If the riser is removed and they can get to the top flange why would you not place another BOP on top of what they have? I can see not doing it before because removing the bent riser lets more oil escape, but why not now?
Two if you ran drill pipe into the BOP now, assuming it is open, could you run it to a good depth or would you get so much back flow every time you connected a stand that it would be imposable? If you could run it in, pumping mud at a few thousand feet would be far better than the Top Kill idea, even though you would lose a hell of a lot of it.
(Please, no 50000 gigabyte .PDF files!)
If the DP has dropped back down into the well, what they can do then, even if they don't have 100% seal on the wellhead, is to rig a snubbing unit at surface and run 1" wash pipe into the new riser and down into the surface casing and pump kill mud (18 pounds/gallon should do it).
Problem is, they've probably got multiple flowpaths from the formation face to surface: one up the old DP, one in the production string around the DP (what's left of it), and another behind pipe up through one of the liner laps into the production-casing/surface casing annulus to surface, which is how the gas got to surface in the first place.
They would sequentially have to fill all three of those flowpaths with heavy kill mud.
Oh, and there's also the problem that they're still communicated behind pipe with the lost-circulation zone above 12,000' MD, which stands ready to take their kill mud the same way it took their mud originally when they lost circulation at TD. Which would compromise their new hydrostatic regime they're trying to set up and allow the well to flow behind pipe again.
It's sort of a hydrodynamic version of whack-a-mole. Whack this one, the other one pops up. Gas has too many flowpaths to surface, it's gonna bite you.
They cut off the top of the riser. There is no way to bolt a BOP Stack onto that. There has been a failure inside the BOP Stack. The Engineers know this and this is why they will not run drill pipe inside the 9-5/8 inch casing which in all probability they could not anyway. The failure in all probability is at the casing hanger for the 9-5/8 inch casing. The oil and gas is coming from the formation around the outside of the 9-5/8 inch casing. You could fill the casing up with cement and the well would still flow!
That well will flow until the relief wells are drilled into the production zone and they kill the well and fill it with cement. Hopefully BPs effort to attach the new riser assembly will collect the oil until they have killed the well.
I pretty much agree with LG’s analysis on this. Too many problems all at the same time. they might have trouble killing this thing from the bottom in fact.
As to putting a new BOP on top of the one already in place, I think they are afraid that the integrity of the topside well structure has been compromised too much for that. Remember that 5000’ of riser and the deepwater horizon itself were anchored to that pivot point for two days before and during the sinking. That well head has withstood many extreme loads already and, if it were me making the decisions, I sure wouldn’t want to put any more stress on it at this point.
The question is one of whether or not there is junk in the hole. It'd be a real bugger to get stuck in there with the well blowing out--and there would be significantly less ability to capture the oil coming out.
Then there's the mud. If they needed 16.8# to hold it with the mile of riser, they'd need somewhere between 19# to 22# to hold it without a riser (5,000 ft. less column), and anything short of bottom would take heavier yet. Pretty tough to kill it halfway down...even with the ECD, and you'd lose the mud without a way to capture it at the wellhead.