Depositional influences on fracture stratigraphy of a grain-rich carbonate toe-of-slope, Permian Bell Canyon Formation, West Texas, USA

Outcrop studies are essential for characterizing fractured carbonate systems, as they provide the most comprehensive understanding of how vertical and lateral facies variability and associated diagenetic events affect fracture network geometry and, thus, fluid flow in the subsurface. Outcrop analog studies on carbonate platforms and basins have revealed relationships between fracture size and depositional geometries to define fracture stratigraphy frameworks; however, studies on carbonate slope to toe-of-slope settings are sparse. This study constrains the fracture stratigraphy along depositional strike and dip in the grainstone and rudstone-dominated Pinery Member of the Permian-aged Bell Canyon Formation, Texas, USA. Fractures exhibit northwest/southeast and east-northeast/west-southwest strike orientations. In the proximal toe-of-slope setting, very thick-bedded upslope-shingling carbonate debrites exhibit compensational stacking with downslope-dipping carbonate turbidite complexes. The proximal debrite complex contains opening-mode (Mode I) throughgoing fracture networks that form a single mechanical unit. The distal toe-of-slope is organized into a weakly confined interbedded grainstone turbidite complex with a higher abundance of intrabed and bed-bound fractures. Fractures at this location form a positive linear correlation with bed thickness and form multiple vertically stacked mechanical units. Overall, fracture heights range from 0.01 m to 12 m with a median of 0.64 m, and fracture-set distributions are best characterized by truncated power-law or exponential distributions. Results of this study have implications for predicting facies- and tectonics-controlled fracture network geometries in the subsurface for oil and gas, enhanced geothermal, and groundwater reservoir characterization.