Wednesday, May 12, 2010

Top Hat Dome on Seafloor, Relief Well 1 Ahead of Schedule

The second, smaller containment dome, "Top Hat" is on the seafloor, being prepared for placement over the gushing wellhead.
The "top hat," a 5-foot-tall, 4-foot-diameter structure, weighs less than 2 tons. The structure was deployed by the drill ship Enterprise.
BP built the smaller dome after a much larger, four-story containment vessel designed to cap the larger of two leaks in the well developed glitches Saturday. Ice-like hydrate crystals formed when gas combined with water and blocked the top of the dome, making it buoyant.

The new device would keep most of the water out at the beginning of the capping process and would allow engineers to pump in methanol to keep the hydrates from forming, said Doug Suttles, BP's chief operating officer for exploration and production. Methanol is a simple alcohol that can be used as an antifreeze. _CNN

Meanwhile, BP engineers retrieved the "brain" of the failed blowout preventer (BOP) and performed "brain surgery" to allow them to get an accurate read on the pressure at the well head. Next, they hope to perform the "top kill" or "junk shot" operation -- shoving rubber junk and matting through the BOP in an attempt to clog it, and stop the oil flow. They would then top the plug off with cement.
“We retrieved what is called the yellow pod, this is the sort of brain on the BOP, and brought it to the surface,” Suttles said...“We are currently working to re-wire that brain. We’re going to redeploy back on the BOP and we hope that will allow us to read pressures inside of it.”

...the supermajor is still canvassing other, alternative options. One of these may well be attempting a "junk shot" through Macondo's BOP stack. Taylor said that BP is pressing ahead with junk shot plans.

"We are still deciding on the right combination of materials," he said, adding: "We are getting lower pressure readings which has encouraged us to move forward with this 'top kill' option."

A junk shot involves injecting ground-up material, such as rubber, into the bottom of the BOP in an attempt to clog it. The material would travel upwards into the BOP, blocking it. Kill fluid and cement would then be injected into the well...

...Suttles said that BP has already manufactured the equipment it would need to inject cement and fluid into the well and it is being shipped to the location.

It is understood that BP has two cement skids already on Helix’s Q4000 semi-submersible platform, which is already on site to try to place a containment dome over the oil leak.

...A third option may be to shear the lower marine riser package and stab a new BOP on top of the existing one.

“That also is a very, very complicated task and also brings risks with it,” Suttles said. _Upstream

BP CEO was interviewed by Greta van Susteren last night:
Hayward: So we are now moving to deploy over the next 72 hours, a smaller containment device, a so-called top hat, which is described like that because it looks like a top hat, put in the water, on the end of a piece of drill pipe to fit over the leak. We'll be doing that over the next 72 hours.

In parallel there are a series of other operations being planned on the blow-out preventer, most importantly the so-called top kill or junk shot whereby we would pump into the blowout preventer material to clog it up and stop the flow...The issue is the quantity of gas and seawater in the large dome. That is a difficult combination. So, by moving to a smaller dome we'll have less seawater and, hopefully, a better chance of minimizing the hydrate formation and being able to get in sort of system to work.

...So Plan C is the so-called junk shot, top kill, where we connect two flexible hoses to the top of the blowout preventer and pump material to block up the blowout preventer.

Plan D is to remove what is called the riser with which is sitting above the blowout preventer and put in place another blowout preventer. There's a Plan E and a Plan F. So we are working through a whole series of options that are being developed and engineered in parallel and deploying them in time sequence. _FN

Meanwhile, the first relief well is proceeding ahead of schedule:
... the Transocean semi-submersible drilling rig Development Driller III is drilling ahead on the first of two relief wells planned for Macondo.

BP confirmed the well had reached 9000 feet on Saturday - its target depth is about 18,000 feet - adding the drilling was ahead of schedule. It did not provide an update on drilling depth.

Spokesman Mark Salt said that the Development Driller II is now on its way to Mississippi Canyon Block 252, and should arrive on location by the middle of the week.

Should the rig arrive on Wednesday, it is possible the second relief well could spud as soon as the weekend. _Upstream
BP had conservatively estimated that it would require 3 months to drill the relief wells, but if they are lucky they may cut that time in half.

Up until now, surface relief efforts -- booms, controlled burns, dispersants, etc. -- have been effective in keeping the bulk of the heaviest slick centered around the drill site. Peripheral drifts of slick have been significantly thinned to between a light slick and a thin sheen.

More coverage of oil spill from USA Today, NOLA, and Miami Herald

Cross posted to Al Fin



Blogger J. Paige said...

The site is the Times-Picayne newspaper. Best coverage I've found for this issue.

JP Straley

7:06 PM  

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