BP has launched a critical but risky operation aimed at shutting in its blown-out well that has been gushing crude oil into the Gulf of Mexico for nearly three months, creating the worst environmental disaster in U.S. history.
Amid intense anticipation, BP executives were forced to delay the operation for a day to reassure cautious officials from the Obama administration that the sealing of the well would not backfire by opening new fissures in the seabed through which the crude could escape.
In the procedure known as a well integrity test, the company began to close valves on a massive sealing cap installed over the blowout earlier this week. Undersea robots were working about a kilometre below the surface, shutting a sequence of three valves in a capping device installed on Monday. If things go smoothly, they will keep the valves closed as they check pressure readings over a 48-hour period.
Late Wednesday, BP said a leak had been detected near the top of the new cap, but it was isolated and being repaired. BP says on its website the leak was in a line that can funnel oil up to a ship if necessary.
If the well structure is intact, BP expects to keep the well sealed until it can complete a relief well and permanently kill the blowout, some time in early August.
However, BP senior vice-president Kent Wells warned that the operation will have to be abandoned - and the valves reopened - if low pressure readings indicate that the well's cement wall has been ruptured.
"We are proceeding with an overabundance of caution," Mr. Wells said. "The thing we want to pay attention to is making sure that, if we do not have what we call [well]integrity, we do not have a breach to the seafloor."
If pressure tests show the well has been badly damaged, the company will immediately open the flow and resume its effort to capture the oil through various containment options until the completion of the relief well.
After installing the 75-tonne sealing cap on Monday, BP had planned to start the well integrity test on Tuesday. But U.S. Admiral Thad Allen said government officials, led by Energy Secretary Steven Chu, insisted on a 24-hour delay to review the company's plans and get additional assurances.
"There is a tremendous sense of urgency," he said. "But what we didn't want to do was compound the problem by making an irreversible mistake."
Along the Gulf Coast, residents were nervously anticipating BP's latest attempt to stem the flow of crude that has shut down their seafood industry, fouled their wetlands and decimated their tourist industry.
BP has made several unsuccessful attempts to kill the well in the past, including a failed attempt to activate the blowout prevent, a massive valve that is meant to be the last line of defence, and the installation of a smaller cap known as the top hat, and the "junk shot" in which it pumped in mud and debris, including golf balls, in hopes of clogging the hole.
On the Alabama coast, Joyce Nelson said every bit of news from the spill site increases her stress and sparks a new round of telephone calls among friends and relatives in Bayou La Batre, where the seafood industry is virtually shut down because of the spill. The slowdown at the rig site just made things worse.
"Everybody's calling everybody. It's hectic," Ms. Nelson said. "Everybody is worried about them blowing the whole thing out. If that happens, there's nothing they can do but let it drain out."
Adm. Allen said the seismic tests taken this week indicated the sub-sea surface is stable, with no evidence of fractures that would allow the crude to escape outside the well bore. Those seismic readings, plus more detailed engineering information from BP, persuaded the government that the well test could be carried out safely.
Mr. Chu and Adm. Allen will monitor the BP operation, with briefings every six hours, and can call a halt to it if they are advised by their scientists that the risks have become too great.
BP had been capturing an average of 25,000 barrels a day by funnelling the crude to waiting ships and by flaring it, but officials have estimated the Macondo well may be spewing as much as 50,000 barrels a day into the Gulf.
Adm. Allen said the company has increased its containment capacity so that if it is forced to reopen the valves on the sealing cap, it will be able to capture virtually all of the crude. However, it would have to disconnect those systems if a hurricane or major storm rolled through.
Meanwhile, BP has paused in the drilling of the relief well to prevent the well integrity test from interfering with its effort to hone in on the damaged well bore. Adm. Allen said that, regardless of its outcome, the integrity test will provide important information that will help BP engineers determine exactly how to kill the blowout once they intercept it with the relief well.
With a report from Associated Press