Tuesday, April 5, 2011

Petrobras in the GOM

There is a recent news item that should be a little disturbing to the public - if the public knew about it.

We all know that Petrobras was given a permit by BOEMRE to produce from their deep water lease (8,000' water depth) in the Gulf of Mexico. On April 3rd, it was reported that they had lost the riser buoyancy can on one of their wells. The 130 ton can floated off and the riser pipe collapsed to the sea bed causing damage to the subsea equipment. This link gives some pictures of how the risers are set up.

The incident should raise questions about the entire design - especially the connection of the buoyancy can to the riser. I will try to watch the BOEMRE web site for an accident report. That this should happen during calm seas raises serious concerns in my mind.

For background, the Petrobras FPSO is the first FPSO permitted in the Gulf of Mexico even though they are common elsewhere in the world. The ship , the BW Pioneer, was built in 1992 in a Japanese shipyard. It was converted to an FPSO by Keppel Shipyards in Singapore. It is a turret moored design which means the well flowlines enter into a common hub and the ship is allowed to "weathervane" around this hub or turret. In bad weather, they can lower the turret and the ship can leave the area under its own propulsion. The well connections are through a hybrid riser. The riser consists of a steel pipe held in tension by a buoyancy can. A flexible pipe connects the top of the riser to the turret. The FPSO will be operated for Petrobras by a contractor. The FPSO will be flagged in Bermuda.

Most folks in the industry hold a low opinion of Petrobras' safety record. While they are industry leaders in subsea technology, they tend to have a cavalier attitude and don't do their due diligence when using new technology. The sinking of the P-36 brought some of this to public attention. Here are my concerns:

  1. Not operated with Petrobras personnel but by contractors whose training, experience and commitment to safety may be open to question.

  2. Not flagged as a US vessel meaning it was not built to USCG requirements.

  3. Riser buoyancy can failure may mean the entire design is suspect.

  4. Petrobras reputation for short cutting safety issues.


Clay said...

If I recall, on P-36, one of the design scewups was putting a pressure vessel (I believe the slug catcher) INSIDE the hull. It blew up and compromised the hull. Whoops.

I've been a little concerned with the whole "drop the risers and run like hell when a hurricane comes" idea. The FPSO's are only built to withstand a 100-year WINTER storm. They'd be sitting ducks in a hurricane.

Anonymous said...

Your story is very true with exception to one small thing. Technically the collapse of the riser did NOT damage any well heads. The closest well head to the riser base location would be well over 16,000 ft away if my memory is correct. This was a lot of sub sea architecture damaged, just not any well heads. Like you say though, if one failed can the others fail as well?

Peripatetic Engineer said...

Anon - Noted! Thanks.

Clay said...

The subsea sled was crushed by the crumpled riser. That's a nice contract for the guys that made the first one.

Imagine receiving that call:
Vendor: "Hello."
PB: "Yeah, um, remember that subsea sled you made for us on Cascade Chinook."
Vendor: "Yeah, is it working well?"
PB: "Um, we need another."

They even had to wrangle the wild float can before it ran into another platform.

Still no word on why the chain let go.

Peripatetic Engineer said...

It seems BOEMRE doesn't feel this incident is important enough for an accident investigation. I do not see one listed on their web site. Anyone have any idea if anyone is investigating this?

Anonymous said...


Cascade/Chinook report