Chevron Corp. has an agreement to work with Argentina’s state-controlled oil company YPF SA on evaluating some sites for energy development.

In an email, Chevron spokesman Kurt Glaubitz confirmed Friday that his company and YPF had signed a memorandum of understanding to “explore areas of mutual interest on conventional and non-conventional opportunities.” He did not provide other specifics and declined additional comment. Financial terms were not disclosed.

YPF needs billions of dollars to go after unconventional oil and natural gas reserves. But major oil companies have held back from investing because Argentina has refused to pay the $10 billion that Spain’s Grupo Respol says it is owed after Argentina expropriated Repsol’s controlling stake in YPF in April.

Argentina also recently announced an elaborate system of price controls and said the government will decide what profits can be made by any energy company working in Argentina. The country has the world’s third largest shale reserves after China and the U.S.

Chevron, which is based in San Ramon, Calif., has had an on-going, collaborative relationship with YPF since the early 1990s.

Shares of Chevron rose 69 cents to end at $117.25. U.S.-traded shares of YPF, which is headquartered in Buenos Aires, fell 35 cents, or 2.7 percent, to end at $12.75.