

How Science Stopped BP's Gulf of Mexico Oil Spill

Remote imaging of the failed blowout preventer, stress testing various containment devices as well as other high-tech tasks helped contain the Deepwater Horizon disaster

U.S. Senate Committee on Environment and Public Works

Forty-eight hours into an attempt to muscle a gusher of oil back into the deep-sea well from which it spewed, the flow of petroleum and gas refused to slow. Screen after screen in a special room at BP's headquarters in Houston showed the oil gushing undiminished, silently witnessed underwater by remotely operated vehicles (ROVs).

The room—called the HIVE, for Highly Immersive Visualization Environment—was hardly the only place at BP buzzing with activity. Earlier, locked in the 10-meter-square "intervention room" on the third floor, scientist fought scientist in the battle over whether to proceed with an established way to plug the leak, the so-called "top kill" operation. Nobel Prize winning physicist and U.S. Secretary of Energy Steven Chu remained unconvinced of BP's technical case, whereas geologist by training Tony Hayward, CEO of the British oil major, felt it had as much as a 70 percent chance of success, according to the President's National Commission on the BP Deepwater Horizon Oil Spill and Offshore Drilling report released in January.

That might have been true had the oil been flowing at the rate BP and the U.S. National Oceanic and Atmospheric Administration (NOAA) estimated, roughly 5,000 barrels per day. (One barrel of petroleum holds about 160 liters.) In fact, such top kills had worked to control other wells in the past, albeit not those some 1,500 meters beneath the ocean surface. But, perhaps unknown to BP at the time, the oil was gushing at more than 50,000 barrels per day—meaning it had plenty of pressure to blow top-kill mud back out of the hole.

The scientist-versus-scientist clashes are just some of the new details about science's role in stopping the spill that have emerged in the year since the Deepwater Horizon drilling rig exploded and set off what would become the worst oil spill in U.S. history. When BP scientists couldn't figure out how the blowout preventer failed, Chu suggested gamma-ray imaging, which could visually pierce the giant piece of equipment at the bottom of the sea. (It did the trick, revealing that the preventer's pipe-shearing rams had not fully slammed shut, allowing oil to continue spewing.) When BP engineers presented plans for containment caps or other operations, Chu and his team of independent hydrologists and geophysicists would question assumptions in a bid to force BP to consider the full range of possibilities, rather than simply hoping for the best. And when BP scientists failed to develop better plans, Chu invited other oil companies—Chevron, ExxonMobil and Shell—into the effort.

"Where the limits of reality lay"
The entry of Secretary Chu and a team of government scientists—pulled from the U.S. Department of Defense's JASON independent advisory group—began May 10, three weeks after the blast that killed 11 workers. At that time, they were there only to assist BP as it struggled to regain control of its well on the Gulf of Mexico seafloor. BP had dubbed the well Macondo for the ill-starred, fictional town in Gabriel Garcia Marquez's One Hundred Years of Solitude. "It was as if God had decided to put to the test every capacity for surprise and was keeping the inhabitants of Macondo in a permanent alternation between excitement and disappointment, doubt and revelation, to such an extreme that no one knew for certain where the limits of reality lay," as Garcia Marquez wrote—words that could be equally applied to the gushing deep sea oil well.

The passage also aptly described the situation faced by the scientists at BP, such as vice president of engineering Paul Tooms or vice president and engineer Richard Lynch, who seemed incapable of determining how much oil was actually flowing and figuring out how to stop it despite valiant efforts. An early attempt born of the "containment room" ultimately created and submerged a nearly disastrous underwater balloon—albeit a solid steel balloon four-stories high and weighing nearly 100 metric tons—that became buoyant when methane-filled ice formed beneath the giant dome meant to enclose the well. The structure instead floated up toward rescue boats on the surface. Had attempts to steer it away on May 7 failed, a collision between a ship and the methane-containing steel balloon could have caused a conflagration as bad as the explosion that ultimately destroyed the Deepwater Horizon. Plus, this cofferdam effort preempted an ROV effort using sonar and acoustic sensors that would have more precisely measured the flow of oil and natural gas into the sea.

