Current data on the composition, structure and formation routes of various petroleum hydrocarbons have been reviewed. The issues of stereochemistry and relative thermodynamic stability of hydrocarbons of various structures contained in oils, as well as some issues of origin and chemical evolution of petroleum hydrocarbons, are covered. Particular attention is paid to biometric hydrocarbons and hydrocarbons of a diamond-like structure. New data on modeling of oil formation processes are presented. Geochemical (genetic) typing of oils and condensates of various oil and gas provinces of Russia was carried out. Critical evaluation of applied hydrocarbon parameters and Rock-Eval pyrolysis data at correlation in oil-oil and oil-dispersed organic matter systems of rocks is given. Specific examples of non-use of methods of organic geochemistry of hydrocarbons in oil and gas exploration and oil and gas field (reservoir) geochemistry are presented.