in the study area have the characteristics of vertical stratification, plane zonation and segmentation along the strike. Second, the movement direction of the deep transpressional strike-slip fault is simple. The NE and NNE strike-slip faults are sinistral, and the NNW strike-slip faults are dextral. However, the shallow transtensional faults are more different in the movement direction. The strike-slip faults have a displacement of 400-1 500 m, and they are classified as intracratonic strike-slip fault with a small slip distance. Third, strike-slip faults were formed in the middle Caledonian, and some faults were reactivated in the late Caledonian-early Hercynian, late Hercynian, and Yanshanian-early Himalayan. The distribution of faults is different in different periods. Fourth, the formation of the strike-slip faults in the middle Caledonian is controlled by the basement heterogeneity and the compression action from the closure and subduction of the Proto-Tethys Ocean. The transtensional faults are R-shear branch faults or tensile break faults generated by the later activation of middle Caledonian strike-slip faults, and their formation is controlled by the subduction and closure of ocean basins around the basins in different periods. In conclusion, the structural characteristics, formation & evolution and genetic mechanisms of intracratonic strike-slip faults are in close relation to oil and gas, where great benefit of oil and gas exploration and development is achieved. Besides the Tarim Basin, the Sichuan Basin and the Ordos Basin have similar geological and structural settings, so the studies on typical basins will surely enrich and complete the theories on the intracratonic strike-slip faults in domestic micro landblocks and multi-cycle basins and point out the direction for the discovery of more oil and gas resource. © 2021, Natural Gas Industry Journal Agency. All right reserved.