Naphthides of perm deposits at Tatarstan territories: bitumen or oils?

Presented is a list of criteria for determination of naphthides types. Revi ewed are several approaches on naphthides classification, range of changes and average density values for four types of hydrocarbon systems. Presented are range of values and average values of some naphthides' parameters of m ain productive objects at Tatarstan oil fields.