BP's dome stopped by the very same substance that caused the accident: Methane Hydrates....

[Junkdrawer]

Biloxi, Mississippi (CNN) -- The effort to place a massive containment dome over a gushing underwater wellhead in the Gulf of Mexico was dealt a setback when a large volume of hydrates -- icelike crystals that form when gas combines with water -- accumulated inside the vessel, a BP official said Saturday.

The dome was moved off to the side of the wellhead and is resting on the seabed while crews work to overcome the challenge, a process expected to take at least two days, BP's chief operations officer Doug Suttles said.

Suttles declined to call it a failed operation but said "What we attempted to do last night didn't work."

Suttles said the gas hydrates are lighter than water and, as a result, made the dome buoyant. The crystals also blocked the top of the dome, which would prevent

...

http://www.cnn.com/2010/US/05/08/gulf.oil.spill/index.html?hpt=T1

Methane Hydrates are now suspected as the primary cause of the accident:

The deadly blowout of an oil rig in the Gulf of Mexico was triggered by a bubble of methane gas that escaped from the well and shot up the drill column, expanding quickly as it burst through several seals and barriers before exploding, according to interviews with rig workers conducted during BP's internal investigation.

While the cause of the explosion is still under investigation, the sequence of events described in the interviews provides the most detailed account of the April 20 blast that killed 11 workers and touched off the underwater gusher that has poured more than 3 million gallons of crude into the Gulf.

...

Based on the interviews, Bea believes that the workers set and then tested a cement seal at the bottom of the well. Then they reduced the pressure in the drill column and attempted to set a second seal below the sea floor. A chemical reaction caused by the setting cement created heat and a gas bubble which destroyed the seal.

Deep beneath the seafloor, methane is in a slushy, crystalline form. Deep sea oil drillers often encounter pockets of methane crystals as they dig into the earth.

...

http://www.chron.com/disp/story.mpl/ap/top/all/6995867.html

Scarecrow at FireDogLake called it last week:

What More Can Halliburton Tell Us About the Horizon Oil Blowout and Its Risks?

A publicly available Halliburton PowerPoint presentation from last November might tell us a lot about what could have caused the oil blowout, fire and massive oil gushing at the Horizon rig.

Suppose you’re that division of Halliburton that has the dangerous job of "cementing" the drilling hole and the gaps between the hole and pipe. You’ve done this lots of times in shallow water wells, but you’ve learned through previous experience in deep water there’s a particularly difficult problem having to do with the presence of gas that has seeped to the ocean floor and been captured in essentially "frozen" crystallized formations.

The problem is that when you drill into these formations, and then try to inject cement into the hole/gaps to prevent leakage, the curing process for that creates heat. That heat can, if not controlled, cause the gas to escape the frozen crystals. If a lot of gas is released all at once, as could happen during the cement/curing process, it can cause a blowout where the cementing is occurring, or force gas and/or oil up the pipeline to the drilling rig on the surface. And the heat created by the process may be just enough to ignite the gas , causing the explosion and fire.

Did this happen at the Horizon rig? And if Halliburton already knew about this problem months (years) ago, and knew the risks it might create, why are we just now learning about this?

From Halliburton’s presentation (large pdf), page 10, last November (my bold):

Challenges

• Shallow water flow may occur during or after cement job
• Under water blow out has happened
• Gas flow may occur after a cement job in deepwater environments that contain major hydrate zones.
• Destabilization of hydrates after the cement job is confirmed by downhole cameras.
• The gas flow could slow down in hours to days if the de- stabilization is not severe.
• However, the consequences could be more severe in worse cases.

....

http://seminal.firedoglake.com/diary/44349

[SidDithers]

1. K&R...

facts are good.

Sid

[damntexdem]

3. Yes, facts are good, but this reality is not good.

The corporate drill-baby-drill imperative has led to cutting edge technological activities that encounter over-that-edge problems that may be beyond our technical capacity to address adequately. Let's hope that in this case we are lucky and the problems are "solved" temporarily -- giving us a chance to learn about what we were doing. And just how much damage will be done in the meantime, even if we are lucky?

[csziggy]

2. K&R

[Gin]

4. were they shutting this well down by sealing it with cement?

this is a big producer...why seal it?

[madokie]

7. sealing the pipe to the ground

[Igel]

8. Not just sealing the pipe to the ground.

Sealing it so that it can be used for production later.

You drill lots of wells. Some don't work out. Some do. But you don't have production rigs at every drill site, you don't lay the pipe to pump the oil to shore or a convenient location "just in case", etc., etc. Or perhaps they just wanted to seal it off until prices went over $100/barrel. Who knows?

[jimlup]

5. Oh No

this problem isn't resolvable by any means I can think of.

[tekisui]

6. Bad to worse.