May 03, 2010

To contain a deepwater offshore oil leak, the leak must be sealed off below the leak and the wellhead must be capped or otherwise closed off as soon as possible. Only after the submarine leak is capped can the surface oil slick be properly dealt with. Anything less is pulling individual raindrops out of a hurricane -- and even that little at a short- and long-term cost to the environment almost as heavy as the oil itself.

(Then again, the end effect of the Deepwater Horizon spill must also be measured against the pre-existing 22,000 square kilometre dead zone reaching out into the Gulf of Mexico from the mouth of the Mississippi river: which had already been impacting the shrimp fishing industry to the east.)

The first (and only) line of pre-emptive defense is the blowout preventer: a method which has not been substantially updated since 1922. Should it fail, the only remaining action which can make a substantive difference is to slant-drill a relief well into the reservoir, then use it to pump in seawater and concrete to permanently close the well. Some countries have tried to require such a relief well to be drilled before mining the main reservoir. Until now, the counter-argument has always been cost.

No technology for repairing this kind of damage has ever been tested at anything like these depths. Even basic subsea oil recovery systems have only ever been previously used in shallow water less than 100 metres deep. We are deep into experimental territory here.

In shallow water, a relief well has been drilled in as little as thirty days under optimal conditions. Under the Gulf of Mexico, all drilling will be through hard shale rock, so conditions are far from optimal even without taking deepsea pressures into account. It is much more likely that drilling a successful relief well will take multiple attempts, if the water and oil pressures involved in deepsea drilling allow drilling a relief well at all.

Once again, our determination to delve ever further for new riches (resources, knowledge) has exceeded our known ability to mitigate the potential harm.

"Ah, but a man's reach should exceed his grasp,
Or what's a heaven for?"

- Robert Browning, "Andrea del Sarto"

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