Don’t expect a major ramp-up of oil production in Oklahoma’s hot new shale plays any time soon, even as companies invest billions of dollars in the region, said Newfield Exploration Co.’s chief executive officer. Producers need more exploration time and a higher oil price before they can begin accelerating drilling in the Scoop and Stack oil formation, Lee Boothby said in an interview in Oklahoma City Thursday. Newfield may eventually sell its Bakken Shale assets in North Dakota as one way of financing development, he said. Crude prices hovering around $50 aren’t high enough for explorers to start taking on the kind of debt they’d need to significantly speed up, Boothby said. It may be a year or two before companies learn enough about the Scoop and Stack’s underground geology to gear up production.