Brazilian producer Petrobras announced yesterday that the BOEMRE ordered a halt to the startup of its Chinook/Cascade deepwater floating production, storage, and offloading (FPSO) facility that had just been permitted a few weeks ago. The halt was ordered due to the failure of a buoyancy can that supports the free standing risers that bring oil and gas from subsea wells to the surface. The riser collapsed and sank in over 8,500 feet of water. The nature of the failure was not specifically disclosed, but is apparently serious enough to shut down the commissioning of the facility as investigations by Petrobras and the BOEMRE are begun.
A buoyancy can (seen at left) is a device attached to the top of a freestanding riser which is then anchored to the seafloor, keeping the riser in tension and in place. The bottom end of the riser is attached to a subsea well or production facility, and flows oil and gas to the FPSO through a series of hoses and connectors. FPSOs are the next step in deepwater production since these vessels not only process oil and gas, but can store the oil until offloaded to a tanker. This technique eliminates the need for oil pipelines far our into the Gulf.
We discussed free standing risers last summer during the Macondo well blowout when several were installed, but never used, to contain flow from the well. (Illustration from Recent Developments in Free Standing Riser Technology, Steve Hatton, John McGrail and David Walters from 2H Offshore Engineering Ltd. December, 2002)
You’re probably wondering why I’m writing about this seemingly obscure failure and subsequent work stoppage on the Petrobras FPSO facility, and why you should care. Here’s why you should care: freestanding risers are the backbone of the new subsea well containment systems that have been approved by the BOEMRE which are now required to get a deepwater drilling permit. The failure of a key component in freestanding riser technology raises the question about the reliability of the free standing risers in the well containment systems that are staged for rapid deployment in the event of another subsea well blowout. Having rushed the well containment systems into service so new drilling permits could be issued, one wonders whether they have been appropriately tested for durability and reliability. Like subsea wellheads, they are installed below the surface and are not visible except through the lens of an ROV camera. As the industry steps further and further out into deepwater, reliable riser systems will become key components in protecting the environment and making these projects economical.
We’ll be following this latest twist in the winding road back to the deepwater; it’s going to be critical to get free standing risers, just like capping stacks and subsea construction facilities, right this time, not only for the environment, but for the safety of those who work out in the deepwater.