Originally Released November 22, 2010

Updated January 11, 2011

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National Commission on the BP Deepwater Horizon Oil Spill and Offshore Drilling

STOPPING THE SPILL: THE FIVE-MONTH EFFORT TO KILL THE MACONDO WELL

Staff Working Paper No. 6

Staff working papers are written by the staff of the National Commission on the BP Deepwater 

Horizon Oil Spill and Offshore Drilling for the use of members of the Commission. They do not 

necessarily reflect the views of the Commission or any of its members. In addition, they may be 

based in part on confidential interviews with government and non-government personnel. 

The effort to contain and control the blowout of the Macondo well was unprecedented. 

From April 20, 2010, the day the well blew out, until September 19, 2010, when the government

finally declared it “dead,” BP expended enormous resources to develop and deploy new 

technologies that eventually captured a substantial amount of oil at the source and, after 87 days, 

stopped the flow of oil into the Gulf of Mexico. The government organized a team of scientists 

and engineers, who took a crash course in petroleum engineering and, over time, were able to 

provide substantive oversight of BP, in combination with the Coast Guard and the Minerals 

Management Service (MMS).1 BP had to construct novel devices, and the government had to 

mobilize personnel on the fly, because neither was ready for a disaster of this nature in 

deepwater.

The containment story thus contains two parallel threads. First, on April 20, the oil and

gas industry was unprepared to respond to a deepwater blowout, and the federal government was 

similarly unprepared to provide meaningful supervision. Second, in a compressed timeframe, 

BP was able to design, build, and use new containment technologies, while the federal 

government was able to develop effective oversight capacity. Those impressive efforts, 

however, were made necessary by the failure to anticipate a subsea blowout in the first place.

Both industry and government must build on knowledge acquired during the Deepwater Horizon 

spill to ensure that such a failure of planning does not recur.

I. Emergency Response to the Blowout

Following the explosion on the Deepwater Horizon during the evening of April 20, 2010, 

while firefighting efforts were underway at the surface, Transocean and BP began working 

subsea to stop the flow of hydrocarbons from the Macondo well. Almost immediately, they 

started assessing the status of the 53-foot-tall blowout preventer (“BOP”) stack, which stood atop 

the well.2 

 

1 On June 18, 2010, Secretary of the Interior Ken Salazar ordered that the Minerals Management Service be 

officially renamed the Bureau of Ocean Energy Management, Regulation, and Enforcement. For consistency, 

throughout this paper, we will refer to the agency as the Minerals Management Service (MMS), its name at the time 

of the April 20, 2010 blowout. 

2 Non-public Transocean document; Non-public BP document; Henry Fountain, Focus Turns to Well-Blocking 

System, N.Y. TIMES (May 10, 2010).
Originally Released November 22, 2010

Updated January 11, 2011

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The Macondo well tapped into a reservoir more than 13,000 feet below the sea floor, 

containing roughly 110 million barrels of oil.3 Extending upwards from the reservoir to the sea 

floor was a steel pipe called the “production casing.” During production, this pipe was to contain

the “production tubing,” which would convey oil from the reservoir up to a vessel on the surface. 

The production casing was surrounded by other casings, which are integral to the drilling process 

and provide barriers between the production casing and the rock formation surrounding the well.4 

Each gap between casings, or between the outermost casing and the rock formation, is called an 

annulus. 

The production casing hung off a “casing hanger” in the “wellhead,” or top of the well. 

The wellhead is a large, steel fitting that sits on the sea floor. Above the wellhead was the BOP 

stack. The drilling rig on the ocean’s surface—the Deepwater Horizon—connected to the stack 

5,000 feet below through a long steel pipe called a “riser.” During drilling operations, the drill 

pipe (which has a bit at its end) passed from the rig through the riser and BOP stack, then down 

into the well.

Figure 1.A: Above the Sea Floor (Not to Scale)5

 

3

Interview with government scientist.

4 The bottom 1,136 feet of the production casing in the Macondo well was not surrounded by an outer casing, 

leaving it exposed to the reservoir.

