So what is the idea of drilling relief wells? Isnt that what they are trying to do now? Relieve the pressure so the repairs can be made?
If they drill relief wells wont they be keeping the oil they get?
What a mess.
look at this, it's a bit old but completely relevant.
http://www.nola.com/news/gulf-oil-spill/index.ssf/2010/05/costly_time-consuming_test_of.htmlSpaces between pipes not closed off
Probert also presented Congress with a schematic of BP's cementing plan, which he repeatedly said his firm followed to a T. Although he never mentioned it in his written or verbal testimony, the drawing Probert attached to his prepared testimony May 11 shows what drilling experts say is a key design flaw that could easily have allowed a blast of natural gas to shoot to the surface undetected and destroy the rig before the crew of 126 knew what hit them.
oil-halliburton-cement-052010.jpgView full sizeThe graphic shows the wellhead 5,067 feet below the water's surface and the bottom of the well more than 13,000 feet below that. It diagrams how the drill pipes telescoped down in sections -- some about 2,000 feet long, some shorter and others longer.
With each section, one metal tube fits inside another, leaving a space called an "annulus" where heavy drilling mud can circulate and carry the drilled-out material back up to the surface. According to the diagram, one of the spaces between different-sized pipes was not closed off -- a no-no, according to some experts.
"It looks pretty on paper, but you can't accomplish that successfully and have a good cement job," said Tom McFarland, a cementing consultant from Marrero who has decades of experience cementing oil wells. "The chance of getting a good cement job on that is nil."
McFarland said the diagram indicates the space was completely open to the reservoir of oil the Deepwater Horizon had just tapped, and he is convinced that is why the well blew.
No O-ring seal depicted
McCormack, the University of Texas professor, isn't so sure that the blowout went through the annulus, rather than breaching the center of the well and blowing out the top. But either way, he was baffled by the diagram Halliburton gave to Congress. He was so surprised by the lack of an O-ring seal that he wondered if it was an error.
"There's a free path all the way to the top of the well bore. Normally you wouldn't do that," he said. "If the well was completed as designed, I think that would be an issue the way it's shown there."
A picture being worth a thousand words, here is the visual: edited - heres the link because the forum seems to be making this too smal to read.
http://media.nola.com/2010_gulf_oil_spill/photo/oil-halliburton-cement-052010jpg-e618a2271a66c847.jpg
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There is a full gap in the well bore where oil and gas is escaping 10000+feet under the seafloor.
As for your question, what is the idea of the relief wells?
The basic premise of sealing the well is to stop the flow and seal it in concrete. At 5000 feet under sea level (the seafloor) the pressure of the area is 2000 psi. At 17000 feet under the sea floor, near the area of the oil, the pressure is closer to 7000 psi. That oil is coming up and spraying like a sandblaster. The well drilling process has processes to equalize pressures, using the "mud". That mud is basically bentonite, the grey clay they use in sealing ponds or for fining wines. It's a heavy clay and with the assistance of pressure pumps they pump it down to meet the pressure of oil coming up. The idea is the balance the pressure - ie, 5000 psi pushing up and 5000 psi pushing down. This effectively stops the flow, once they achieve that they can pump in cement and concrete like materials to perm seal it. But they cant pump concrete into a gushing hole because it has to set and be stable. They have to balance pressure to do that.
They attempted to push mud in on the top via the "top kill" and all the mud just went right out the holes in the casing. Thats why it failed. The relief wells and the concept behind it is that they get underneath the portion of the well that is broken and begin pushing mud there. If they can balance the pressure, then they can seal it below the broken pipe and really seal it.
They are drilling two wells, and these reliefe wells have a target about the size of a dinner plate. they literally intersect into the existing pipe. once they penetrate, they begin pumping the mud to balance pressure.
Thats my understanding of the mechanics and what they are trying to do.
Topic: can someone explain (Read 10218 times)
