ot apols - but I think many here will have thoughts about the BP oilwell leak. I don't claim the least expertise in such things - but if they dump tons of mud on top of the failed valves - will not the pressure of the escaping oil eventually erode that mud, and if it cannot, then it may effectively pressurize/saturate that area of the ocean bed beneath the mud? If so we could see a spectacular even bigger disaster with oil emerging from the mud periphery like some kind of "deepwater oil fountain"? Also, if the mud fails, perhaps it could then be well-nigh impossible to seal the leaks as they are even more inaccessible.
I believe that depositing the 'mud' is just the first stage, and once that is done and stabilised, then they will pour concrete (or cement) on top of the mud.
From my understanding, a problem could occur if there are 'weaknesses' in the area around the drill pipe itself - there would be no problem from the area around the well as the oil is prevented from escaping by the rock sea-bed.
Like you, I know nothing about the job and the above is only a précis of what I have read.
Yes, I'm sorry, but you have no expertise. I'd go further, and say 'no clue'. But don't feel bad about that. Neither does 99.999% of the media coverage :)
They are not planing on dumping tons of mud on top of the failed valves. They are planning to force the mud into the wellbore.
Do you want an actual explanation? Here's a drilling 101... It's taken me almost an hour to type this, so please give me the courtesey of reading it and understanding it ...
When an oil well is drilled into bare rock ( 'open hole' ), the hole is filled with a drilling fluid called 'mud'. This mud is pumped down through the centre of the drill string ( which is hollow ), and returned up the anulus. Continuous circulation.
The mud has several functions.
1) It cools the drill bit;
2) The circulation returns cuttings to the surface;
3) The density of the mud provides a hydrostatic head which prevents the formation pressure from 'blowing out' into the well-bore.
The 3rd is the most important here. The density of the mud column creates a hydrostatic head which is higher than formation pressure. The well is said to be 'over-ballanced'. This is what prevents formation fluid from entering the well in an un-controlled way.
Once the well is drilled, steel casing ( pipe )is run into it to line the well, and cement is pumped into the space between the casing and formation. This seals off the formation from the well-bore.
Once casing is set, the mud inside the casing is circulated out to a lighter completion fluid, like a brine. This is much lighter than mud. There is now a pressure differential between the outside of the casing and the inside. The cement and casing integrity hold it back. The well is now said to be 'under-ballanced'.
If this fails ( as it has done ) then high-pressure hydrocarbon enters the casing. Since the high-density mud has been circulated out to low-density brine, the hydrostatic column in the wellbore can no longer hold back the formation pressure, and we experience a well 'kick'.
If the well kicks at this stage, ( casing set ) then that's a serious problem. It's not meant to do that! We need to immediately circulate back to heavyweight mud, if possible.
At the sea bed ( at the top of the wellbore ), a series of very large valves called BOPs ( Blowout Preventers ) are connected to the top of the casing. These ought to close in emergency situations like this. These also failed. ( This is the major failure here. )
Now, we have uncontained hydrocarbon release to surface, and ( in this case ) consequent total loss of the rig. If the BOPs operated as designed, the total loss of the rig should have resulted in the BOPs 'failing safe', ie closing.
The design of the subsea BOPs is that they have very large hydraulic accumulators which store enough energy to close the rams and shut the well in in case of catastrophic failure,like loss of controll from the surface rig. This failed to work, and is the principal focus of investigation.
The leaks at the moment are coming from the marine riser ( the pipe that comes from the top of the subsea BOPS to the rig. ) The riser which was previously vertical and leading from the BOPS to the rig is now lying in a snotty heap on the sea-bed, and pissing out oil.
If the BOPs could be closed, we'd be OK. But for some reason, it can't.
AIUI, the current situation is that there is dril-pipe in-hole, through the open BOPs.
Now, the BOP has a couple of side-entry ports, called the 'kill' and 'choke' lines. I won't describe the normal function of these lines here.
What is being attempted it a 'top kill' , where we 'bull-head' ( ie force ) hi-density mud down these lines into the well-bore. We no longer have a circulation path, so we are just 'ramming' high-density fluid into the well-bore, from the top, to attempt to get back to the original over-ballanced drilling situation. ( Killing it. ) This will push the hydrocarbon fluid back into the formation. This is not easy. It gets easier as the mud is pumped down, and the surface pressure drops as the fluid column becomes more dense, holding back the formation.
The problem is that depending on the leak paths, attempts to bull-head may simply result in the pumped mud pissing out of the existing holes in the marine riser, rather than forcing on down the well and killing it.
Once the well is over-ballanced once again, then we have time to think.
I could go into *much* greater detail, but a public NG is not the place..
But honestly, the most experienced drilling engineers in the world are on the case right now. Ill-informed opinions from the general public and popular media are worthless. Totally worthless.
Indeed, that's one of the most informative narratives I've read, if a little tetchy at first!
To follow on from the idea that bull-heading may not work because no-one knows the exact leak paths I read somewhere that if the mud fails to do the job because it simply gets pushed out of the leak path they are planning to pump crap in the the form shredded tyres, golf balls, rope etc down with the mud in the hope that as they are forced out they will block the exit holes. I have to say that at the pressures involved that sounds optimistic but by the time they get to that stage I guess they'll be clutching at straws - as if they aren't already.
We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Andy Champ saying something like:
Indeed; an acquaintance of mine, fresh from uni with a geology ticket, got gainful employment looking after a tank of mud on a rig. Boring as hell, but paid tremendously more than anything else he could have done.
We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Ron Lowe saying something like:
Exactly, and Obama's posturings for public consumption don't help matters. Just where is he going to get the 'best people for this', oh wait, they're already there.
OK, here are mine - no doubt not practical or they would have been done:
I don't know how far below the seabed the oil lake is but presumably a pretty long way - a mile or something? So, get a pointy stick several thousand feet long, put an appropriately sized bomb on the end (or several of them along the length of the stick), shove the stick down the hole and detonate about halfway down, thereby collapsing the hole way below the seabed and sealing it off for good.
Alternatively, borrow from the medical field of angiography, and put an umbrella-like device on the tip of the pointy stick: shove the stick down the hole and open the umbrella (like the surgeon did when unclogging my dad's arteries).
Hey - you could even combine the two: umbrella device at the tip, then explosive charges higher up the stick as a failsafe or belt-and-braces. Brilliant. Red Adaire, eat your heart out.
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