Why Billions in Proven Shale Oil Reserves Suddenly Became Unproven
U.S. companies erased more than 20 percent of inventories Regulator examined estimates as wells lingered on books Ultra Petroleum Corp. was a shale success story. A former penny stock that made the big leagues, it was worth almost $15 billion at its 2012 peak. Then came the bust. Almost half of Ultra’s reserves were erased