Be ready for up to one third of the U.S. shale industry to get knocked out, warns Texan billionaire Ross Perot Jr. The son of legendary oil magnate Henry Ross Perot Sr. said the recent U.S. shale gas boom was "unsustainable," and now it's time for a bust. He predicts that crude oil prices could go below $40 per barrel, which would shut down 20% to 30% of U.S. shale industry as the declining price makes production too expensive.