Chinese oil-refining giant Sinopec and Russian leading oil company Rosneft have signed an agreement on the joint exploration and development of the Venin offshore deposit, part of the Sakhalin-3 project in Russia's far east region.

Under the accord, Rosneft will have a 74.9 percent stake and Sinopec 25.1 percent, the Itar-Tass news agency reported Thursday.

Reserves of the Venin deposit were estimated at 169.4 million tons of oil and 258.1 billion cubic meters of gas.

The Venin shelf in the Sea of Okhotsk covers an area of 5,300 square km, with six promising sites having been uncovered.

Rosneft and Sinopec signed an agreement on Aug. 30, 2005, on interim financing, and investment in the project amounted to 69.8 million U.S. dollars on Jan. 1, 2007.