This week’s meeting of the world’s oil cartel will show how much its power has diminished amid sweeping changes in the global energy market. Oil prices have plummeted in the past eight months because of a half-decade surge in U.S. production and weak international demand. Brent crude for July delivery ended Friday near $65 a barrel on London’s ICE Futures exchange, far below the $100 needed by several members of the Organization of the Petroleum Exporting Countries to balance their budgets. In the past, OPEC forced prices higher by cutting production , or it steadied them by flooding the market during crisis, war or when it wanted to make a point about its collective might. The 12-country group’s meeting in Vienna on Friday is likely to result in a very different response: doing nothing. OPEC delegates expect the group to keep its current production ceiling of 30 million barrels […]