BP’s Macondo oil well in the Gulf of Mexico was finally shut down on 18 September, as a final squirt of cement sealed the source of America’s largest ever oil spill.

Drilling into the well shaft more than 4,000 metres beneath the sea floor, engineers injected cement into it from below, marking the end of the well which began leaking after the Deepwater Horizon drilling rig exploded and sank in April. Since then it is estimated that around 5 million barrels of oil leaked into the Gulf before the well was capped in July.

“We can finally announce that the Macondo 252 well is effectively dead,” said the National Incident Commander, Admiral Thad Allen (statement). “Additional regulatory steps will be undertaken but we can now state, definitively, that the Macondo well poses no continuing threat to the Gulf of Mexico.”

Deepwater Horizon took nearly five months to completely seal, from the date of the accident. This doesn’t look quite so bad when you compare it to the famous Ixtoc well in the Gulf, which blew in June 1979 and wasn’t capped till March 1980 (see: The lost legacy of the last great oil spill).

Of course, there is still the small matter of those 5 million barrels of oil.

“Our work is not finished, however. BP remains committed to remedying the harm that the spill caused to the Gulf of Mexico, the Gulf Coast environment, and to the livelihoods of the people across the region,” said BP America Chairman and President Lamar McKay (statement).

Image: the Deepwater Horizon wellhead on 29 July / US Coast Guard photograph by Petty Officer 1st Class Adam Eggers.