NEW ORLEANS — Robotic submarines working a mile underwater removed a leaking cap from the gushing gulf oil well Saturday, starting a painful trade-off: Millions more gallons of crude will flow freely into the sea for at least two days until a new seal can be mounted to capture all of it.
There's no guarantee for such a delicate operation, officials said. A permanent plugging of the well from the bottom remains slated for mid August.
"It's not just going to be, you put the cap on, it's done. It's not like putting a cap on a tube of toothpaste," Coast Guard spokesman Capt. James McPherson said.
Robotic submarines removed the cap placed last month to collect oil and send it to surface ships for collection or burning. BP aims to have the new, tighter cap in place as early as Monday and said that, as of Saturday night, the work was going according to plan.
"Over the next four to seven days, depending on how things go, we should get that sealing cap on. That's our plan," said Kent Wells, a BP senior vice president, of the round-the-clock operation.
It would be only a temporary solution to the catastrophe that began April 20 when an explosion killed 11 people and opened a tap that the federal government estimates has poured between 87 million and 172 million gallons of oil into the gulf. Hope for permanently plugging the leak lies with two relief wells, the first of which could be finished by mid August.
With the cap removed Saturday afternoon oil flowed freely into the water, collected only by the Q4000 surface vessel, with a capacity of about 378,000 gallons. That vessel should be joined today by the Helix Producer, which has more than double the Q4000's capacity.
But the lag could be long enough for as much as 5 million gallons to gush into waters. Officials said a fleet of large skimmers was scraping oil from the surface above the well site.
BP began trying Saturday afternoon to remove the bolted top flange that only partly completed the seal with the old cap. Video images showed robotic arms working to unscrew its bolts. Wells said that could last into Monday, depending on whether the flange can be pulled off from above, as BP hopes. If not, a specially designed tool will be used to pry the union apart.
Once the top flange is removed, BP has to bind together two sections of drill pipe that are in the gushing well head. Then a 12-foot-long piece of equipment called a flange transition spool will be lowered and bolted over it.
After that, the new cap — called a capping stack or "Top Hat 10" — can be lowered. The equipment, weighing some 150,000 pounds, is designed to fully seal the leak and provide connections for new vessels on the surface to collect oil. The cap has valves to stop the flow if it can withstand the enormous pressure.