Interesting question. You can’t just walk away from it, especially nowadays, between regulations, environmental questions, liability concerns, p.r. “optics,” volatile oil prices and Lord knows what else. But decommissioning it is no simple matter either. It involves a good deal more that shutting off the lights and locking the doors.
And the list linked above refers to work in the relatively shallow and peaceful (not counting hurricanes) waters of the Gulf of Mexico. Now consider the huge oilfields in the North Sea. These fields, which have been pumping substantial quantities of oil since the 1960s, are beginning to reach the end of their useful life, and while North Sea supplies are nowhere near exhausted yet, the handwriting is on the wall, and plans are in the works for what happens next.
The Brent field, owned by Shell, about 115 miles (186 km) off the coast of the Shetland Islands northeast of Scotland is winding down. Only one of its four rigs is still pumping oil, and now Shell is undertaking the massive project of removing the structures and plugging the wells.
Right now, Shell’s focus is on dismantling the Delta platform, one of the largest projects Shell has undertaken. It involves, for a start, removing the platform itself in a single 23,000-tonne piece by a purpose-built ship and delivering it to a facility in Hartlepool, Teesside, in northeastern England, where it will be dismantled. For all the juicy engineering details, go here.
And for extra-credit reading on great big decommissioning projects, go to this account of building a containment dome over Chernobyl. It won’t, perhaps, be as elegant as Brunelleschi’s dome over the Duomo in Florence, Italy, but then Brunelleschi wasn’t distracted by the radiation levels in his work space.