Blown-out BP well sealed once and for all

The leaking Deepwater Horizon oil well has been finally killed off.

A permanent cement plug sealed BP's well nearly 2.5 miles down in the Gulf of Mexico, five agonising months after an explosion sank a drilling rig and led to the worst offshore oil spill in US history.

Retired Coast Guard Admiral Thad Allen, the federal government disaster supremo, described BP's well as "effectively dead".

He said a pressure test to ensure the cement plug would hold was completed at 5:54 am local time.

"We can now state definitively that the Macondo Well poses no continuing threat to the Gulf of Mexico," Allen said.

The gusher was contained in mid-July after a temporary cap was successfully fitted atop the well. Mud and cement were later pushed down through the top of the well, allowing the cap to be removed.

But the well could not be declared dead until a relief well was drilled so that the ruptured well could be sealed from the bottom.

The explosion on board the rig on 20 April, 2010, killed 11 workers, and set loose one billion litres of oil, causing an environmental and economic nightmare for people who live, work and play along the hundreds of miles of Gulf shoreline from Florida to Texas.

It also started civil and criminal investigations and brought increased governmental scrutiny of the oil and gas industry, including a costly moratorium on deepwater offshore drilling that is still in place.

Gulf residents will be feeling the pain for years to come. There is still plenty of oil in the water, and some continues to wash up on shore. Many people are still struggling to make ends meet with some fishing grounds still closed to fishing.