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Most carbonate rocks are characterized by high heterogeneity which implies changes in their vertical and lateral distribution, geometry and properties based on special aspects of their generation, depositional history, evolution and influence of exogenic processes. The oil-bearing carbonates of the Famenian in the study area tend to occur as complex reservoirs characterized by heterogeneous storage and flow potential. Diagenetic secondary changes resulted in various types of rocks differentiated by the configuration of the void space. The most extensive secondary changes evident to a greater or lesser degree in all the cored sections of the analyzed wells were caused by leaching which in its turn modified the carbonate fabrics and created heterogeneity. The configuration of the void space formed the foundation for the differentiation of petrophysical rock types. The findings obtained from the detailed lithological and petrophysical description of the Famenian rocks were used to group the identified reservoirs into the following classes based on the prevailing configuration of the void space, i.e. porous, vuggy-porous and fractured-vuggy-porous[1]. While the porosity values are comparable, the fractured-vuggy-porous type has the highest flow potential (maximum permeability values of the three types) due to leaching whereas the vuggy-porous type is characterized by average permeability and the porous one has the lowest flow potential (Figure 1). The type of the void space also predetermines the shape of the capillary pressure curve and respectively the pore throat radius distribution (Figures 2 and 3) as well as electrical and acoustic properties of the rocks.