Thursday, September 2, 2010

Deepwater Oil Spill - stack off, but another incident

Once again I am indebted to MoonofA, who is giving a more detailed hour by hour report, of some of the incidents that I miss. Fairly rapidly on Thursday afternoon, the team of ROV’s and surface vessels moved forward with the removal of the existing infrastructure over the Deepwater Horizon well, with the intent of replacing it all with a functioning blowout preventer from the 2nd relief well (which now looks to be no longer necessary at all). One of the first steps was to move the methanol feed (used to dissolve and remove hydrates from the internal structures of the stack) down from the rams of the top stack to feed into the original BOP. This was used to ensure that the different parts of the stack, such as the rams, were able to function, when needed. And now, I presume, the hope is that it will similarly ensure that the BOP rams can function if needed.

Removing the line from the stack


Replacing line on the BOP

Once the feed line had been moved, then the Enterprise came in and lowered the latching device that has been floating just above the stack for the past few days. It did not take long (and by doing so did not convey the difficulty) to drop the cap over the top end of the stack, and not long thereafter the stack was released and lifted away from the underlying transition and the original BOP.

Approaching the stack

The more interesting part of the exercise will come when they start to lift the original BOP and the transition spool. There are a number of different scenarios that have been proposed, depending on what happens, and why, as the first lift begins. If they can lift the BOP with the underlying drill pipe (DP) still attached, then they appear ready to grab hold of the DP after the BOP has risen a short distance, and cut it off. This will make it easier to get the BOP to the surface, and means that a more conventional fishing tool can be used to capture, and bring up the remaining length of the DP. Toolpush, for example, mentions some of the options available.

Sliding into place

The capping stack was released at about 4:30 pm Central, whereupon Admiral Allen issued the following statementz:
"Under the direction of the federal science team and U.S. government engineers, BP has completed the capping stack removal procedure – an important step in the process to remove and preserve the damaged BOP. This procedure was undertaken in accordance with specific conditions I set forth in a directive authorizing the capping stack removal and BOP replacement last week. BP will continue to follow these required conditions for the BOP removal procedure, which is expected to commence this evening. I will continue to provide updates as necessary."
One of the problems with the feeds from the Q4000 is that they are not time-stamped, so that it is hard to know if the latest glance at the feed below the moon pool, which shows that the pipe hasn’t moved since I last looked, is current or not.

The other significant news today was of the fire on the Mariner Energy platform in the Vermillion block of the Gulf of Mexico. The fire now appears out and there was apparently no leakage from the wells that were connected to the platform. The platform is in 340 ft of water, and was fed by 7 wells collectively supplying 1,400 bd of oil and 9.2 mcf of natural gas, that is now shut in.

I note that they were apparently waterblasting the rig and repainting it. One of the things to be careful of in those cases is the static electric charge that can build up in water vapor around the operation. From the Coast Guard report:


However, at this time, that is just conjecture, and we will have to see what the investigation reveals.

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