Friday, May 28, 2010

Why the "Top Kill" won't work

When I worked for Pan American Oil Corporation in the late 1960s, one of the endless pastimes of the suits on the 4th floor was gaming worst case scenarios and how to deal with them: say if a salt dome ruptured, or a rogue gusher occurred. At the time, lots of new tracts were being developed in Plaqueminnes Parish, Louisiana, and the "big boys" were concerned about making some inroads, including into new offshore leases. One trouble -shooting problem that emerged confronted a well suddenly erupting on its own (say because of a gas or other explosion) and that couldn't be stopped. The remedy was a "top kill" - pumping mud or sediment into the well to halt the outward oil jets.

On another occasion, a guy named Denny, with a yen for futuristic scenarios (this way May, 1969) put this zinger forward: Imagine you're way offshore, drilling more than 15 miles out in the Gulf, and probing the sea floor one mile below the surface. You drill down more than 13,000' to tap a large reservoir. What do you do to prevent its rupture and polluting the whole damned Gulf?

None of the suits had an answer, and in fact, believed Denny mad, because in their view no such deep ocean drilling would ever occur, or if it did - ever be safe. One geophysicist who begged to solve Denny's conundrum - a guy named Dean Kring, laughed at first- then responded:

"You'd need back-up systems out the wazoo. You'd need at least three, maybe four levels and safety thresholds, and a final one to try to make sure some kind of 'dead man's switch' was activated. Something to shut the well down in the event of a blowout. I'd also make sure there's a reserve well tapped into the main, so if the worst happened, and the dead man's switch crapped out - at least the gushing oil could be siphoned off"

Dean's sketch solution is shown in the diagram. Needless to say, he was way way ahead of his time. The sort of basic reserve well he depicted is now common practice in nations like Norway, which also do deep water drilling. Yes, the cost is an extra bundle, but it provides an ultimate safety valve if say, the last trigger to activate the dead man switch (called an "acoustic trigger") decides to punk out.

Would anyone in that clique of oilmen have believed for one second that a "top kill" could stop a blown out deep water well, 1 mile down? No way in hell! The general consensus was that top kills were only useful for plugging rogue gushers on land, no one even considered it anyplace else.

At the depth of the Deep Horizon blowout, you're confronting pressures of 2,000 lbs. per square inch at every angle. If the aperture of the blown well hole is some 300 sq. inches, that means you are attempting to counter a pressure of at least 300,000 lbs. or 150 tons, per square foot. There is simply no material residue of the needed density - short of maybe cobalt - that could do the job and there is no known consistent force to apply it. If the mud is being injected at some 2000 gallons a minute, the maximum force supplied based on the volume of mud (assuming a density equal to silicon or maybe SiO2) is about ten thousand tons "positive" (given the water pressure as negative). More to the point, the differential pressure would be epxected to increase as one approached the actual blown hole.

To put it bluntly, there is no way the top kill will work - not in ten hours, and not in ten days. Even if by some magic a temporary stoppage is achieved this will not last, and will be followed (I predict within hours) by a mammoth new pressure blast and a much larger hole, possibly five to eight times the diameter of the existing one.

This means the only option is what ought to have been done ab initio - a reserve (relief) well, in fact probably two or more, drilled adacent to the Deep Horizon well hole to siphon off the gushing oil.

It's a pity that BP didn't learn or apply this reserve well until after the fact, which likely won't be before August.

What it does show, is that any deep water drilling in the future will absolutely have to have reserve wells in place before the main well is tapped. We cannot afford another Deep Horizon disaster.

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