The main factors in evaluating carbonate reservoirs are lithofacies, pore types, shelf setting, sequence stratigraphy, and diagenetic overprint. Several patterns are evident based on a review of carbonate reservoirs from around the world. First, dolomites, grainstones, and boundstones are the most common carbonate reservoir rock types, but any carbonate lithofacies can be modified by diagenesis to form porous rock. Second, secondary pore types tend to dominate carbonate reservoir facies, as opposed to primary pore types. Third, inner shelf, outer shelf, and slope lithofacies belts are prime exploration fairways that are relatively predictable, with middle shelf prospects being less so. Fourth, sequence stratigraphy describes the shelf-building and basin-filling pattern of carbonate sediments and provides useful models for exploration and production. Finally, carbonate sediments are subjected to two main types of diagenetic overprinting: steady subsidence into deep burial realms of diagenesis or subsidence interrupted by one or more periods of uplift and associated porosity-producing diagenetic reactions.