In the "intervention room," explicitly charged with messing with the well itself, the pressure was perhaps higher than at the wellhead. The converted training room had become something akin to NASA's Mission Control, the conditions at the bottom of the Gulf as hostile to humans and human efforts as the vacuum of space. Cables wrapped in yellow tape snaked down from the ceiling, sprawling onto the white laminated tables where they plugged scientists' laptop computers into grids of electricity and information grids. Diagrams of blowout-halting technology and maps of the Gulf served as wallpaper.

On the afternoon of May 26, BP technicians fired up pumps rated at a total of 30,000 horsepower and began shooting heavy drilling mud into the well. In addition, the BP team fired "junk shots"—a mix of golf balls, rubber balls and other detritus—in a bid to slow the oil flow. A BP technician read off pressure readings to those in the intervention room: 8,000 pounds per square inch; 7,000 pounds per square inch; 6,000 pounds per square inch (psi). Initial signs seemed good as BP ramped up the flow rate of mud to as much 70 barrels per minute.

But the ROV camera impassively showed the mud spewing back out of the well and onto the seafloor. The shredded balls in the junk shots were not clotting the flow of oil, and it was visible for all to see on the live video feed.

Chu versus the oil volcano
There is something of the owl in Chu's heart-shaped face—giving the impression of proverbial wisdom but also of a veiled raptor, ready to strike the intellectually unprepared. He may look oddly casual with his hands nestled in the pockets of the dark blue power suits he favors in Washington, D.C., but he attacks with questions. Even in the simple collared shirt with rolled-up sleeves that he favored for his time in Houston, the bespectacled Energy secretary posed a danger to the oil company scientists and executives, especially as he quickly acquired knowledge about the problem posed by Macondo. The only question was: Whose scientific expertise would prevail?

Secretary Chu could be forgiven for possibly feeling conflicted about his role: He had been called in to save an industry, while working as hard as he could to render it obsolete via programs like the Advanced Research Projects Agency–Energy. If energy could be personified, Chu would be among those who immediately come to mind, dashing from one global event to another—from the high-profile climate summit in Copenhagen to the prosaic opening of a solar factory in the U.S. Midwest—all as he penned peer-reviewed research for major journals and tended to his day-to-day political responsibilities.

Now he had to cope with a wild, seemingly unstoppable gusher in conditions that had no precedent. The pressure readings the technician was calling out stopped dropping at roughly 6,000 psi, meaning that the flowing oil was successfully pushing back against the pump engine's 30,000 horsepower. The pressure readings just wouldn't drop—even when BP tried again with denser mud.

By May 27, it had become clear to even its main supporters like Tony Hayward that the top-kill attempt had failed. And by the end of the weekend, BP had new overseers. Chu killed top kill on May 28, worried that BP's efforts would cause a subsurface blowout and make the gusher impossible to control.

By mid-June, Chu wrote an e-mail to his team, including physicist Richard Garwin, who had helped invent the hydrogen bomb as well as cap burning oil wells after the Persian Gulf War, and Tom Hunter, former director of Sandia National Laboratories in New Mexico. Quoting Gregory Peck in The Guns of Navarone, Chu wrote: "Your bystanding days are over! You're in it now, up to your neck! They told me that you're a genius with explosives. Start proving it!" Of course, Chu quickly noted that explosives—despite calls for the U.S. Navy to bomb the well shut, with nukes if necessary—were not likely to be useful "on this mission…the rest rings true."

What finally worked
Despite Chu's oversight, BP remained in charge of critical information flowing from the deep-sea blowout. Chu's team had to know what to ask for and request it specifically in order to get their hands on data. The government scientists got enough information to give their blessing to BP's "top hat" approach, which—taking a lesson from the failed cofferdam—boasted circulating methanol to prevent methane-filled ice from forming. By June 3, the top hat was capturing roughly 15,000 barrels a day—or three times early estimates, and the upper threshold after which BP's Tooms had calculated "top kill" would fail—with no discernible impact on the flow of oil into the ocean.

