BP plans to seal Gulf of Mexico oil well on Tuesday
BP says it plans to inject mud and possibly cement into its Gulf of Mexico oil well on Tuesday, in one of the final steps to permanently seal it.
The "static kill", as the procedure is called, will begin if preliminary tests are positive, a BP executive said.
More mud and cement would then be pumped in from a relief well within five to seven days, said the US Coast Guard officer overseeing the operation.
Only that "bottom kill" would fully seal the well, said Admiral Thad Allen.
"We want to confirm we can inject the oil in the wellbore back into the reservoir," said Kent Wells, BP's senior vice-president of exploration and production.
If the tests are positive "then we move to the static kill", he said.
The well has been temporarily sealed for two weeks after spilling up to 60,000 barrels of oil a day into the sea since 20 April, when an explosion on a drilling rig off Louisiana killed 11 workers and triggered the leak.
Last week, BP reported a record $17bn (£11bn) loss, having set aside $32bn to cover the costs of the spill - the worst in US history.
It has caused environmental damage and huge economic losses in four states.
'Bottom kill' crucial
The static kill, also known as "bullheading" takes place in three stages.
- First, a test determines if oil can be pushed back down the well into the reservoir
- If that goes well, the static kill is begun by pumping in mud at low pressure. That may take all of Tuesday and possibly run into Wednesday
- Then, engineers will have to decide whether to pump in cement at the top of the well or wait and pump in cement from the relief well into the bottom of the damaged well.
The relief well will reach the damaged well some time between 11 and 15 August.
The permanent "bottom kill" will take anywhere between a number of days and a few weeks. The final casing has been cemented in place, which is the prelude to the last bit of drilling.
An earlier effort to pump mud into the well using much of the same equipment at the end of May failed because the pressure of the spewing oil and gas was too great.
Adm Allen said he would travel to BP's headquarters in Houston to oversee the static kill, and that engineers would know within hours if was successful.
"The static kill is not the end-all, be-all," Mr Allen said.
If any leaks are detected during the procedure over the coming days, technicians will seek to identify them through seismic work and other diagnostic testing.
During Sunday's news conference, Mr Allen also defended the use of chemical dispersants by BP to break up oil slicks created by the spill, despite concerns expressed about their environmental impact.
"Sometimes there is no other way to attack the oil," he said, denying he had clashed with the head of the Environmental Protection Agency over the matter.
"There is no disagreement between Lisa Jackson and I regarding what we want to do with dispersants," he added.