BP finished pumping cement into its ruptured oil well in the Gulf of Mexico last night to seal off the source of the world’s worst offshore spill, paving the way to permanently plug the blow-out later this month.
The daylong cementing operation followed earlier injections of heavy drilling mud this week that had subdued the upward pressure of oil and gas inside the deep-sea Macondo well. The crippled wellhead was provisionally capped in mid-July.
“This is not the end, but it will virtually assure us that no oil will be leaking into the environment,” retired Coast Guard Admiral Thad Allen, who oversees the US oil spill response operation, said at a briefing in Washington.
“Monitoring of the well is under way in order to confirm the effectiveness of the procedure,” BP said in a statement announcing completion of the cementing work.
The so-called “static kill” at the top of the well is due to be finished off with a “bottom kill” later in August with more mud and cement injected through a relief bore being drilled into the ruptured well shaft. This relief well is regarded as the final step in plugging the reservoir 13,000 feet (4,000 metres) beneath the seabed.
“I will declare this well dead once we’ve intercepted the annulus [the space between the well pipe and surrounding rock] and we’ve assessed how much mud or cement we need to do from the bottom to finally kill this well,” Allen said.
BP shares hit two-month highs in early trading yesterday on the news that the firm would begin to seal the well with cement. But they later fell back, closing up 0.81 per cent up at 423p.
BP, which has lost over a third of its market value since the 20 April blast that killed 11 workers and sank the Deepwater Horizon rig, , has said it would sell about $30bn (£19bn) in assets to cover costs related to the disaster.
Oil hasn’t flowed into the Gulf since mid-July, when BP installed a temporary cap on top of the damaged well. And the US said this week that 75 per cent of the estimated 4.9m barrels of oil spewed by the well has either evaporated, dispersed or otherwise been contained.