Rock types that have been classified according to their petrophysical properties, especially properties that pertain to fluid behavior within the rock, such as porosity, capillary pressure, permeabilities, irreducible saturations or saturations. Petrophysical rock types are often calibrated from core and dynamic data, but are usually calculated from wireline logs, where possible, because the wireline logs are generally the only measurements that are available for all wells at all depths. Electrofacies approaches are often used to determine rock types from logs.