Discrete Fractures Network (DFN) of the faulted Upper Cretaceous platform carbonates outcropping in the Pontrelli Quarry (Altamura Formation, Murge, Italy)

A representative volume of an area of 250x350 meters exposing Upper Cretaceous platform carbonates crosscut by two conjugate strike-slip faults is modeled using the software MOVE. The obtained DFN model is used to compute fracture porosity, and relative permeability distribution, within the carbonate rock mass. The aim of this work is to decipher the contribution of fault-related deformation on reservoir-scale fluid flow. The study carbonates crop out in a quarry of the Murge area, Italy, and correspond to an excellent analogue of the hydrocarbon reservoirs currently exploited in southern Italy. The outcrops expose a well-layered limestone affected by both background (diffuse) and fault-related (localized) deformation. Background deformation is made up of two orthogonal sets of joints striking N30E and N120E, respectively. The fault-related deformation is represented by two strike-slip fault zones trending N120E (dextral) and N160E (sinistral), which solve amounts of offset above seismic resolution (about 20m). Smaller faults pertaining to the two sets are present within the fault damage zones and surrounding rock volumes. In order to construct the DFN model, focused on the role exerted by the fault damage zones on fluid flow, we first calculated the spatial and dimensional parameters of background and fault-related fractures (orientation, density, length, aperture and aspect ratio) by mean of scan line and scan area surveys conducted in the field. Then, after statistical analysis of the field data, cumulative frequency distributions and scaling relationships among different fracture attributes have been computed. Finally, the overall permeability tensor of the representative volume was obtained by upscaling of DFN models on the basis of Darcy’s Law and laminar flow between parallel plates. The achieved results might be used for fluid flow simulations in fractured and faulted carbonates reservoirs at seismic resolution scale.