The recent incident on Shell UK’s offshore oil rig, the Brent Alpha, is just one indicator of the safety issues inherent in decommissioning. With no warning, a lifeboat on the rig lowered to the water during routine maintenance. The failure of the clutch securing the lifeboat to the rig did not cause any injuries but highlights the possible danger of aging rigs. The next several years will see a decommissioning boom with oceanic oil rigs.
Decommissioning activities include the closure of all production facilities and wells, the removal of structures above the ocean floor and rig material reclamation. Abandoned wells, jackets, decks, topsides and subsea pipelines all need decommissioning.
Factors impacting removal decisions during decommissioning are environmental, regulatory, safety and monetary concerns. Some government regulations stipulate full removal only, where other regulations are more flexible. The environmental issues existing at some rig sites put additional support behind full site rehabilitation. Oil companies, looking at mounting decommission costs, favor the most economical closings possible.
Even though the safest avenue for workers is to leave the rig as is or partially remove the structure, many governments object to these approaches and want their waters left in the same condition as they were before the oil company started building the rig. Therefore, there is a great amount of support for complete rig removal and site restoration. The option of collapsing the rig onsite has both supporters and detractors.
Faulty closing procedures can lead to safety hazards during dangerous activities such as work in confined spaces. If the atmosphere does not receive constant monitoring, hazardous conditions are missed which can lead to asphyxiation of workers, fire or explosive activity. Restoration activities can include extensive removal of environmental contaminants which raises exposure risks. Improper handling procedures can expose the workers involved as well as the environment.
In addition to well plugging, removal of all platform components must be down to at least 15 feet below ground. Methods of removal introduce additional risk elements to decommissioning. One method involves explosive activity to cut conductors, and another uses a crane to pull down segments of the conductor casings.
The unpredictability of the dismantling process is, at best, more dangerous than the oil rig construction process. It is apparent that the growing number of oil rigs undergoing decommissioning will highlight the need to adhere to proper procedures to facilitate worker safety.