By Adam Wilmoth Energy Editor awilmoth@oklahoman.comDomestic oil prices briefly topped $50 a barrel Thursday as the industry shows more signs of recovery from an oil price drop that has stretched for nearly two years. Despite recent gains, however, record U.S. and global oil storage levels continue to hold prices well below levels seen two years ago. "Because of increased efficiency, even marginal firms without much more of an increase in price will be viable and could turn some positive cash flow," said Robert Dauffenbach, director of the University of Oklahoma's Center for Economic and Management Research.Read more on NewsOK.com