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Overview
An explosion on April 20 aboard the Deepwater Horizon, a drilling rig working on a well for the oil company BP one mile below the surface of the Gulf of Mexico, led to the largest accidental oil spill in history. After a series of failed efforts to plug the leak, BP said on July 15 that it had capped the well, at least temporarily, marking the first time in 86 days that oil was not gushing into the gulf.
The slick appeared to be dissolving far more rapidly than anyone expected. The immense patches of surface oil that covered thousands of square miles of the gulf after the April 20 explosion are largely gone, though sightings of tar balls and emulsified oil continued here and there. Radar images suggest that the few remaining patches are quickly breaking down in the warm surface waters of the gulf. Officials in charge of the response say they are beginning to shift their efforts to a new phase, focusing more on long-term recovery now that some of the urgent demands of the spill are diminishing.
The BP spill is by far the world's largest accidental release of oil into marine waters, according to the most precise estimates yet of the well's flow rate, announced by federal scientists on Aug. 2. Nearly five million barrels of oil have gushed from BP's well — and about 800,000 have been captured by containment efforts —since the Deepwater Horizon rig exploded. The amount outstrips the estimated 3.3 million barrels spilled into the Bay of Campeche by the Mexican rig Ixtoc I in 1979, previously believed to be the world's largest accidental release.
The oil from the gulf spill first made landfall in Louisiana. But in June, tar balls and oil mousse began to reach the shores of Mississippi, Alabama and Florida.
Initially, the Coast Guard and the oil company worked to contain the slick within booms and succeeded in burning small amounts of oil. The slick spread mainly to the south and east, and by mid-May it was beginning to enter the loop current that steers Gulf waters toward Florida.
Shortly thereafter it began to hit shore, smearing tourist beaches, washing onto the shorelines of sleepy coastal communities and oozing into marshy bays that fishermen have worked for generations. It announced its arrival on the Louisiana coast with a fittingly ugly symbol: brown pelicans, the state bird, dyed with crude.
On June 1, the Justice Department announced that it would begin a criminal investigation of the spill, to determine if any of the parties involved — BP, which was leasing the rig, which made it liable for the spill's damage; Transocean, which owned the rig; and Halliburton, which was involved in the effort to seal the well that preceded the blast — had violated environmental laws.
Congressional investigators were told of sharp conflicts in the hours before the blast, which killed 11 workers, over how to handle the capping of the well, and uncovered evidence of missed warning signs. An internal memo showed that BP had chosen the cheaper of two methods of capping, despite worries about the risks involved.
As the weeks dragged on and BP failed repeatedly to plug the leak, the spill grew into a major political challenge for President Obama. It upended the debate on his proposal in March to expand offshore drilling — he halted virtually all drilling projects in late May — and seemed to derail a bipartisan attempt at energy and climate legislation in the Senate.
An oil-weary nation waited more than three months for the moment when engineers would begin pumping cement into BP's runaway well, in hopes of plugging its flow for good. The moment arrived quietly on Aug. 5, with cement following the tons of mud already poured into the well the day before during a "static kill" operation. The static kill, in all likelihood, sealed the volatile well permanently.
The Explosion
A confidential survey of workers on the Deepwater Horizon in the weeks before the oil rig exploded, commissioned by Transocean, showed that many of them were concerned about safety practices and feared reprisals if they reported mistakes or other problems.
In the survey workers said that company plans were not carried out properly and that they "often saw unsafe behaviors on the rig."
According to a separate 112-page equipment assessment also commissioned by Transocean, many key components — including the blowout preventer rams and failsafe valves — had not been fully inspected since 2000, even though guidelines require inspection of the preventer every three to five years.
The two Transocean-commissioned reports echoed the findings of a maintenance audit conducted by BP in September 2009. But the Transocean-commissioned reports indicate that maintenance concerns existed just days before the explosion and the rig owner was aware of them.
Information coming from a variety of sources about the events that led up to the blast paint a picture of a complex operation that went awry just as it was drawing to a close.
Drilling logs from the Deepwater Horizon suggest that shortly after midnight on the morning of the explosion, attention had turned to temporarily plugging and capping the well so the rig could disconnect and move to another job. Halliburton, the contractor hired by BP to provide cementing services, had spent the past several weeks cementing each new segment of the well into place. Halliburton was also responsible for plugging it.
