BP Plc on Thursday took a significant step toward permanently plugging the ruptured Gulf of Mexico well that caused the world's largest offshore oil spill, the top U.S. official overseeing the spill response said.
Retired Coast Guard Admiral Thad Allen announced late Thursday that BP's relief well bored into the blown-out Macondo well, providing the opening to pump in mud and cement to kill it for good.
"The aggregate data available supports the conclusion that the two wells are joined," Allen said in a statement.
The next step will be to pump cement into the Macondo well near its bottom about 13,000 feet (4,000 metres) beneath the seabed, Allen said.
He also said tests indicated the reservoir already was sealed off from all parts of the Macondo well after BP pumped in cement from the top on Aug. 5. The so-called "bottom kill" is intended to ensure the job is done.
The final kill will come more than two months after BP sealed off all flow with a cap on the wellhead on July 15. Before then, the well spewed more than 4 million barrels of oil into the sea as BP scrambled to seal it with repeated failed efforts.
The disaster began with a blowout on April 20 that sparked an explosion and fire aboard the Deepwater Horizon drilling rig, killing 11 men.
Once the cement cures, BP will conduct pressure tests to ensure the well is dead, Allen said. He said when drilling resumed on the relief well early Wednesday that the entire process could take four days.