Lacunarity analysis of fracture networks: Evidence for scale-dependent clustering

►Stratabound fractures are contained within distinct mechanical units and are regularly spaced while non-stratabound fractures, terminating randomly within the rock mass, are typically clustered. ►Lacunarity normalized to account for fracture abundance can quantify clustering in different fracture networks. ►Factures in the Devonian sandstone of Hornelen basin show an increase in clustering with a decrease in spatial scale. ►This reflects a gradual evolution from a “stratabound” system at the scale of sedimentary cycles (100-200 m) to a “non-stratabound” fracture system geometry at the finer 10's of meters thick bedding scale.