Russia's last unalloted big oil fields a hard sell

* To be auctioned off on Dec.2

* Reserves estimated at 140.6 mln t

* State set out strict terms

MOSCOW, Aug 11 (Reuters) - Russia has finally set a date to auction off its last unalloted big oilfields, but analyst say the terms it set out for a potential buyer make the deposit difficult to use and develop.

Rosnedra, an agency responsible for monitoring licences, said on Tuesday that the Trebs and Titov oil and gas fields in the country’s northwest will be sold as a single lot on Dec. 2 with starting price tag put at 18.171 billion roubles ($605.7 million).

The deposits, located in Nenets region near the shore of the Arctic Ocean, are the largest unallotted hydrocarbon fields remaining in state reserves and attracted huge interest from oil companies.

India's state-run Oil and Natural Gas Corp ONGC.BO has proposed to Russian major Rosneft ROSN.MM that the two jointly bid for the fields with oil reserves estimated at 140.06 million tonnes.

LUKOIL LKOH.MM, Russia's second-largest crude producer; TNK-BP TNBPI.RTS, half-controlled by BP BP.L; Gazprom's GAZP.MM oil arm, Gazprom Neft; and Bashneft BANE.RTS, owned by Sistema AFKC.MM holding, expressed their interest in the fields.

But analysts believe that the terms of the ownership, including obligations to sell 15 percent of produced crude through the oil exchange and to refine 42 percent of crude produced, can spook off the potential buyers.

“The proposed terms complicate the project significantly.... Crude exports will primarily go through the Northern Sea route, while the bulk of the refining complex is located in the European part of Russia.,” VTB Capital analysts said in a note on Wednesday.

“With additional transportation costs implied, as well as the lack of exchange trading for crude oil, the economics of the project could suffer as a result of the conditions which have been imposed.

Uralsib analysts believe that due to these conditions, Russia’s largest oil producer, state-owned Rosneft, is a frontrunner in the tug-of-war for the fields.

“We believe that despite the conditions imposed, Rosneft still has a high chance to be successful, while other bidders may need to create a consortium to participate in the auction,” Uralsib analysts said in a note.

Reporting by Vladimir Soldatkin; editing by Lidia Kelly