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General schematic of offshore wells similar to the BP Deep Horizon


I'm in the final stages of a long project this week so posting has been light. Here's quick review on the geometry of the actual bore hole in unfolding BP disaster which is currently being pumped full of drilling mud, the Top Kill, in hope of reducing or stopping the flow:

BP remained cautious about the outcome of the much anticipated "top kill" procedure, as did President Barack Obama, whose credibility stands to suffer if one of the country's worst environmental catastrophes does not end soon.

But the fact that the London-based energy giant was able to launch the complex maneuver around midday and keep it on track in the first hours was a welcome respite from a string of failures and setbacks in the 37 days since a rig blast triggered the disaster.

In the illustration below courtesy of Trees Full of Money, the well at the surface would probably be about 36 inches round, if it hasn’t been wallowed out by normal operations or the blow out. It would be topped with the blow out preventer (BOP). In this case a wrecked one.

The borehole goes down to about 18,000 feet. The hole will telescope as all wells do, from 36” across at the start to about 1000 feet. Then it would be reduce in diameter to somehtig smaller, like 18 inches, then 13 inches, then 10 inches, etc.

The diameter would eventually get down to 7-8 inches at the depth of the oil as normal drilling when at depth is usually 6-9 inches in diameter. We don’t have the actual Deep Horizon well plan so we can’t say for sure what the casing diameters are at various depths.

Two observations. One, the sediments on the surface of the ocean bottom in this region include rich Mississippi River deposits that go down for hundreds of feet. Setting off conventional explosions around or in the bore hole, as some have suggested, would cave those sediments in and close the hole. But friends of mine in the industry speculate that the loose sediment wouldn't have anywhere near the weight or tensile strength needed to keep the it shut.

Two, the greatest growth in oil production is coming from new wells in the offshore sector of the industry. If exploration and production in that sector are hindered for any length of time as a result of this catastrophe, it could come home to roost faster than anyone currently expects. Oil prices are likely to go up soon anyway, as the US and the world emerge from the current recession, and demand picks up (Recall that oil prices were surging past record highs just before the economic meltdown in 2008). The combination of increased demand and severe limits on offshore production could easily spell $5/gal gasoline or worse. As bad as the ecological effects and political criticism may be, 5 dollar a gallon gas will arguably cause even more damage to the economy and any incumbent politician than the original spill.

That's not to argue that we shouldn't insist on more stringent safeguards such as better testing of the Blow Out Preventers -- which appear to have failed here -- or better enforcement of existing safety standards already on the books. We obviously have to do that in the aftermath of this mess. But there smart ways and dumb, knee jerk ways to go about it. And there are consequences and trade offs in energy policy just like any other. Higher energy prices in return for increased offshore safety and beefed up enforcement are just one such exchange. At the risk of sounding cynical, my guess is that's a trade off the public won't like one bit.


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