Nature Platforms
HOW? ANALYSIS AND RESEARCH 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 lattice framework construction of the Bullwinkle platform was prefabricated on land and towed into the Gulf of Mexico in 1988.
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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.
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 23