5

Image provided by BP.
Originally Released November 22, 2010

Updated January 11, 2011

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Figure 1.B: Below the Sea Floor (Not to Scale)

A BOP stack is both integral to the drilling process and—as its name suggests—the last 

line of defense in preventing a blowout. The lower portion of the stack is often referred to 

simply as the BOP. The BOP on the Macondo well contained five separate closing devices, 

called “rams.” The five rams were designed to serve different functions: for example, cutting 

drill pipe or casing, or sealing around drill pipe while leaving it intact. The “blind shear ram” 

was the only ram of the five with the ability to cut through drill pipe and completely shut in the 

well. In addition to the rams, the BOP had “boost,” “choke,” and “kill” lines, which were used

to circulate fluids into and out of the well. 

The top portion of the BOP stack is called the “lower marine riser package.” On the 

Macondo well, that package contained two additional sealing mechanisms, called “annular 

preventers.” Each preventer includes a hard rubber device in the shape of a tire that is designed 

to expand and seal around drill pipe or else seal the well entirely if drill pipe is not present.

BP’s earliest containment efforts, undertaken with Transocean, focused on trying to close 

the rams and annular preventers within the BOP stack using remotely operated vehicles.6 There

are some indications that, even at this stage, BP was concerned about “well integrity”—i.e., the 

possibility that oil was flowing outside the production casing, and could flow sideways out of the 

 

6 Non-public Transocean document; Non-public BP document; Henry Fountain, Focus Turns to Well-Blocking 

System. Before evacuating following the explosion on the evening of April 20, the Deepwater Horizon’s crew had 

attempted to actuate the BOP stack and seal off the well. An ongoing forensic analysis of the BOP stack may fully 

explain the results of the crew’s actions. For purposes of this paper, it is sufficient to recognize that the crew’s 

efforts did not stop the flow of hydrocarbons.
Originally Released November 22, 2010

Updated January 11, 2011

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well and into the rock formation if the well were shut in. According to Billy Stringfellow, a 

Transocean Subsea Superintendent, BP delayed interventions with remotely operated vehicles 

for approximately 20 hours in part because it was concerned that the pressure created by closing 

the BOP stack and shutting in the well might force hydrocarbons into the surrounding rock and 

“create an underground blowout.”7 Some of that delay may also be attributable to concerns 

about positioning surface ships operating the vehicles too close to the fire then consuming the 

Deepwater Horizon rig.8 Remotely operated vehicles began working on the BOP stack at about 

6:00pm on April 21.9 The rig sank approximately sixteen hours later, on the morning of April 

22.10

The earliest operations on the BOP primarily attempted to activate the blind shear ram.11 

During those attempts, officials from MMS were embedded in the operations centers at 

Transocean and BP headquarters in Houston. Those officials described themselves as observers, 

with on-scene personnel from BP, Transocean, and Cameron (the company that manufactured 

the BOP stack) making decisions.12 According to the officials, there was no need for 

government approval of the early attempts on the BOP because of the ongoing emergency and 

because MMS was generally familiar and comfortable with the operations.13 Starting on April 

21, Secretary of the Interior Ken Salazar also received daily updates on source control activities 

through conference calls with BP’s technical teams.14 These calls would continue throughout the 

containment effort.15

Initially, the news was good: On April 23, Federal On-Scene Coordinator Admiral Mary 

Landry stated that, according to surveillance by remotely operated vehicles, the BOP stack, while 

“[i]t is not a guarantee,” appeared to have done its job, sealing off the flow of hydrocarbons and 

preventing any leak.16 That same day, senior management from BP, Transocean, Cameron, and 

Wild Well Control, a contractor to BP specializing in blowouts, met and concluded that, with 

 

7 Testimony of Billy Stringfellow, Transocean, COAST GUARD/BOEM MARINE BOARD OF INVESTIGATION INTO THE 

MARINE CASUALTY, EXPLOSION, FIRE, POLLUTION, AND SINKING OF MOBILE OFFSHORE DRILLING UNIT DEEPWATER 

HORIZON [hereinafter COAST GUARD/BOEM BOARD OF INVESTIGATION] 408, 423-24 (Aug. 25, 2010).

