Argentine state-run oil company YPF said Tuesday that it had signed a memorandum of understanding for Malaysian energy company Petronas to invest in its massive Vaca Muerte shale formation.

Under the preliminary agreement, the companies would jointly develop a 187-square-kilometre (72-square-mile) swath of Vaca Muerta in the southern Patagonia region, YPF said in a statement.

YPF, which was nationalized in 2012 through a seizure of Repsol's majority stake in the company, has been seeking international partners to help it develop Vaca Muerta.

Vaca Muerta is considered one of the world's biggest known deposits of unconventional energy, with 661 billion barrels of oil and 1,181 trillion cubic feet of natural gas resources, according to YPF.

Follow us on Twitter: @ALB_Magazine.