Even when BP began pumping oil and gas through a line from the blowout preventer to the Q4000 well-servicing ship—at Garwin's suggestion—the flow of oil into the sea remained undiminished. The Q4000, which had pumped the mud for top kill, had specially designed flares for oil and gas that enabled BP to burn off as much as 10,000 barrels a day—bringing the total amount of oil prevented from flowing into the sea to as much as 25,000 barrels a day at times. Because this containment still failed to show any visible improvement in the amount of oil flowing from the wellhead, Secretary Chu's back-of-the-e-mail math suggested that at least 40,000 barrels a day must be gushing from the well.

What finally worked on July 12 was a smaller blowout preventer installed atop the failed blowout preventer at the well's head on the seafloor, replacing the top hat. This "capping stack" had risks, however, such as creating the kind of subsurface blowout that would end up draining all the estimated 110 million barrels of oil in the entire formation. But government scientists calculated the flow would have to be 100,000 barrels per day—or nearly twice as much as it actually was (roughly 50,000 barrels per day)—for that risk to be realized.

Once the cap was in place, BP prepared to conduct a "well integrity test"—essentially, shutting off the flow of oil and checking pressure readings to see if a subsurface blowout would develop. In the worst case a burst of methane could liquefy and collapse the seafloor surrounding the wellhead, thereby swallowing the blow-out preventer, capping stack and all. In a frantic, overnight session the government scientists assessed that risk and, by morning, they had decided such a worst-case blowout could be prevented with early detection of a leak.

So Chu and his colleagues required BP to monitor the well's pressure continuously for the 48 hours of the test and to keep tabs on the blowout preventer, the well itself, and the underground regions around it through both acoustic and visual methods offered by two of the 12 ROVs as well as a NOAA survey ship. Should a leak of more than 20,000 barrels be detected, or if oil pressure fell below 6,000 psi—implying an underground leak that could prove catastrophic—the cap would be immediately removed.

On July 15 at 2:25 P.M. Houston time, the test began. An ROV arm turned the handle on the capping stack 10 times, cranking it closed. For the first time since April 20, no oil spewed into the Gulf of Mexico.

Is it over yet?
The pressure of the well hovered around 6,600 psi, prompting Garwin, among others, to argue for the immediate removal of the cap.

Instead, a cell phone picture of the pressure readings graph was sent to hydrologist Paul Hsieh of the U.S. Geological Survey in Menlo Park, Calif. Working through the night, Hsieh determined that, in his best modeling estimate, the relatively low pressure readings were not a result of subsurface cracks or leaks developing but rather the fact that so much oil had already spewed from the well. Its original internal pressure of roughly 13,000 psi had diminished. The cap would stay closed.

With the oil staunched, Chu allowed BP to proceed with a so-called "static kill"—another attempt to push the oil back down the well with heavy drilling mud, made much easier by the fact that the oil no longer had a clear path out of the seafloor. Drilling mud went into the well again on August 3, followed on August 4 by a 1.5 kilometer-long cement plug.

In the end, however, despite all the resources of the federal government and one of the world's largest corporations, only a second well drilled at an angle and roughly five kilometers beneath the seafloor finally intercepted the base of the Macondo well and safely sealed the reservoir with cement. The first such relief well began drilling on May 2 and reached pay dirt in the third week of September, along with a second relief well that commenced drilling on May 17—at the insistence of U.S. Secretary of the Interior Ken Salazar. "Our job basically is to keep the boot on the neck of British Petroleum," the former senator from Colorado said on CNN.

On September 19, U.S. Coast Guard Admiral Thad Allen—national incident commander for the blowout—declared that "the Macondo 252 well is effectively dead" after spilling roughly five million barrels of oil in total.

What didn't die with it is America's thirst for oil: The U.S. consumes 21 million barrels daily. As a result of that thirst, BP has asked the federal government for permission to resume deepwater drilling in the Gulf. And, until the world's use of approximately one barrel of oil per second diminishes, it is unlikely that the Macondo blowout will follow the fate of Garcia Marquez's fictional town and be "exiled from the memory of man."

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