BP takes step closer to controlling oil spill

CRITICAL tests were under way last night that could put BP close to finally bringing its Gulf of Mexico oil spill under control.

As oil still poured into the sea - up to 211 million gallons have now been spilled since the Deepwater Horizon rig exploded in April - engineers were working to gradually choke off the flow by closing three vents on a newly-installed, 80-tonne containment cap that was fitted on Monday evening.

Once the vents are closed, pressure readings from inside the well will indicate whether the oil can be successfully shut in by the cap, pending a permanent "kill" operation that could be under way by the end of this month using a relief well that has been drilled close by.

But if the readings show that the flow is too powerful to hold back - or if the pressure falls, suggesting a secondary leak - BP will reopen the well and allow the oil to gush again while it brings a new containment system online to divert it onto collection ships.

Kent Wells, a senior vice-president at BP, said: "If we don't get sufficient pressure build-up, it will put in question the integrity of the system. So everyone hope and pray we see high pressures."

Although the installation of the cap had gone "incredibly well", it held no guarantee of success.

He said: "It's not simple stuff and what we don't want to do is speculate around it … we just need to see what the data tells us and make the right decisions going forward."

A statement from the company added: "The sealing cap system never before has been deployed at these depths or under these conditions, and its efficiency and ability to contain the oil and gas cannot be assured."

Even if the oil can be temporarily shut in, the only means of cutting it off permanently is through a relief well that is due to connect with the leaking well two and a half miles below the sea bed by the end of this month.

Once the two intersect, heavy fluids will be poured in via the relief well to "kill" the oil reservoir and seal it. BP has said that the kill could take up to 14 days but aims to have the well stifled for good by 13 August.

Crude oil has been pouring out of the well, named the Macondo Prospect, at between 35,000 and 60,000 barrels per day, according to official government estimates, though doubts remain over the accuracy of that figure.

If the tests show that the oil cannot be safely shut in, the new containment system can handle up to 80,000 barrels a day - but will not reach that capacity until the end of this month.

Though all BP's previous attempts at fixing the leak and stemming the flow have failed, the new containment cap brings with it a higher degree of confidence. It was tailor-built over the last few weeks and described by Admiral Thad Allen, the US federal incident commander, as a "very complex, nuanced and broad-based response" to the crisis, which is the worst environmental disaster in US history and the largest accidental oil spill in the world.

Tens of thousands of people living in Louisiana, Mississippi, Alabama and the Florida Panhandle have suffered economic losses from the disaster, which began with an explosion on the Deepwater Horizon drilling rig on 20 April which killed 11 people. More than one third of the Gulf of Mexico's federal fishing grounds are closed.

Admiral Allen said yesterday that clean-up efforts would last "well into the fall", although scientists fear contamination from the oil and from the 1.7 million gallons of chemical dispersants used to break it up could linger for years, even decades.

US Energy Secretary Steven Chu joined scientists and technical experts overseeing the cap-testing operation from BP's headquarters in Houston, Texas, yesterday.

Mr Wells said yesterday: "We'll all be very happy when we have the well killed and dead. People feel good over what's been done and accomplished over the last couple of days, but we know it's not over yet."z