8

See Testimony of Daun Winslow, Transocean, COAST GUARD/BOEM BOARD OF INVESTIGATION 51-53 (Aug. 24, 

2010) (discussing risk mitigation strategies employed to get ships close to the wellhead using water cannon 

curtains); Harry R. Weber, Contractor: BP Interfered with Critical Efforts, ASSOCIATED PRESS (Oct. 4, 2010) 

(describing precautions BP took to ensure that surface ships would not be harmed by the fire consuming the rig).

9 Non-public Transocean document; Non-public BP document.

10 Non-public Transocean document; Non-public BP document.

11 Non-public BP document. On April 22, remotely operated vehicles tried to activate the blind shear ram in three 

separate ways: (1) by providing hydraulic pressure to the ram through the BOP’s “hot stab” panel, which was 

specifically designed to be accessed by remotely operated vehicles; (2) by simulating the “Deadman,” which was 

supposed to automatically actuate the ram if electric, hydraulic, and communication connections with the Deepwater 

Horizon were lost; and (3) by cutting the firing pin for the “Autoshear,” which was designed to actuate the ram if the 

rig drifted out of position and disconnected the lower marine riser package from the BOP. Id; David Barstow et al., 

Regulators Failed to Address Risks in Oil Rig Fail-Safe Device, N.Y. TIMES (June 20, 2010); Testimony of Mark 

Hay, Transocean, COAST GUARD/BOEM BOARD OF INVESTIGATION 292 (Aug. 25, 2010).

12 Interviews with MMS officials.

13 Interview with MMS official.

14 Non-public government document.

15 Id.

16 Leslie Kaufman, Search Ends for Missing Oil Rig Workers, N.Y. TIMES (Apr. 23 2010); see also Angel Gonzalez 

and Stephen Power, Coast Guard Says Oil Leak Stopped, WALL ST. J. (Apr. 24, 2010).
Originally Released November 22, 2010

Updated January 11, 2011

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regard to the BOP stack, “[w]e have to take a noninvasive approach and not broach/risk what we 

have now in regards to stability of the well.”17 By mid-afternoon on April 23, however, remotely 

operated vehicles had discovered that oil was leaking from the end of the riser, which had broken 

off from the rig when it sank.18 By the next morning, the vehicles had also discovered a second 

leak from a kink in the riser, located above the BOP stack.19

II. Early Containment Efforts

As it became clear that the initial efforts to actuate the BOP stack had been unsuccessful 

and that there were two separate leaks from the riser, BP began to consider other source control 

options. As early as April 21, BP started to discuss drilling a relief well to intersect the Macondo 

well at its source and stop the flow of oil.20 Doug Suttles, Chief Operating Officer for 

Exploration and Production at BP, characterized a relief well as a standard industry technique for 

stopping a blowout, but said he believed at the time of the blowout that the drilling would take 

approximately 100 days.21 Several experts from both industry and government described relief 

wells to Commission staff as the only accepted, high-probability solution to a subsea blowout, 

even though they take months to drill.22 A relief well was the only source control option 

mentioned by name in BP’s Initial Exploration Plan for the area that included the Macondo 

well.23 Within days of the explosion, BP mobilized two rigs to drill separate relief wells, a 

primary well and a back-up insisted upon by Secretary Salazar.

24

 After an expedited MMS 

permitting process, the first rig began drilling on May 2,25 with the second beginning on May 

17.26

Other than the lengthy process of drilling a relief well, BP had no available, tested 

technique to stop a deepwater blowout. Less than a week after the explosion, it embarked on 

what would become a massive effort to develop containment options, either by adapting shallowwater technology to the deepwater environment, or by designing entirely new devices. Different 

teams at BP’s Houston headquarters focused on different ways either to stop the flow of oil or to 

collect it at the source.

27

 Each team concentrated on a discrete containment effort, like actuating 

the BOP stack, developing near-term options to collect oil from the riser, or stopping the flow 

through a “top kill” procedure.28 Each team also had what amounted to a blank check. As one 

contractor put it, “Whatever you needed, you got it. If you needed something from a machine 

 

17 Henry Fountain, Notes from Wake of Blowout Outline Obstacles and Frustration, N.Y. TIMES (June 21, 2010).

18 Non-public Transocean document.

19 Non-public government document; Campbell Robertson, Oil Leaking Underwater from Well in Rig Blast, N.Y.

TIMES (Apr. 24, 2010).

