Once the caisson was in position, the pile would be pumped out and driven into the ooze.

ECONOMIST: Fixing oil wells

The caisson could not simply be capped, because the oil pressure would blow its suction pile out of the sea floor.

ECONOMIST: Fixing oil wells

To make an oil-collecting caisson, such a pile would be used as a collar around a funnel-topped tube that would sit over the leak.

ECONOMIST: Fixing oil wells

Various sizes of caisson will be built, including one 15 metres (50 feet) or so in diameter, large enough to fit over a whole blowout preventer.

ECONOMIST: Fixing oil wells

The caisson would fill with oil from the leak.

ECONOMIST: Fixing oil wells

Whether or not a caisson was used, the oil from the containment assembly would then pass through a manifold a sort of switching yard for pipes to one or more floating risers leading to the surface and held vertical by buoys.

ECONOMIST: Fixing oil wells