Fracture system characteristics in naturally fractured carbonate reservoirs seem central to any development plan. In this article, a combination of outcrop studies, core studies, seismic, and borehole image logs were used to characterize natural fractures in a naturally fractured carbonate heavy oil field in Iran. A field study of fractures at the surface and in the sub-surface was conducted and regional tectonic fracture systems characterized. Three general orientations of mainly vertical and sub-vertical fractures were identified and characterized over the crestal area. Two main fracture sets, one shear conjugated and the other clearly a tensile fracture set, were identified. The frequent shear fractures resulted from compressional tectonics forces. This type of fracture is normally tight and impermeable but in this field they have largely been opened as the stress regime changed to a tensile tectonic regime by bending, accompanied by uplifting or drag folding, thus creating high-permeability fractures. Borehole image logs proved as useful tools in identification and characterization of natural fractures in the study area. Results obtained from this study can be implemented in optimizing well placement, reservoir simulation, hydraulic fracture design, and evaluation of the studied heavy oil field for appropriate production technology.