20 Non-public government document.

21 Interview with Doug Suttles, Houston, TX (Oct. 13, 2010).

22 Interviews with MMS officials; Interview with well control expert.

23 BP, INITIAL EXPLORATION PLAN, MISSISSIPPI CANYON BLOCK 252 (Feb. 23, 2009), 

http://www.gomr.boemre.gov/PI/PDFImages/PLANS/29/29977.pdf.

24 Non-public government document.

25 BP Press Release, Work Begins To Drill Relief Well To Stop Oil Spill (May 4, 2010), 

http://www.bp.com/genericarticle.do?categoryId=2012968&contentId=7061778.

26 The White House, Ongoing Response Timeline (May 17, 2010), 

http://www.whitehouse.gov/blog/2010/05/05/ongoing-administration-wide-response-deepwater-bp-oil-spill.

27 Interview with Doug Suttles.

28 Interview with Richard Lynch, Houston, TX (Oct. 13, 2010).
Originally Released November 22, 2010

Updated January 11, 2011

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shop and you couldn’t jump in line, you bought the machine shop.”29 Several MMS officials 

agreed that, for BP, money was no object: If a team needed equipment, whether it was a ship, 

freestanding riser, or flexible hose, BP would buy it.30 As Suttles pointed out, BP’s parallel 

processing effort required enormous resources, and the size of its presence in the Gulf of Mexico 

was a big advantage.31

BP also sought help and advice from the oil and gas industry. One well control expert 

recalled a meeting in early May with at least 35 people, including representatives from the four 

companies in the world that specialize in well control; BP’s major competitors, including 

ConocoPhillips, Exxon, and Shell; and academic petroleum engineering departments.

32

 The 

expert remembered BP forthrightly admitting that it was seeking all of the help it could get.33 

According to Suttles of BP, nearly everyone in the industry recognized the magnitude of the 

emergency and answered BP’s calls for assistance.

34

MMS was the primary source of government oversight and expertise on source control 

operations, with the Coast Guard overseeing surface operations, vessel safety, and firefighting 

preparedness.35 BP drafted detailed procedures describing the operation it wished to perform 

around the wellhead. MMS and Coast Guard officials in Houston participated in the drafting 

process to help identify and mitigate hazards. Once the procedures were finalized, the officials 

in Houston would approve and forward them to the Unified Area Command in Louisiana.36 At 

Unified Command, Lars Herbst, MMS Gulf of Mexico Regional Director, or his deputy, Mike 

Saucier, would again review and approve the procedures, before the Federal On-Scene 

Coordinator, a Coast Guard Admiral, gave the final go-ahead.37 This sign-off process remained 

in place throughout the containment effort.

MMS was the sole government agency charged with understanding deepwater wells and 

related technology, such as BOP stacks. Its supervision of the containment effort, however, was 

limited, in line with its established role in overseeing deepwater drilling more generally. Its staff 

did not attempt to dictate whether BP should perform an operation, to suggest consideration of 

other options, or to determine whether an operation had a significant likelihood of success.38 

Rather, MMS focused on minimizing the safety risks of operations BP proposed and ensuring 

conformity with MMS regulations.39 In part, MMS’s limited role stemmed from a lack of

resources. At most, MMS had four to five employees in Houston trying to oversee BP’s 

efforts.40 One employee described his experience as akin to standing in a hurricane.41 Despite 

 

29 Interview with well control expert.

30 Interviews with MMS officials.

31 Interview with Doug Suttles.

32 Interview with well control expert.

33 Id.

34 Interview with Doug Suttles.

35 Interviews with Coast Guard officials.

36 Interviews with MMS officials.

37 Interviews with MMS officials.

38 Interview with Coast Guard official; Interview with MMS official.

39 Interviews with MMS officials.

40 Interview with MMS official.

41 Interview with MMS official.
Originally Released November 22, 2010

Updated January 11, 2011

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working more than 80 hours a week, this individual recalled having to miss more than half of the 

BP engineering team meetings he was supposed to attend each day.42

These resource constraints, however, do not fully explain MMS’s role. Interviews of 

