EFFECTS OF FRACTURES IN FOLD-RELATED FAULT ZONES

Conceptual models of fault zones include an increased density of fractures nearing fault surfaces. The interconnectedness of these fractures is critical to supporting fluid flow through fault zones. However, thrust fault zones may have additional fracturing patterns and permeability characteristics due to their common association with folding. As thrust zones are difficult to observe at the surface, these patterns can be measured on the outcrop scale and visualized through three-dimensional modeling. To quantify patterns in fracture connectedness and permeability, we study three thrust fault zones characterized by folding through field analysis and modeling. In the field, we observed many thrust faults and their respective fault zones, and we described, sketched, photographed, and measured the orientation of these zones. Hundreds of GPS-oriented detailed pictures were used to produce 3D outcrop models which were then transferred to Move, a structural geology modeling software. Move was used to map fractures, folds, and faults. By mapping fractures in 3D and 2D space, parameters were calculated to estimate connectivity and permeability changes laterally across the fault zone. We produce fracture density maps and graphically compare fracture density across the fault zones to show fracture density patterns across the folded hanging wall and the unfolded foot wall. The hanging walls show higher connectivity and permeability due to the increased fracture densities from folding. Lateral changes in permeability and connectivity that are created in fold-related fault zones may therefore enhance hydrocarbon and fluid migration, implying that these results may have industrial applications.