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

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