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From: Craig Jungers <crjungers_at_gmail.com>
subject: [Paddlewise] How many ways was I wrong about the Deepwater Horizon
Date: Tue, 18 May 2010 10:48:01 -0700
1. It's dynamically positioned not anchored. When the story broke the name
of the rig wasn't mentioned but its location was so I looked at Transocean's
web site to see if I could figure out what rig it was and it seemed to me
that it said it was an anchored rig out there. Either the web site changed
or I was looking at the wrong rig. Since it was dynamically positioned they
could have conceivable driven the rig off the well... if they could have
disconnected the BOP. As it was the rig was more or less permanently
connected to the BOP and the blow out directed right up the riser into the
rig feeding the fire.

2. The cement job was to temporarily close in the well pending production. I
was under the impression that they were still drilling and had just cemented
in the casing. It seems unlikely that 18000 feet of cement would blow out so
I thought that the well may have blown out through the substrate. Instead it
just blew out (apparently) as they were trying to set the third (and,
apparently, last) cement plug after evacuating all the mud from the well. My
original impression was that the substrate around the casing had failed when
the cement blew and that oil/gas would be coming up through the sea floor.
The descriptions of several "leaks" was what led me wrong. These "leaks"
turned out to be coming from several ruptured portions of the riser laying
on the ocean floor but still connected to the BOP.

3. I figured that the driller would notice reduced weight on the string or
the mud engineer would see a huge increase in mud caused by the bubble of
oil/gas coming up the well (and expanding as it rose). But they had
apparently evacuated all the mud from the well before setting the third
cement plug so no one knew there was a gas/oil bubble coming up from by that
means. And by the time the bubble had blow past the two cement plugs below
the one they were working on there was no time to see reduced weight on the
drill string.

4. I assumed that the falling riser and drill string damaged the BOP to the
point where it would not close. It now appears that there was no
communications with the BOP. The only way to close the BOP would be to
trigger the accumulators to pneumatically drive the rams in; I still don't
understand why the ROVs couldn't do that down at the BOP itself. It also
never occured to me that known damage to the annulus (a soft rubber bladder
that can be expanded to close off the well) would have been ignored. This
bladder was apparently used to determine what the pressure inside the well
was but may have been leaking... this would have caused them to see a lower
pressure than what was actually down-hole. If they thought there was lower
pressure this would have mad them believe that the cement slugs they were
setting would hold. Higher pressure could blow past the slugs once the mud
was evacuated (the weight of the mud holds the pressure inside the well).

In my defense I can only say that the lack of information and/or abundance
of misinformation or partial information was what led me astray.

Who knows what more will come out in this story.


Craig
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