Doug Lucas stood outside a Houston energy conference early one morning last month handing out resumes and hoping to catch the eye of oil executives with a hand-written sign advertising “Petroleum Eng. Hungry for job interview.” Cut from oilfield services firm Halliburton Co in 2015, the 26-year-old temporarily turned to lawn care and cable-TV sales jobs while finishing a master’s degree in petroleum engineering at the University of Southern California. Despite relying on a depression-era sign for introductions, he is hopeful demand for petroleum professionals will come back. “It’s way better now than it was six or eight months ago,” he said optimistically, as he solicited business cards from convention goers. […]