UPDATE 1-Argentina's YPF and Chevron agree joint pilot project
* Accord paves way for shale investments in Argentina
* Recently nationalized YPF courting foreign energy firms
* Initial deal envisions drilling 100 wells at $1 bln cost
* Details on Chevron investment yet to be hashed out
Dec 19 (Reuters) - Argentine energy company YPF signed a partnership deal with U.S. oil major Chevron Corp on Wednesday that aims to pave the way for investment in the South American country's shale energy resources.
The details of a permanent deal will be negotiated over the next four months. The companies said Wednesday's letter of intent envisions an initial joint venture to drill 100 non-conventional oil wells at a cost of $1 billion.
YPF's chief executive, Miguel Galuccio, said earlier this month he expected his company to finalize a deal with Chevron, and another deal with Argentine company Bridas Holding, before the end of the year.
However, Galuccio and Ali Moshiri, Chevron's head of operations for Latin America and Africa, said the pact signed on Wednesday only covered a pilot phase.
"The question is going to be how big the investment is going to be beyond the pilot," Moshiri told reporters. "Our goal is to start as soon as possible. What we need is to push our teams to put a definitive agreement together as soon as possible."
The two executives said they aimed to come up with a permanent agreement on how to collaborate to develop part of Argentina's non-conventional energy resources at the vast Vaca Muerta site and boost oil output in the Neuquen basin.
Galuccio called the preliminary accord "a very important day for YPF."
YPF, which was nationalized in May, has said that to boost output it needs to invest more than $30 billion in the next five years, $4.5 billion of which is to come from strategic partners.
Spanish oil company Repsol has filed a U.S. lawsuit to block Chevron's partnership with YPF.
After Argentina seized control of Repsol's majority stake in YPF in April, Repsol threatened to file legal action against any company that partnered with the Argentine company.