Reply #6: The analogy would be stepping on the hose

[Kurt_and_Hunter]

Shoveling silt into the oil hole would be futile because the oil pressure would blow out the silt as you shoveled it in.

But smashing rock (below the ocean floor) is a different matter.

The pressure involved is high by human standards but mild by geologic standards. For instance, the pressure from oil wells doesn't erode the surrounding rock in the manner of a dam-break. If it did then all oil wells would become gaping holes. We usually have more trouble keeping the holes open than closing them.

But where I agree with you that pressure is probably a big part of the problem is the practical side of things.

The oil pressure may well make it almost impossible to deliver charges into the existing drill hole below the surface -- the oil would be pushing out whatever explosive device you tried to insinuate into the hole.