Discrete fracture network modelling of faulted and fractured Apulian platform carbonates (Altamura Formation, southern Italy)

This work focuses on the spacing and length distributions of bed-perpendicular fracture sets present within a carbonate multi-layer, and on their effect on the volumetric and hydraulic properties computed after DFN modelling. Results of the integrated field and laboratory analysis are consistent with an uneven spacing distribution of stratabound fracture sets due to, probably, their relative timing of formation. The oldest stratabound sets formed within individual limestone beds bounded by bed interfaces that acted as mechanical interfaces. Differently, the youngest stratabound fracture sets formed within smaller rock volumes also bounded by the pre-existing fractures. Non-stratabound fractures consist on sheared pre-existing fractures originally compartmentalized within individual beds and, hence, form incipient faults. DFN modelling of representative rock volumes show that both volumetric (P32 and porosity) and hydraulic properties (correspondent permeability) are not strongly affected by stratabound fractures, but by the two main sets of non-stratabound fractures. These two sets, characterized by strike-slip kinematics, likely form a pronounced structural anisotropy controlling the fluid flow within the fractured carbonate rocks.