Here’s another one. If they can get the riser cut off, why not insert a tapered section of pipe, with a valve on it,(left open during insertion) into the BOV and just jam the thing in intil it seals. Then turn the valve off and complete the piping up to the drill rig?
OK, I think I see what they are doing. Looks like they are just trying to remove a small section of the small pipe. Should be off soon.