(CNN) -- Experts still hope to close a stuck valve that's let oil flow into the Gulf of Mexico for more than a week. But if those efforts fail, the next-best plans will take weeks more to stop the flow, officials say.
The undersea oil well, following a drilling rig's April 20 explosion 50 miles off Louisiana's coast, is spewing up to 210,000 gallons of light sweet crude a day into the Gulf, officials say.
Eleven workers from the rig are missing and presumed dead.
Part of the Gulf Coast was bracing for oily water to reach shore early Friday.
BP, the well's majority owner, has been trying to stop the flow by using remote-controlled submarines to activate a valve atop the well. But the valve, known as a blowout preventer, is not working.
A stopgap plan -- putting a chamber over the well area and sending the oil to a ship -- is unproven at that depth and could take four weeks before it's ready. And the ultimate plan -- drilling a different well to access the first and close it with concrete -- could take three months. Meanwhile, efforts to contain the spill and stop the leak are costing the well's owners about $6 million per day, BP says.
"Our focus first and foremost is how to bring this event to an end by stopping the flow of oil as quickly as we can," Doug Suttles, chief operating officer of BP's global exploration and production business, said at a news conference Thursday.
As the well's owner, BP is obligated to see to the cleanup and leak stoppage. Here's what BP says it is trying to do to stop the leak, and why each approach is taking time.
Activating the blowout preventer
When Transocean's rig sank, a steel riser that connected the rig to the well collapsed to the ocean floor, and eventually remote-operated submarines would find three leaks coming from the riser or a related drill pipe.
The blowout preventer -- a 48-foot-tall, 450-ton apparatus that sits atop the well 5,000 feet underwater -- will stop the flow if crews can get it to work. The device -- owned by the rig's owner, Transocean -- should have activated on the day of the blast, Tony Hayward, CEO of BP Group, told CNN's Brian Todd in an interview Wednesday.
Suttles said Thursday that workers aboard Transocean's rig, before it sank, tried to manually activate the blowout preventer.
"We actually don't know why the blowout preventer has failed to stop the flow," Suttles said. "Ultimately we'll recover [it] ... and we'll find out, but that could be quite some time."
For days, BP contractors have used remote-controlled submarines with robotic arms to try to reach access portals and activate the valve.
"We've tried many different ways. Some things have showed promise, some haven't," BP spokesman Daren Beaudo said in a phone interview. "We're going to keep doing it until we're successful or we've exhausted our options [with the submarines].
"We don't know why the remote-operated shutdown systems haven't worked," Beaudo said.
Stopgap: Capturing the oil from the well
Patching the leaks themselves isn't possible, Suttles said. But, anticipating the submarines might never get the blowout preventer to work, BP has been working on a plan to collect the oil directly from the leaks so that it doesn't go into the ocean.
The plan calls for designing and manufacturing three containment chambers that will cover the leak. Pipes attached to those chambers would send the oil to a ship above.
The method isn't new -- it has been done in more shallow waters. But not at this depth, BP believes.
"We're not sure it's going to work, but it's certainly something worth attempting" Beaudo said. "What we've done is challenged our engineers to design something that could withstand pressures at 5,000 feet and go through a mile of water to a vessel."
One chamber has been made, and two others are coming. But completing this system for this depth takes time -- it should be ready within four weeks, BP said Thursday in a news release.
Even if the chamber system works, BP still would need a way to stop the oil. And that's where the relief well would come in.
Drilling the relief well
To permanently seal the well -- regardless of whether the blowout preventer works -- BP is preparing to drill a second well at an angle to intercept the first one. Once contact is made, drilling fluid and concrete will be put into the first well, Beaudo said.
BP has received a permit for this second well, and drilling from a contractor's rig could begin Friday. However, it won't be finished anytime soon.
"It takes roughly a couple months to 90 days to drill like this," Beaudo said. "We would go down 5,000 feet of water, then drill directionally through about 13,000 feet of subsurface." Weather conditions also could prolong the process, he said.
Which means that if the blowout preventer and chamber methods don't work, it could be many weeks before the oil stops leaking into the Gulf.
BP said it wasn't necessarily married to just these three options. It said it has reached out to other experts -- including those from rival oil companies -- to see whether they have other ideas to stop the leaks. All ideas will be considered, Suttles said.
"I don't know if we'll be able to stop it today or whether it will ultimately take a relief well. What I don't want to occur is this oil continuing to reach the surface of the sea," Suttles said.