U.S. explorers added rigs for 19th week to highest since 2015 OPEC and allies agreed to prolong output curbs for nine months Oil traded below $50 a barrel after OPEC underwhelmed investors with its production-cut extension deal. Futures fell 0.4 percent in New York. Prices closed 1.1 percent lower last week after OPEC agreed to extend limits on crude output through the first quarter of 2018. Saudi Arabia’s Energy Minister Khalid Al-Falih said the oil-cuts strategy is working and that global stockpiles will drop faster in the third quarter. U.S. explorers added two rigs last week to 722, the highest level since April 2015, Baker Hughes Inc. said Friday. “It’s huge inventories around the globe that are really keeping a lid on prices, combined with the ability of those agile U.S. producers who scramble back into action should the oil price rise,” Michael McCarthy, chief market strategist at CMC […]