MMS staffers involved in the containment effort suggest that the agency viewed itself as neither 

capable of, nor tasked with, providing more substantive oversight. One MMS employee asserted 

that BP, and industry more broadly, possessed ten times the expertise that MMS could bring to 

bear on the enormously complex problem of deepwater containment.43 Another pointed out that 

MMS has trouble attracting the most talented personnel, who are more likely to work in industry 

where salaries are substantially higher.44 A third MMS employee stated that he could count on 

one hand the people from the agency whom he would trust to make key decisions in a source 

control effort of this magnitude.45 Perhaps most revealingly, two MMS employees recalled highlevel officials at the Department of the Interior asking what they would do if the U.S. 

Government took over the containment effort. Both said they would hire one of the major oil 

companies.

46

It was in this environment—with BP deploying in-house and outside industry expertise to 

develop a containment strategy, while MMS and the Coast Guard provided limited procedural 

supervision—that the early containment efforts moved forward. 

A. Attempts To Actuate the Blowout Preventer Stack

Even though the initial efforts had failed, BP thought that actuating the BOP stack 

remained its best chance to shut in the well quickly. After a two-day pause, BP restarted the 

attempts on April 25. It enlisted the help of other oil companies, including Shell, Exxon, 

Chevron, and Anadarko.47 None of the attempts, however, stopped the flow of oil. Although 

several focused again on the blind shear ram, others were directed at different rams and at the 

annular preventers in the BOP stack, which were not designed to shut in the well completely 

where—as here—drill pipe was present. It appears that BP and Transocean were trying to use 

the BOP stack to reduce the flow of hydrocarbons, even if they were unable to stop the flow 

altogether.48

 

42 Id.

43 Id.

44 Interview with MMS official.

45 Interview with MMS official.

46 Interviews with MMS officials.

47 Guy Chazan, BP Seeks Help from Other Oil Companies, WALL ST. J. (May 1, 2010).

48 Non-public BP document; see, e.g., Clifford Krauss, Overhead and on the Ground, Waiting for a Potential 

Environmental Disaster to Hit, N.Y. TIMES (Apr. 30, 2010) (quoting Suttles as indicating that one outcome of 

closing the annular preventer was “substantially reduc[ing] the flow of oil.”). 
Originally Released November 22, 2010

Updated January 11, 2011

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Efforts to actuate the BOP stack were plagued by engineering and organizational 

problems. For instance, it took nearly ten days for a Transocean representative to realize that the 

stack’s plumbing was not as it seemed and to inform the engineers attempting to actuate one of 

the BOP’s rams through a “hot stab” panel that they had been misdirecting their efforts.49 

Without properly recording the change, Transocean had reconfigured the BOP stack; the panel 

that was supposed to control that ram actually operated a different, “test” ram, which was not 

designed to stop the flow of hydrocarbons from the well.

50

 BP Vice-President Harry Thierens, 

who was BP’s lead on BOP interventions, stated afterwards that he was “quite frankly astonished 

that this could have happened.”51 In contemporaneous notes, he wrote: “When I heard this 

news, I lost all faith in this BOP stack plumbing.”52 The inability of on-scene remotely operated 

vehicles to deliver enough hydraulic pressure may also have hindered attempts to close the 

rams.

53

 At the very least, these problems delayed the closure efforts, while high-pressure 

hydrocarbons and sand wore down the BOP stack’s components, making closure more 

difficult.54

In its accident report, BP indicated that it ceased trying to close the BOP stack on May 

5.55 By May 7, BP had concluded that “[t]he possibility of closing the BOP has now been 

essentially exhausted.”56 At the time, BP believed that various portions of the BOP had 

functioned: One ram had successfully severed the drill pipe, one or more of the other rams had 

closed, and the blind shear ram had partially closed, but not sealed the well.57 

BP undertook gamma-ray imaging of the BOP stack, proposed by Secretary of Energy 

Steven Chu, in mid-May.58 Although the imaging suggested that the blind shear ram had at least 

partially closed,59 hydrocarbons continued to flow past it. According to BP’s accident report, the 

blind shear ram could have failed to seal the well for a number of reasons, including the presence 

of a joint connecting two pieces of drill pipe where the ram attempted to make its cut, 

insufficient hydraulic pressure due to leaks in the stack, or degradation of the rams due to 

hydrocarbon flow and pressure conditions.60 In September, BP retrieved the BOP stack from the 

sea floor.

