The productivity of wells in fractured reservoirs depends, in terms of rate and sustainability, on the heterogeneity and variable connectivity of the open fracture network. Outcrop studies in Cretaceous carbonates from the Catalan Pyrenees illuminate this issue and reveal the degree of uncertainty associated with the interpretation of fracture data from wells and seismic. Three examples are chosen to provide verifiable data, parameters and concepts which can be applied to the workflow of fractured reservoir characterization. We discuss fracture properties and distributions in the subseismic volume, the coupled behaviour between litho-mechanical properties, in situ stress and fracturing, and the permeability properties of fault damage zones. The outcrops also highlight some of the difficulties involved in constructing static reservoir models and evaluating fracture interpretations derived from software-based techniques such as surface curvature.