Size of spill in Gulf of Mexico is larger than thought

posted on:
April 29, 2010

author:
Campbell Robertson and Leslie Kaufman

category:
Environmental

NEW ORLEANS – Government officials said late Wednesday night that oil might be leaking from a well in the Gulf of Mexico at a rate five times that suggested by initial estimates.

In a hastily called news conference, Rear Adm. Mary E. Landry of the Coast Guard said a scientist from the National Oceanic and Atmospheric Administration had concluded that oil is leaking at the rate of 5,000 barrels a day, not 1,000 as had been estimated. While emphasizing that the estimates are rough given that the leak is at 5,000 feet below the surface, Admiral Landry said the new estimate came from observations made in flights over the slick, studying the trajectory of the spill and other variables.

An explosion and fire on a drilling rig on April 20 left 11 workers missing and presumed dead. The rig sank two days later about 50 miles off the Louisiana coast.

Doug Suttles, chief operating officer for exploration and production for BP, said a new leak had been discovered as well. Officials had previously found two leaks in the riser, the 5,000-foot-long pipe that connected the rig to the wellhead and is now detached and snaking along the sea floor. One leak was at the end of the riser and the other at a kink closer to its source, the wellhead.

But Mr. Suttles said a third leak had been discovered Wednesday afternoon even closer to the source. “I’m very, very confident this leak is new,” he said. He also said the discovery of the new leak had not led them to believe that the total flow from the well was different than it was before the leak was found.

The new, far larger estimate of the leakage rate, he said, was within a range of estimates given the inexact science of determining the rate of a leak so far below the ocean’s surface.

“The leaks on the sea floor are being visually gauged from the video feed” from the remote vehicles that have been surveying the riser, said Doug Helton, a fisheries biologist who coordinates oil spill responses for the National Oceanic and Atmospheric Administration, in an e-mail message Wednesday night. “That takes a practiced eye. Like being able to look at a garden hose and judge how many gallons a minute are being discharged. The surface approach is to measure the area of the slick, the percent cover, and then estimate the thickness based on some rough color codes.”

Admiral Landry said President Obama had been notified. She also opened up the possibility that if the government determines that BP, which is responsible for the cleanup, cannot handle the spill with the resources available in the private sector, that Defense Department could become involved to contribute technology.

Wind patterns may push the spill into the coast of Louisiana as soon as Friday night, officials said, prompting consideration of more urgent measures to protect coastal wildlife. Among them were using cannons to scare off birds and employing local shrimpers’ boats as makeshift oil skimmers in the shallows.

Part of the oil slick was only 16 miles offshore and closing in on the Mississippi River Delta, the marshlands at the southeastern tip of Louisiana where the river empties into the ocean. Already 100,000 feet of protective booms have been laid down to protect the shoreline, with 500,000 feet more standing by, said Charlie Henry, an oil spill expert for the National Oceanic and Atmospheric Administration, at an earlier news conference on Wednesday.

On Wednesday evening, cleanup crews began conducting what is called an in-situ burn, a process that consists of corralling concentrated parts of the spill in a 500-foot-long fireproof boom, moving it to another location and burning it. It has been tested effectively on other spills, but weather and ecological concerns can complicate the procedure.

Such burning also works only when oil is corralled to a certain thickness. Burns may not be effective for most of this spill, of which 97 percent is estimated to be an oil-water mixture.

A burn scheduled for 11 a.m. Wednesday was delayed. At 4:45 p.m., the first small portion of the spill was ignited. Officials determined it to be successful.

Walter Chapman, director of the Energy and Environmental Systems Institute at Rice University, said a 50 percent burn-off for oil within the booms would be considered a success. Admiral Landry called the burn “one tool in a tool kit” to tackle the spill. Other tactics include: using remote-controlled vehicles to shut off the well at its source on the sea floor, an operation that has so far been unsuccessful; dropping domes over the leaks at the sea floor and routing the oil to the surface to be collected, an operation untested at such depths that would take at least two to four more weeks; and drilling relief wells to stop up the gushing cavity with concrete, mud or other heavy liquid, a solution that is months away.

The array of strategies underscores the unusual nature of the leak. Pipelines have ruptured and tankers have leaked, but a well 5,000 feet below the water’s surface poses new challenges, officials said.

Reached in southern Louisiana on Wednesday, where he was visiting the response team’s command center, Tony Hayward, the chief executive of BP, said he did not yet know what went wrong with the oil rig. BP, which was leasing the rig from Transocean, is responsible for the cleanup under federal law.

Until Wednesday night, the well had been estimated to be leaking 1,000 barrels, or 42,000 gallons, each day.

The response team has tried in vain to engage a device called a blowout preventer, a stack of hydraulically activated valves at the top of the well that is designed to seal off the well in the event of a sudden pressure release – a possible cause for the explosion on the rig.

Mr. Hayward said the blowout preventer was tested 10 days ago and worked. He said a valve must be partly closed, otherwise the spillage would be worse.

There are a number of things that can go wrong with a blowout preventer, said Greg McCormack, director of the Petroleum Extension Service at the University of Texas, which provides training for the industry.

The pressure of the oil coming from below might be so great that the valves cannot make an adequate seal. Or in the case of a shear ram, which is designed to cut through the drill pipe itself and seal it off, it might have encountered a tool joint, the thicker, threaded area where two lengths of drilling pipe are joined.

Still, Mr. McCormack said, “something is working there because you wouldn’t have such a relatively small flow of oil.” If the blowout preventer were completely inoperable, he said, the flow would be “orders of magnitude” greater.

Mr. Hayward, of BP, said the crude spilling from the well was very light, the color and texture of “iced tea” and implied that it would cause less environmental damage than heavier crude, like the type that spilled from the Exxon Valdez into Prince William Sound in 1989. He said in most places it was no more than a micron thick and in the thickest areas was one-tenth of a millimeter, or the width of a hair.

Mr. Hayward declined to answer questions about any potential political fallout and said BP “will be judged primarily on the response.”

As the investigation into the cause continued, officials, scientists and those who make their living on the Gulf Coast were focused on the impending prospect of the oil’s landfall.

 

Campbell Robertson reported from New Orleans, and Leslie Kaufman from New York. Henry Fountain and Liz Robbins contributed reporting from New York.

 

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