Each of the block clusters were chosen for their vertical well performance, oil in place, shale rock quality and proximity of infrastructure, YPF told a small group of about 30 investors, bankers and analysts from the US and Brazil who took a trip this week to Vaca Muerta sites in Neuquen province.

The company also tipped data on the well results that contributed to the choices of the company, which has released scant exploration data since Argentina's government began the process to expropriate Spanish major Repsol's majority stake in April 2012.

"We're