sounds idiotic to me

Obama has it under control. No worries.

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can only assume they are afraid plugging the "little" hole will burst something and create an even bigger and harder to plug hole.

an why plug it, why not get the oil to the surface and start production, it might as well start making money to pay for all the damage it's already done

-Lasse

A blow-out? There is a big column of fluid moving at high speed, block it suddenly and all sorts of interesting things are going to happen.

As I understand it, the risk being considered here is that closing down the valves too far (or too quickly) could raise pressures enough to cause an underground rupture in the existing well pipe. This would then cause oil to start erupting from the sea-floor at some distance away from the existing blowout protector, making it even harder to capture, and possibly increasing the total amount of oil escaping from the damaged well. That could be a worst-case situation, in that we could lose the ability to contain the oil via the existing blowout preventer and the new cap, *and* increase the total amount of oil leaking into the gulf.

Ideally, both the new cap and the existing pipe structure would be strong enough to hold back the full worst-case pressure of the crude coming up from below. If this turns out to be the case, then they can (carefully!) close the valves, choke the flow down to nothing, and there will be little or no oil leaking, and no need to pipe any up to the surface to be reclaimed or flared off.

The middle case would be one in which there's some risk of blowing out the damaged pipe if the valves are shut off entirely. In order to avoid this, a hybrid strategy would be needed - some of the valves would be closed entirely, and others would remain open but connected to pipes going to the oil-recovery ships on the surface. In this scenario, leakage into the gulf would drop close to zero, and the amount of oil flowing through the damaged well would be substantially reduced (with almost all of it being successfully tapped up into the ships on the surface).

What I believe they're trying to do, by being cautious, is figure out whether the third (middle) case is the way that they're going to have to do it, or whether they can go to the best-case (close all the valves and cap the flow entirely). Somebody in the .gov feels that it's preferable to delay the closure attempt by a few days (accepting a larger leakage into the gulf for that time), rather than risk an overpressure event which might rupture the wellhead and thus guarantee un-controlled worst-case leakage until the relief wells are completed (several weeks from now at least).

Sounds like they might be the ones that are afraid of math that you have been so desperate to find all these years.

Nice, except that you should have to pay me to wear and use your shtuff.

Exactly. AFAIK the not-so-optimal cement job has allowed the pipe inside the sandy sea bed to move about and possibly become damaged or at least fatigued, and then there is the question about whether the quality of the casing was sufficient to begin with.

What I don't get is why such questions weren't pondered before this new cap was designed and being fabricated. I mean, that hasn't happened overnight.

On a sunny day (Wed, 14 Jul 2010 12:48:19 -0700) it happened John Larkin wrote in :

I think the point is that if you stop >6000 pounds of pressure, the oil, if the well is weak, may find an other way out, so to speak make a new hole in the ground next to that blowout preventor.

They tried that, first thing. The problem is, at this depth, when methane mixes with water it forms methane ice, which gunks up all the collectors and hoses.

So the requirement is to capture the oil before it can mix with sea water. At 15,000 PSI or whatever.

John

Then close the valves slowly. If they even cut the flow by 1/3, it's better than 100% flow.

And why do baseline seismic studies now, when the problem is three months old?

Sounds like more politics to me.

John

Is 100% of the oil spilling out?

You've got a teeny pipe going into a great big oil deposit, and the pipe is set into ocean floor that's not made of very strong stuff. Furthermore, the pipe isn't set into the ocean floor very well -- one of the scandalettes that's flying around is that BP saved money by only putting in something like 1/5 of the number of reinforcement structures that their own engineering staff recommended.

What folks are _really_ worried about now is not so much that the pipe itself will rupture, but that the stuff the pipe is set into will start to crack open. Should that happen then you'll get a flow rate that'll dwarf what we've got now.

That's what you've got to lose.

My limited understanding is; the new cap has three valves, two of them are more on/off and the third can be shut a little at a time. That's what I gleaned from Thad Allen's last press conference. They will shut one and see what the pressure readings are. That will give them some info about the integrity of the well caseing. There in lies the rub. Say the pressure was at 7,850 lbs/sqin and in 6 hrs it went down to 7,300lbs/sqin. What does that mean? If it went to 3,000 lbs/sqin they know they have a problem. I the caseing is perforated and it's 1 mile under the earth, probably not a big concern, but if it's

So, I think they're thinking. MikeK

Well, in that case, they shouldn't close any of the valves at all, ever. Too big a risk.

John

They just started thinking now?

John

Oh great, you don't know how much I am relieved! Now where is that damn air freshener ?

Jamie..

It's obvious they maybe more concerned, not being able to tap that spicket afterwards, wouldn't you say?

If there are ten thousand Archis, all posting on Usenet and living in their Mom's basements, get told by Mom to get a JOB and *one* percent of them actually get out of bed and do it, how many are still left posting verbal diarhoe?

Answer: NONE...they were all the SAME person.

mike

Which raises the question of when the thing was operational, how the f*ck was it able to hold back the forces while it operated for months at less than 'full flow'? How is it suddenly so much more vulnerable downstream from the wellhead?

Sounds like dancing to stretch out the 'standing around doing nothing status quo' until the relief wells get drilled and tapped into.