I would drop a large inverted cone made of steel or concrete so that it's point obscured the breach. The weight of the plug would keep the oil pressure from pushing it out, while a stabilizing float attached to it's top would prevent the cone from tipping over. Like so:
| < Line up to deploying ship
O
O < Stabilizing float
|
----- < Steel/concrete plug
\ /
__\ /__ < Breach
V
Once it settled you could likely pour a block of cement around it...