On Tuesday, Bloomberg News reported that federal prosecutors are considering filing manslaughter charges against BP managers in the April 20, 2010, deaths of 11 crewmembers of the drilling rig Deepwater Horizon. BP, which has already paid billions of dollars to help clean up the largest accidental oil spill in history and compensate those who suffered economic losses, has been under the threat of criminal indictments since June. To date, the blame for the well blowout has been widely distributed, with BP deflecting much, if not most, of the responsibility for the disaster to the companies the oil company had hired to drill and manage their well. An indictment of BP managers for manslaughter would be a dramatic refutation of that position. To meet the legal definition of manslaughter, those responsible for the safe drilling of the well would have to be found to have acted with negligence, "without due caution and circumspection."
If the government has a case against BP managers, it is most likely related to decisions made in the final stages of well construction, designed to ensure that the well shaft was safely sealed off from the highly pressurized and potentially explosive oil and gas deposit 18,000 feet below the ocean's surface. What follows is a timeline of those decisions, drawn from thousands of pages of sworn testimony.
Early April 2010
After two months of drilling a troublesome well code-named Macondo, an effort marred by walls that kept crumbling and dangerously unexpected bubbles of natural gas pushing into the well shaft, the crew of the BP-leased rig Deepwater Horizon finally reaches a large hydrocarbon deposit—the lake of oil and gas trapped under high pressure in sponge-like sandstone that was their primary objective. As they drill deeper, toward a second deposit just below it, the unstable formation gives way again, allowing roughly a million dollars worth of drilling fluid to leak into the surrounding rock before the well could be patched. BP managers opt to surrender rather than risk more losses. They abandon attempts to reach the deeper oil deposit and decide to finish off the well where it is, sealing it with a final section of pipe, then encasing the pipe in cement.
Running a computer simulation on the eve of Macondo's final cement job, Haliburton engineer Jesse Gagliano, on contract to BP, gets an unpleasant surprise. After putting all the known variables into the modeling program, the computer spits out a severe verdict: The cement job is likely to fail, allowing highly pressurized gas to force its way into the well and threaten a blowout. Gagliano races down the hall of BP's Houston headquarters to huddle with his BP counterparts. After hours, they craft a solution—a more elaborate and expensive well design that will create multiple layers of protection against gas flow if the cement job fails. Almost as soon as the new plan is submitted, BP higher-ups reject it, as too expensive and time consuming. They instruct the engineers to make the original, less-expensive design work. The engineers huddle again and come up with a compromise plan that they believe will ensure an effective cement job that will safely seal the well. The key to their plan involves the use of a large number of spacing devices that fit around the outside of the final length of pipe. The spacers, called centralizers, push out against the well wall to keep the pipe perfectly centered within, allowing the cement to flow evenly, reducing the likelihood that air channels will form, as happens when a pipe leans too closely against one side of the well wall. The number of centralizers the computer indicates they need to prevent this is 21. Even with that many, the engineers know there's still a chance the plan won't succeed, which is not a risk they feel they can take. They add to their plan an expensive post-cement-job test to make sure the centralizers worked.
When Brian Morel, a BP engineer in place on the Deepwater Horizon, hears about the idea of increasing the number of centralizers, he emails back to Houston: "We have 6 centralizers [on board], we can run them in a row, spread out, or any combination of the two. It's a vertical hole, so hopefully the pipe stays centralized due to gravity. As far as changes, it's too late to get any more product on the rig, our only option is to rearrange placement of these centralizers."
Greg Walz, one of the BP engineers who had been working with Gagliano, is concerned enough about the computer-predicted consequences of using only six centralizers that he gets on the phone to locate the additional 15 centralizers himself, and arranges for them to be flown out to the Horizon in time for the cement job. Walz sends a memo to his boss, BP's Macondo well team leader John Guide, telling him what he's done, adding, "We need to honor the modeling to be consistent with our previous decisions to go with the long string."
Guide messages back that he thinks, wrongly, it turns out, that the centralizers Walz procured are the wrong kind. In any case, Guide writes, "It will take 10 hrs to install them. I do not like this and … I [am] very concerned about using them."
The decision: Do the job with the original six centralizers.
As the bottom cement job is about to begin, Jimmy Harrel, Transocean's senior man on the Horizon, learns of BP's plan to use a light nitrogen-foamed cement to avoid pushing out the fragile well walls again. He vehemently objects. He points out that high pressures of the deep can force the nitrogen out and cause cement failure. The BP company men aboard the rig insist. The Transocean manager acquiesces, not knowing that in tests a few days earlier, the nitrogen cement had not proven to be stable under conditions similar to what would be expected at the bottom of the well. The cement job goes forward as planned.
April 20 12:36 a.m.
The cement job is completed. The crew waits for the cement to set.
The expensive test to insure that the cement has sealed the well recommended by cement engineer Gagliano is deemed unnecessary. Contractors waiting on the rig to perform the test are sent home on a helicopter, saving BP $118,000 and half a day.
The Horizon's pumps begin to suck out the heavy drilling mud that has filled the well shaft for months, preventing natural gas from forcing to the surface and causing a blowout. The mud is replaced with much lighter seawater, deemed safe now that the cement is thought to have sealed the well.
As the protective weight of the mud disappears, gas begins to flow into the well, most likely due to failure of the cement job.
The last of the drilling fluid is displaced from the well. Inside the well, the pressure begins to rise.
Undetected by the crew, the gas, expanding rapidly now, shoots up past the blowout preventer into the pipe that rises from the sea floor to the derrick.
As the gas explodes to the surface, a column of water and mud pushed ahead of it bursts up through the derrick, then splatters the rig in a rain of mud.
Now realizing that the well is starting to blow, tool pusher Jason Anderson attempts to close the seals on the blowout preventer. The blowout preventer, overwhelmed by the force of the upwelling gas, fails to close-in the well.
Gas escapes on to the rig in a loud, hissing rush.
The main engines, fed by the cloud of methane gas, race into overspeed, tripping the breakers. The rig loses power.
Something, possibly a spark from a racing engine, ignites the gas. An explosion rips through the engine room. Seconds later, another explosion ignites a fireball on the drill floor and blowing off the rear of the rig, including two of the four lifeboats. Ten men working on the rig floor, including Jason Anderson, are likely killed instantly. The port crane operator is knocked by the blast from his crane to the deck, either dies from his injuries or burns to death in the fire.
A muster of survivors who have evacuated to a rescue boat confirms that 11 people have not made it to safety. There are 17 injured.
April 21 10:22 p.m.
The Horizon, still burning and top heavy from hundreds of thousands of gallons of water and fire retardant poured onto it, topples into the Gulf of Mexico and sinks to the bottom. As it sinks, the pipe connecting the Horizon to the well severs. The oil and gas, still gushing out of the well at the rate of more than two million gallons a day, begins to pour into the ocean.
The timeline is adapted from Fire on the Horizon: The Untold Story of the Gulf Oil Disaster, published by HarperCollins.
Tom Shroder was an editor and writer at The Washington Post from 1999 to 2009. Under his stewardship, stories in The Washington Post Magazine won the Pulitzer Prize for feature writing in both 2008 and 2010. He is the author of the nonfiction bestseller Old Souls. He lives in Vienna, Virginia.