BBC: The US is set to require oil companies to plug 3,500 non-producing Gulf of Mexico oil wells in an effort to prevent future leaks, officials say. The interior department will also require companies to dismantle 650 unused oil and gas platforms. Some installations have sat idle for decades without inspection for leaks. The order comes five months after an explosion at a BP oil rig in the Gulf of Mexico caused one of the worst environmental disasters in US …