Distribution of strike-slip fault-fracture volume and its controlling factors in the southwestern Ordos Basin

The fracture can improve the property of tight reservoir and benefits for petroleum accumulation in the Ordos Basin, but the distribution of the fracture related to the small-scale intrabasinal strike-slip faults is still unclear. Using variance and ant track attributes based on the 3D seismic data, combined with well logging, core and outcrop data, the distribution of fracture was analyzed in detail in this contribution. There are two sets of strike-slip faults trending NW and ENE in the southwest Ordos Basin. The fault-fracture volume consists of the faults and the dominant high angle fractures around the faults. The fault zone is characterized by the dominant fractured damage zone while the fault core is underdeveloped. The distribution pattern of the fault-fracture volume varies in the different layers. In the Upper Paleozoic-Triassic, fractures developed bandedly on both sides of the NW-trending fault. The fault-fracture volume has a greater width and higher density of fractures in this layer. In the Jurassic -Cretaceous, narrow fractured damage zones develop on both sides of the NW and ENE-trending faults. The fault-fracture volume has a lower density of fracture, and fractures develop heterogeneously along the faults. Over all, the distribution of the fault-fracture volume is controlled mainly by the activity intensity and arrangement of faults. The intense activity of faults leads to the superposition of the fractured damage zone and wide banded fault-fracture volume. The weak activity of the fault leads to the narrow width of single fault zone. On this occasion, fault- fracture volume develops at the bifurcation of horsetail splays, stepovers of en echelon linkages and intersections of faults locally. The distribution of fractures in the southwest Ordos Basin is an example to understand the mechanism of micro-fault in other craton blocks. It is also helpful to clarify a new exploration target, the fault-fracture reservoir, in the Mesozoic in the Ordos Basin. © 2024 China University of Mining and Technology. All rights reserved.