The world's largest oil and gas company said it will invest up to $300 mil in a joint venture with Russia's state-owned Rosneft to explore the Russian Arctic shelf. The pact is part of a larger, long-term agreement they signed in Aug. '11. Rosneft will own 51% and provide personnel and access to its 23 sites in western Siberia. Exxon Mobil (XOM) will provide money, expertise and personnel. Drilling begins in '13 and they hope to begin production in '15. Exxon Mobil shares rose 0.7% to 88.60.