Ukraine has signed a 50-year production-sharing deal with Chevron Corp. for shale gas exploration, Energy Minister Eduard Stavytsky said Tuesday. Under the deal, the American multinational energy firm will develop the potentially large Olesska shale gas deposit that stretches across Lvov and Ivano-Frankovsk regions in Ukraine's west. The Olesska deposit, with an estimated shale gas reserves of 0.8 to 1.5 trillion cubic meters, is expected to produce up to 10 billion cubic meters of gas annually. Kiev hopes Chevron will invest 10 billion U.S. dollars to develop the gas field. In the first phase of the project, Chevron is to invest 350 million dollars in exploratory works on the field to evaluate its investment attractiveness. Kiev picked Chevron as a partner to develop the Olesska field through a tender in May 2012.