Robot sub used to plug deep Gulf oil leak

Crews were using a robot submarine to try to stop an oil leak nearly 2km below the surface of the Gulf of Mexico, but officials said it would take at least another day before they knew whether the job was completed.

It could take hours or it could take months to stop the 15,900-litre-a-day oil leak at the site of a wrecked drilling platform. Whether the environmental threat grows many times bigger depends on whether the oil company can turn off the well completely.

Crews are using robot submarines to activate valves at the well head in hopes of cutting off the leak, which threatens the Gulf Coast's fragile ecosystem of shrimp, fish, birds and coral. If the effort fails, they'll have to start drilling again.

The submarine work will take 24 to 36 hours, Doug Suttles, chief operating officer for BP Exploration and Production, said yesterday.

"I should emphasise this is a highly complex operation being performed at 1520m below the surface and it may not be successful."

Oil continued to leak nearly 1.5km underwater at the site where the Deepwater Horizon rig exploded last week. Eleven workers are missing and presumed dead.

For the second consecutive day, high waves prevented boats and equipment from going out to clean the spill. Airplanes sprayed chemicals to break up the oil. The spill initially appeared to be easily manageable after the oil rig sank on Friday about 80km off the Louisiana coast, but it has turned into a more serious environmental problem. Officials on Sunday discovered the leak, which is spewing as much as 1000 barrels of oil each day. The oil spill has been growing - officials said the oily sheen on the surface of the gulf covered about 1550sq km yesterday. The environmental damage would be especially serious if it reaches land.

The spill was still about 112km from the mainland, but only about 48km from an important chain of barrier islands known as the Chandeleurs.

The islands, part of a national wildlife refuge, are an important nesting ground for pelicans and other sea birds. They have been under serious threat since Hurricane Katrina washed out much of the sand there.

"[The spill] has the potential to be pretty serious, but at 1000 barrels a day, if it comes to the surface they'll probably be able to contain it and vacuum it up," said James Cowan, an oceanography and coastal sciences professor at Louisiana State University.

Suttles said the company plans to collect leaking oil on the ocean bottom by lowering a large dome to capture the oil and using pipes and hoses to pump it into a vessel on the surface.

"That system has been deployed in shallower water," he said, "but it has never been deployed at 1520m of water, so we have to be careful."

The robot submarines are attempting to close off the flow of oil by activating a shutoff device at the well head known as a blowout preventer. In case that doesn't work, BP PLC, which leased the Deepwater, moved another deepwater rig, the DD3, towards the explosion site. If necessary, the new rig would drill relief wells into the damaged well underneath the ocean floor. That could take several months.

Benton Baugh, who holds numerous patents for blowout preventer parts, said the subs should be able to do the job.

"If they can't get it closed off, something really unusual happened."

Kenneth E. Arnold, an offshore production facility expert, said drilling a relief well is not an easy task.

"You have to intersect the well," he said. "Sometimes you have to drill through the steel, and that's what happened in Australia. It took them three times before they were successful."

He was referring to a blowout on the West Atlas rig in the Timor Sea last August. It wasn't until November that mud could be pumped through a relief well to shut off the deepwater spigot. The oil spill has resulted in major environmental damage along the coast of East Timor and Indonesia.

Coast Guard officials said weather conditions for the next three days would help keep the Gulf spill away from the coast.

Mark Schexnayder, a regional coastal adviser at the Louisiana Sea Grant, said the oil spill had the potential to do long-term damage. The location of the spill is crisscrossed by marine species, including sperm whales, whale sharks, sea turtles, grouper and porpoises.

"We're a month away from opening up the inshore shrimp season, crab season is just getting under way," he said. "It could close oyster beds."

- AP