BUENOS AIRES, Dec 28 (Reuters) - Argentina'sstate-controlled energy company YPF hasreached a deal for Bridas Holding to invest in the country'svast Vaca Muerta shale resources, two industry sources said onFriday. Bridas Holding's owner Carlos Bulgheroni, an Argentine oilmogul, told Reuters earlier this month his company wasconsidering making a substantial investment in partnership withYPF. A day later, YPF's CEO said he hoped to finalize thefarm-in arrangement before the end of the year. No one in Bridas could immediately be reached to comment,and a YPF spokesman declined to comment. YPF has called a newsconference for 5:30 p.m. local time (2030 GMT). YPF says it needs to invest over $30 billion in the nextfive years, $4.5 billion of which is to come from strategicpartners, to help pay to develop Argentina's shale oil and gasresources. Finalizing a deal with Bridas would be the first majorinvestment accord signed by YPF since May, when Argentina'sleft-leaning government seized a majority stake in the companyfrom Spanish oil firm Repsol. YPF signed a letter of intent for a pilot partnership withU.S. oil major Chevron Corp on Dec. 19 that aims to pavethe way for major future investment in shale oil resources. In 2010, YPF announced the discovery of the mammoth VacaMuerta ("Dead Cow") formation in southern Argentina, whichcontains an estimated 23 billion barrels of oil equivalent. Bridas Corp, half owned by Bridas Holding and half byChina's CNOOC, holds 40 percent of Argentina's PanAmerican Energy. The remaining 60 percent is held by BP.