BP and Congressional investigators have raised questions about the cementing, suggesting that the seal might have been faulty and failed to keep gas from rising up in the well. According to BP, the cement work took longer than normal, and there were concerns that the quality of the cement might have been compromised by contamination with mud. Halliburton executives have said that the company adhered strictly to the specifications provided by BP for the cementing of the well.
The Government's Response
From the beginning, the response effort was bedeviled by a lack of preparation, organization, urgency and clear lines of authority among federal, state and local officials, as well as BP.
On April 29, Mr. Obama announced that the federal government would get involved more aggressively in fighting the spill, and Homeland Security Secretary Janet Napolitano designated the spill as "of national significance.''
Interior Secretary Ken Salazar, who early in the crisis vowed to "keep the boot on the neck" of BP, threatened to push the company out of the way. But Mr. Salazar soon backed off, conceding to the reality that BP and the oil companies have access to the best technology to attack the well. The government's role, he acknowledged, is largely supervisory and the primary responsibility for the spill, for legal and practical reasons, remains with the company.
The White House said that the government would not allow any new offshore drilling until an investigation was conducted into the spill and whether it could have been prevented. But the Interior Department continued to issue permits and waivers for drilling projects in the gulf that were already underway, leading critics to say the ban was being interpreted too narrowly.
After the White House announced it would open civil and criminal investigations into the oil spill, BP said it will cooperate fully with any inquiry, which may also extend to Transocean, Halliburton or Cameron, the company that manufactured the blowout preventer that failed to function after the explosion.
Mr. Obama has made four trips to the Gulf region since the spill began. On June 15, he gave his first Oval Office speech, in which he used the crisis to press for sweeping change in energy policy. He also appointed former Mississippi Governor Ray Mabus as long-term recovery coordinator and demanded that BP set up a multibillion-dollar escrow account to compensate the victims.
The following day, top executives of BP went to the White House and agreed to create a $20 billion fund to pay claims for the spill. The fund will be independently run by Kenneth Feinberg, the mediator who oversaw the 9/11 victims compensation fund. BP also said it would not pay further dividends to shareholders in 2010.
Tony Hayward, BP's chief executive, and other executives faced harsh questioning from Congress, and oil company executives speaking at a Congressional hearing publicly blamed BP for mishandling the well that caused the disaster.
Representative Edward J. Markey, the chairman of the House Energy and Environment Subcommittee, released an internal BP document on June 20 showing that the company's own analysis of damage to the well bore resulted in a worst-case estimate of 100,000 barrels of oil leaking into the Gulf of Mexico each day. Mr. Markey said the document provided a sharp contrast to BP's initial claim that the leak was just 1,000 barrels a day.
Mr. Hayward was replaced in late July by Robert Dudley, BP's Mississippi-born managing director, after Mr. Hayward's repeated stumbles alienated federal and state officials as well as residents of the Gulf Coast.
Mr. Dudley said upon his appointment that the oil giant remained committed to its business in the United States, as it moved to sell $30 billion in assets before 2012 to pay for costs related to the spill.
Impact on Energy Policy
The deadly explosion and the resulting spill complicated Mr. Obama's plans to expand offshore oil and gas drilling, and doomed a bipartisan energy bill in the Senate in 2010. Mr. Obama announced plans to split the Minerals Management Service, the agency that oversees offshore oil drilling, into two parts, one to inspect oil rigs and enforce safety and the other to oversee leases for drilling and collect royalties.
Mr. Obama ordered a halt to virtually all current and new offshore oil drilling activity pending a comprehensive safety review. He acknowledged that oversight had been seriously deficient, but said that offshore drilling would have to remain a part of the nation's sources of energy for at least the near future.
Mr. Obama began a push for action on energy legislation, hoping to capitalize on growing public anger toward BP and other oil companies. He called for rolling back Bush-era tax breaks for energy companies, and directing the funds toward clean energy research.
In his Oval Office speech on June 15, Mr. Obama made the case that the spill justifies his plans for energy and climate change legislation, a way of turning a political burden into a political weapon. He called on Americans to "seize the moment" to "end America's century-long addiction to fossil fuels."
