Trump has promised to unleash domestic oil, gas, and coal production, largely by rescinding "job-killing" rules and environmental regulations, without detailing specific plans for the Energy Department and its nuclear-heavy policy portfolio. The United States held the spot as the world's largest oil producer for over two years - it was surpassed by Saudi Arabia in August - partly on the back of surging output from the Bakken formation in Heitkamp's state. Texas, meanwhile, is the largest U.S. pumper of crude oil and home to two of the country's largest petroleum refiners.