The Leiv Eiriksson, an oil drilling platform, is escorted by tugboats as it enters the Bosphorus in Istanbul December 31, 2009. The deep-water platform, one of the world's largest drilling rigs, passed through the Bosphorus Strait as it entered the Black Sea where Turkey and Brazil will carry out joint oil explorations. In April, state-owned petroleum companies, Turkey's TPAO and Brazil's Petrobras, signed an agreement to search for oil in the Black Sea. REUTERS/Murad Sezer (TURKEY - Tags: ENERGY TRANSPORT BUSINESS)