BP began drilling Monday the final stretch of a relief well that will allow engineers to permanently seal its disastrous Macondo well in the Gulf of Mexico.
Drilling stopped more than a month ago due to the threat posed by a tropical storm, and a lengthy debate over how best to proceed then delayed the final kill operation by several weeks.
But US spill chief Thad Allen gave the go-ahead for drilling to resume after a sleeve was installed on the wellhead at the weekend to prevent any pressure problems with the “bottom kill” procedure.
Allen says it will take BP four days to drill out the remaining 50 feet (15 meters) vertically and four feet (1.2 meters) horizontally to intercept the Macondo well 3.4 miles (5.5 kilometers) under the Gulf of Mexico.
“Following the intercept, heavy drilling mud and cement will be pumped into the annular space to complete the isolation of the MC252 well,” a BP statement said.
A “static kill” with mud and cement pumped in from above plugged the well six weeks ago, but Allen has insisted that the annulus — the area between the well and the outer well bore — must also be sealed off from the reservoir.
“I will continue to provide updates on the progress of the relief well, the final step that will ensure the well is fully and finally killed, as necessary,” the former Coast Guard chief said in a statement Monday.
An estimated 4.9 million barrels of oil gushed out of the well off the coast of Louisiana after it was ruptured by an April 20 explosion aboard BP’s Deepwater Horizon drilling rig that killed 11 workers.
It took 87 days to stem the flow of oil into the sea and hundreds of miles of coastline from Texas to Florida were sullied, killing wildlife and devastating key local industries such as tourism and fishing.
Most of the massive slick has been dispersed, dissolved, burned off or skimmed off the surface, but some scientists warn that the full impact of what was the world’s largest ever maritime spill may not be known for decades.
BP has already spent eight billion dollars trying to contain the disaster and has forecast that it will eventually cost the group more than 32.2 billion dollars.