Does Monterey sound death knell for US shale boom? By: CNBC.com News May 23, 2014 at 09:27 AM EDT The downgrade of California's oil reserves raises questions about the sustainability of the U.S. boom, which has sent production soaring to new highs. Read More >> Related Stocks: Chevron Corp Exxon Mobil iPath Dow Jones-Goldman Sachs Crude Oil Fund