61 The Coast Guard and MMS hired the Norwegian firm Det Norske Veritas to perform 

 

49 Testimony of Harry Thierens, BP, COAST GUARD/BOEM BOARD OF INVESTIGATION 104 (Aug. 25, 2010).

50 Fountain, Notes from Wake of Blowout Outline Obstacles and Frustration; Non-public BP document.

51 Testimony of Harry Thierens, BP, COAST GUARD/BOEM BOARD OF INVESTIGATION at 106.

52 Id. at 107.

53 David Barstow et al., Between Blast and Spill, One Last, Flawed Hope, N.Y. TIMES (June 21, 2010); BP,

DEEPWATER HORIZON ACCIDENT INVESTIGATION REPORT 169-71 (Sept. 8, 2010); Testimony of Billy Stringfellow, 

Transocean, COAST GUARD/BOEM BOARD OF INVESTIGATION at 397-99.

54 Non-public government science advisor email. Billy Stringfellow of Transocean recently testified: “I think it’s a 

well-known fact throughout the industry that abrasives can damage BOP components. . . . The quickest reaction time 

you can get is what you’re looking for.” Testimony of Billy Stringfellow, COAST GUARD/BOEM BOARD OF 

INVESTIGATION at 352.

55 BP, DEEPWATER HORIZON ACCIDENT INVESTIGATION REPORT at 150.

56 Non-public BP document.

57 Id. 

58 Barstow et al., Regulators Failed to Address Risks in Oil Rig Fail-Safe Device; John M. Broder, Energy Secretary 

Emerges To Take a Commanding Role in Effort To Corral Well, N.Y. TIMES (July 16, 2010).

59 Barstow et al., Regulators Failed to Address Risks in Oil Rig Fail-Safe Device.

60 BP, DEEPWATER HORIZON ACCIDENT INVESTIGATION REPORT at 156-60.

61 Blowout Preventer May Hold Clues to Oil Spill, CBS NEWS (Sept. 5, 2010).
Originally Released November 22, 2010

Updated January 11, 2011

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forensic analysis, which may answer the question of why the Deepwater Horizon’s BOP stack 

failed to seal the well.

B. Cofferdam

On April 25, as efforts to actuate the BOP stack continued, BP began to consider placing 

a large containment dome, also known as a cofferdam, over the larger of the two leaks from the 

broken riser.62 At the top of the cofferdam, a pipe would channel hydrocarbons to the 

Discoverer Enterprise, a ship on the surface.63 Although some initial reports indicated that BP 

would need as long as four weeks to install the dome,64 BP was able to move more rapidly. It

already had several cofferdams, which it had used to provide safe working space for divers 

repairing leaks from shallow-water wells following Hurricanes Katrina and Rita.65 By May 4, 

just ten days after first raising the possibility of using a containment dome, BP reported that it 

had finished modifying for deep-sea use and oil collection a preexisting dome that was 14 feet 

wide, 24 feet long, and 40 feet tall.66 Following an MMS inspection of the Discoverer 

Enterprise,

67 BP began to lower the 98-ton dome to the sea floor late in the evening of May 6

(see Figure 2).

68

 BP planned to stage a second cofferdam on the sea floor in case the first dam 

failed.69

 

62 Non-public government document; Campbell Robertson and Leslie Kaufman, Oil Leaks Could Take Months To 

Stop, N.Y. TIMES (Apr. 25, 2010). On April 28, BP discovered a third leak, located closer to the source than the 

kink leak. See Campbell Robertson and Leslie Kaufman, Size of Spill in Gulf of Mexico is Larger than Thought, 

N.Y. TIMES (Apr. 28, 2010). While BP was able to quickly stop that leak with a specially designed valve, this action 

did not reduce the amount of oil being released. See Sam Dolnick and Liz Robbins, BP Says One Oil Leak of Three 

Is Shut Off, N.Y. TIMES (May 5, 2010).

