Seabed collapse ? The well is 15,000 ft under the seabed.
There was a technique of using a special dynamite (gives off tremendous heat) to melt/collapse the casing/bore way down the hole in a series of staggered explosions, apparently used by Red Adair for one, could be all those who knew how to do it got laid off in the last decade or so.
Not heard it mentioned at all.
Seeing FredZarguna’s post, maybe it was considered after all.