SINGAPORE, July 17 (Reuters) - Exports of light sweet Sokol and Vityaz crude from offshore Sakhalin Island in Russia will fall by a third to 5.69 million barrels in September due to scheduled maintenance, sources familiar with the matter said on Wednesday.
The reduction in supply coupled with robust demand in Asia have caused spot premiums for one of the grades Sokol to hit a 4-month high.
Sokol crude exports will fall to five 700,000-barrel cargoes in September, down from the usual seven, trade sources said. The export volume will return to normal in October, said a source with knowledge of the fields' production.
At Sakhalin 2, Vityaz crude exports will fall to three 730,000-barrel cargoes in September, one source said, while there could be up to four cargoes in October, down from the usual five cargoes every month.
The quality of Vityaz will also become lighter during the maintenance, sources said. Its API gravity will rise to 46-47 degrees, up from the usual 43-44 degrees, they said.
Sakhalin Energy, operator of Sakhalin 2, did not respond to requests for comment.
Sakhalin 2 includes the Piltun-Astokhskoye oil field and the Lunskoye gas field in the Sea of Okhotsk offshore Sakhalin Island in the Russian Far East.
Gazprom is the majority shareholder of Sakhalin Energy, followed by Royal Dutch Shell, Mitsui & Co and Mitsubishi Corp.
Sakhalin 1, operated by ExxonMobil Corp, is made up of the Chayvo, Odoptu, and Arkutun Dagi fields, located off the northeastern coast of Sakhalin Island.