Natural-gas prices closed higher Thursday after a weekly stockpile report showed a smaller surplus than expected. The front-month September contract settled up 7.5 cents, or 2%, to $3.906 a million British thermal units on the New York Mercantile Exchange. It was the third-largest one-day percentage gain since late June. Producers added 78 billion cubic feet of gas to storage for the week ended Aug. 8, the U.S. Energy Information Administration said. The addition was 4 bcf smaller than what analysts and traders had expected. Natural gas for September delivery shot up 1.8% immediately after the update’s release. Power plants probably played a big role in the smaller-than-expected surplus by switching fuels to buy more gas, analysts said. Gas has dropped in price this summer, making it more competitive with coal for fuel, and some hotter weather has also created more demand for electricity to power […]