Christopher Brownfield in the NYT:
This means more than simply “blowing it up”: it means drilling a hole parallel to the leaking well and lowering charges to form an explosive column.
Upon detonating several tons of explosives, a pressure wave of hundreds of thousands of pounds per square inch would spread outward in the same way that light spreads from a tubular fluorescent bulb, evenly and far. Such a sidelong explosion would implode the oil well upstream of the leak by crushing it under a layer of impermeable rock, much as stepping on a garden hose stops the stream of water.
It’s true that the primary blast of a conventional explosion is less effective underwater than on land because of the intense back-pressure that muffles the shock wave. But as a submariner who studied the detonation of torpedoes, I learned that an underwater explosion also creates rapid follow-on shockwaves. In this case, the expansion and collapse of explosive gases inside the hole would act like a hydraulic jackhammer, further pulverizing the rock.
