Here’s a link to Pravda suggesting that the Deepwater Horizon spill could be sealed by an underwater nuclear explosion and stating that just such an intervention occurred on September 30, 1966 to extinguish a gas well fire at Urt Bulak at a depth of 6000 meters below the surface.  Not sure that the cost-benefit of this makes sense… .  See http://www.kp.ru/daily/24482/640124/ .