Industrial opportunism for the sake of nature

The lattice framework construction of the Bullwinkle platform was prefabricated on land and towed into the Gulf of Mexico in 1988. 4. Plugging

After the platform has been prepared, the well must be plugged and secured. There are different methods of abandonment to choose from, all of which require a correct placement of plugs to ensure pressure resistance.

5. Removing of the conductor and its cases

First, conductor cases must be taken out from the seafloor. Different methods can be used to do this, such as detonation or cutting. After this, cases must be divided into segments of 40 feet each to enable transportation to the shore. Cases are loaded by crane into boats and then offloaded in a port. The last destination for the cases is the disposal yard.

6. Platform removal

Only when the well is plugged and the conductor case is removed, can the platform be transported to the shore. The top and bottom sections are usually decommissioned separately, since there are different elements to each of them. If the top is transported in one lift, a derrick barge with sufficient lifting capacity is needed. Usually though this applies only to smaller platforms. For larger platforms, the top section can be separated into several modules so that a derrick barge can lift it. One can also cut the structure into smaller pieces which can be lifted with smaller cranes. Although using smaller cranes costs less, it requires much more time as a procedure.

The most expensive step however is removing the lower part of the platform. This can be done through the use of explosives, mechanical cutting, abrasing or other methods. The cutline should be 15 feet below the mudline. Once it is done, the jacket can be attached to the lifting equipment and transported to the shore. For objects taller than 200 feet, a derrick barge might be required.

7. Removing cables and pipelines

After the platform is taken away, all cables and pipelines should also be removed. Before this happens, however, pipelines should be flushed with the water and plugged. After this, they must be buried 3 feet beneath the ocean floor.

8. Site clearance and material disposal

Finally, platform parts transported to the shore can be recycled, refurbished and reused in other platforms. The site should be inspected to make sure that nothing is left behind which could present an obstacle for other uses. Any environmental damages should be documented.

Top: A short-eared owl rests on a North Sea oil rig mid-migration. Photo by: Kevin Duffy

Middle: Seals resting on a platform in the Caspian Sea.

Bottom: Marine life accumulated at the oil rig in California. Photo by: Joe Platko

Inhabitants of the platforms

Different species have been observed on platform structures. Some use platforms as a resting area or a pitstop, while others settle and live on platforms for their entire lives. Some species inhabit the underwater parts of the platforms, others inhabit the sections at the surface, and some reside on the structures above the water.

Underwater species: the majority of platforms host marine life formed around their steel jackets for years. One of the reasons for this is a low electric current which runs through the foundation, used to protect platforms against corrosion. Minerals dissolved in the water accumulate on the steel jacket’s surface and build a good foundation for corals. The corals then create a suitable habitat for fish and other marine species. In other words, with a single element (a steel jacket under a low current) a whole sea-life ecosystem is created. On average, the exploitation time of the rig (usually around twenty years or more) is enough to create a small marine life settlement of its own.

Sea surface species: These are usually mammals that rest on the shore and hunt for fish in the sea. One of them is the seal, which often climbs onto a nearby platform instead of swimming to the seashore. On the platforms, seals can rest and sunbathe, protected from predators such as wolves. Moreover, a large number of fish accumulate around the platforms, another reason that seals and other mammals are attracted to oil rigs. Species inhabiting areas above the water such as birds and bats also use oil rigs. Many migrating birds for example use the platforms as pitstops. Some stay only for a short time, while others need a longer recovery time (such as wounded or exhausted birds).1 With the ever-growing agricultural use of land and the broader use of pesticides, there are fewer areas for birds to use as pit-stops and find nutrition. Many offshore platforms lie on migration routes, making them convenient pit stops for migrating birds.

1 Russell, Robert W. 2005. Interactions Between Migrating Birds. Louisiana : Louisiana State University, 2005. 1435-01-99-CA-30951-16808.