For anyone still questioning whether the U.S. shale-oil boom is a historic reshaping of the U.S. energy market, today’s Energy Department report on domestic crude-oil stockpiles offers a striking statistic: The U.S. currently has more oil in storage than at any time since 1931. Commercial crude-oil stockpiles rose to by 3 million to 397.6 million barrels last week, the Energy Department said in its weekly Petroleum Status Report. Oil stockpiles are up 10% since the start of the year and 30% since May 2008. All that extra supply has kept U.S. oil prices under $100 a barrel even as prices...