In a new revenue-raising measure, Venezuela’s energy ministry said Thursday that private oil companies operating in the country would have to convert to joint ventures with the government within six months. The energy minister, Rafael Ramírez, said at a press conference Thursday that the operating agreements would have to be swapped for ventures that are 51 percent state-owned and pay royalties of 30 percent. The fields in question produce roughly 500,000 barrels of oil a day of Venezuela’s total production of 2.6 million barrels a day.Full Story