U.S. producers of sand used to extract oil from shale are raising prices due to stronger demand, a sign higher oil prices are improving the outlook for the domestic fracking industry. U.S. shale oil companies, which pump sand into oil wells to make them more efficient, were ravaged by a 2014 global crude glut that hammered prices from more than $100 a barrel to near $26 in February 2016. Dozens fell into bankruptcy. However, publicly traded sand companies have pulled thousands of rail cars out of storage after oil hit a one-year high in October, thanks to rising demand, according to recent earnings calls and interviews. Sand companies idled half of the roughly 125,000 frac sand cars they had in service in 2014 after oil plunged, experts said, but nearly all are expected to return to service by 2018. Companies including Chesterland, Ohio-based Fairmount Santrol Holdings Inc; U.S. Silica […]