Republicans quickly accused Mr. Obama of capitalizing on the leaking oil to pass a bill that otherwise seemed stalled.
Blowout Preventers
After the explosion, investigators focused on the failure of a component on the well's blowout preventer that is supposed to close off a well spewing out of control. The device, called a blind shear ram, is the only part of the blowout preventer that can completely seal the well. Minutes after the explosion, at least one rig worker hit an emergency button, which is supposed to trigger the blind shear ram within about 30 seconds, and then disconnect the rig from the well. But the blind shear ram never fully deployed.
An examination by The New York Times revealed the chasm between the oil industry's assertions about the reliability of its blowout preventers and a more complex reality. It reveals that the Minerals Management Service, repeatedly declined to act on advice from its own experts on how it could minimize the risk of a blind shear ram failure.
It also shows that the Obama administration failed to grapple with either the well-known weaknesses of blowout preventers or the sufficiency of the nation's drilling regulations even as it made plans in March to expand offshore oil exploration.
Records and interviews show that blind shear rams can be surprisingly vulnerable. There are many ways for them to fail, some unavoidable, some exacerbated by the stunning water depths at which oil companies have begun to explore.
They also can be rendered powerless by the failure of a single part, a point underscored in a confidential report that scrutinized the reliability of the Deepwater Horizon's blowout preventer.
The Struggle Underwater
BP clashed with the federal government over its use of dispersants, chemicals sprayed on the spill that were meant to break up the oil in the hope that it would settle to the bottom.
For weeks BP tried without success to reactivate the seal-off valves on the dead blowout preventer. Then it lowered a 40-foot steel containment chamber in an effort to funnel escaping oil to a ship on the surface, but that failed when an icy slush of gas and water stopped up the device.
In a maneuver called a "top kill," BP planned to pump heavy drilling fluids twice the density of water through two narrow lines into the blowout preventer to plug the runaway well. However, this tactic, though initially promising, failed when it became clear that the pressure of oil and gas escaping from the well was simply too powerful to overcome. With this disappointment, BP and government officials announced they had abandoned efforts to plug the leaking well.
BP engineers used submersible robots to cut off a portion of the pipe the oil was gushing through to give a new cap a better target to fit over, and pumped antifreeze down into the space to try to prevent ice buildup. They then eased the cap in place, and slowly began closing vents that had been left open to minimize pressure that might lift it off. By June 5, officials reported that they were siphoning off as much as 10,000 barrels a day, even with only one of four vents closed.
In mid-July, after 86 days of oil gushing into the gulf, the leak was finally stopped when BP managed to install a much tighter-fitting cap on the well a mile below the sea floor, then gradually closed a series of valves.
Prospects for Recovery
The effect on sea life of the large amounts of oil that dissolved below the surface is still a mystery. Two preliminary government reports on that issue have found concentrations of toxic compounds in the deep sea to be low, but the reports left many questions, especially regarding an apparent decline in oxygen levels in the water.
And understanding the effects of the spill on the shorelines that were hit, including Louisiana’s coastal marshes, is expected to occupy scientists for years. Fishermen along the coast are deeply skeptical of any declarations of success, expressing concern about the long-term effects of the chemical dispersants used to combat the spill and of the submerged oil, particularly on shrimp and crab larvae that are the foundation of future fishing seasons.
Scientists said the rapid dissipation of the surface oil was probably due to a combination of factors, including the gulf’s immense natural capacity to break down oil. Then there was the response mounted by BP and the government, the largest in history, involving more than 4,000 boats attacking the oil with skimming equipment, controlled surface burns and other tactics.
It was also becoming clear that the Obama administration, in conjunction with BP, will soon have to make decisions about how quickly to begin scaling down the large-scale — and expensive — response effort. That is a touchy issue, and not just for environmental reasons.
States have been pushing the federal authorities to move quickly to reopen gulf waters to commercial fishing; through most of the spill, about a third of the United States part of the gulf has been closed. The Food and Drug Administration is trying to speed its testing, while promising continued diligence to be sure no tainted seafood gets to market.
Even if the seafood of the gulf is deemed safe by the authorities, resistance to buying it may linger among the public, an uncertainty that defies measurement and is on the minds of residents along the entire Gulf Coast.
