Motor ships of the type LENANEFT of two variants (projects R-77 and 621) are the big decker tankers of the "river-sea" class with double boards and double bottom, with machine compartment and superstructure in the rear part.
Project 621 is a modification strengthened for sea navigation and navigation in ice, which have increased size of hull, machine power and modern superstructure.
Motor ships of the project R-77 were built since 1972 in the USSR and since 1974 in Bulgaria; 46 units were built in Bulgaria. Motor ships of the project 621 were built since 1983 till 1997 in Bulgaria. Up to 32 units were built. Soviet-built ships were assigned serial numbers starting from one; bulgarian-built ships - numbers from 2001.
Motor ships of the type "Lenaneft" are the main tankers of the "river-sea" class of Lena Shipping Company. Ships are used for the northern delivery of fuel and also are operated in Volga basin, on Caspian, Black, Azov, Baltic seas, on seas of Far East. In 90-ties some ships were transferred from Sibir to european seas. Some ships were sold to different other shipping companies, including foreign ones, and registered under "comfortable" flags.