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Carbonate Fractures Controlled by Strike-Slip Faults: A Case Study in Tazhong Uplift, Tarim Basin, NW China

Abstract

Although fracture development along the fault zone is one of the effective ways of reservoir improvement and prior studies have confirmed fractures associated with faulting, studies on the understanding of the characteristics of fractures and kinematic mechanisms under the control of strike-slip faulting are few. Based on new three-dimensional high-resolution reflection seismic data, cores, slices, logs, and fluid inclusion, the tectonic fractures which are dominant in Tazhong Uplift, are mostly in the NE orientation and have a high fracture abundance near the NE trending strike-slip faults which have not been paid enough attention. The fractures formed in three tectonic events, coincident with the timing of NE-trending strike-slip faulting, the end of the Silurian, the end of the Permian, and the Tertiary respectively. Vertically, image logs show the smaller the distance to strike-slip faults, the greater the depth of fracture development. Areally, along the trend of the strike-slip faults, there is an inverse relationship between the fracture frequency and the distance from the NE trending strike-slip faults. The fracture frequency decreased sharply within 2.5 kilometres from the NE trending strike-slip faults, but further decreased slightly beyond 2.5 kilometres. Along the strike of the strike-slip faults, there could be subsection control on fracture development. Fractures in northern and southern sections are more developed than those in the middle section. In the northern section, the fractures on the western side of the NE trending strike-slip fault are more developed than those on the eastern side, while the opposite is the case in the southern section. We proposed a geometric model in which local left-lateral horizontal displacements and clockwise rotations of a local set of faults initially trending NS. The clockwise rotation resulted in gaps and overlaps, showing the high fracture abundance of northeast and southwest parts of fault blocks which could be the favourite targets.