KIEV, June 25 - U.S. oil major Chevron is expected to invest $25 billion in development of the Olesska shale gas deposits in Ukraine, Volodymyr Ihnashchenko, an advisor to the environment protection and natural resources minister, said Tuesday.

Ihnashchenko spoke in the Ivano-Frankivsk regional council seeking to persuade local lawmakers to approve production sharing agreement that would open way for Chevron to develop the deposits.