63 Sam Dolnick and Henry Fountain, Unable to Stanch Oil, BP Will Try To Gather It, N.Y. TIMES (May 5, 2010); 

BP Press Release, Work Begins To Drill Relief Well To Stop Oil Spill (May 4, 2010), 

http://www.bp.com/genericarticle.do?categoryId=2012968&contentId=7061778.

64 Guy Chazan and Ben Casselman, Documents Show BP Opposed New, Stricter Safety Rules, WALL ST. J. (Apr. 28, 

2010); Ben Casselman, Stephen Power, and Ana Campoy, Oil-Spill Fight Bogs Down, WALL ST. J. (Apr. 30, 2010).

65 Interview with Richard Lynch; Interview with Doug Suttles.

66 Interview with Richard Lynch; BP Press Release, Work Begins To Drill Relief Well To Stop Oil Spill.

67 The White House, The Ongoing Administration-Wide Response to the Deepwater BP Oil Spill (May 6, 2010), 

http://www.whitehouse.gov/blog/2010/05/05/ongoing-administration-wide-response-deepwater-bp-oil-spill.

68 Deepwater Team Attempts To Put 100-Tonne Box over Blown-out Well, GUARDIAN (May 7, 2010).

69 Non-public government document; Interview with Richard Lynch.
Originally Released November 22, 2010

Updated January 11, 2011

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Figure 270

From the beginning, the likelihood of collecting hydrocarbons with the cofferdam was 

uncertain. Suttles of BP publicly cautioned that a containment dome had only been used 

successfully in much shallower water.71 In an interview, he told Commission staff that, 

according to BP engineers, the chance of success was at best 50 percent.72 Bob Fryar, a senior 

BP engineer, warned, “This is new technology. . . . It has never been done before.”73 BP 

recognized that chief among the potential problems was the risk that methane gas escaping from 

the well would come into contact with sea water and form slushy hydrates, essentially clogging 

the cofferdam with hydrocarbon ice. BP planned to mitigate this concern once the dome had 

been installed by circulating warm water into the dome from the surface, so that hydrocarbons 

could flow up the riser unimpeded.74 Notwithstanding these uncertainties, BP, in a presentation 

to the leadership of the Department of the Interior, described the probability of the cofferdam’s 

success as “Medium/High.”75 Others in the oil and gas industry were not so optimistic: Experts 

have told Commission staff that it was widely understood within the industry that the cofferdam 

effort was very likely to fail due to hydrate formation.76

 

70 Image provided by BP.

71 Ian Urbina, Justin Gillis, and Clifford Krauss, On Defensive, BP Readies Dome to Contain Spill, N.Y. TIMES

(May 3, 2010).

72 Interview with Doug Suttles.

73 Dolnick and Fountain, Unable to Stanch Oil, BP Will Try To Gather It.

74 Non-public BP document.

75 Id.

76 Interview with well control expert; Interview with drilling expert.
Originally Released November 22, 2010

Updated January 11, 2011

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BP’s effort to capture oil from the Macondo well with the containment dome did not

succeed. While BP had a plan to deal with hydrates once the cofferdam was in place, it had not 

planned to mitigate hydrate formation during the installation process itself.77 When crews started 

to maneuver the cofferdam over the leak at the end of the riser on the evening of May 7, hydrates 

formed before the dam could be put in place, clogging the opening through which oil was to be 

funneled.78 BP Vice President Richard Lynch, who oversaw the cofferdam effort, told 

Commission staff that BP did not anticipate hydrates forming this early.79 Because hydrocarbons

are lighter than water, the containment dome became buoyant as it filled with oil and gas while 

BP tried to lower it.

80

 In the New York Times, Lynch recalled engineers telling him that they had 

“lost the cofferdam,” which, after filling with highly flammable material, had begun floating up 

toward the ship-covered ocean surface.81 Engineers were eventually able to gain control of the 

98-ton dome and move it to safety on the sea floor.82 One high-level government official 

recalled Andy Inglis, BP’s Chief Executive of Exploration & Production, saying “if we had tried 

to make a hydrate collection contraption, we couldn’t have done a better job.”83

The lack of an accurate flow-rate estimate may have hindered BP’s planning for the 

cofferdam. Suttles told Commission staff that, at the time BP deployed the cofferdam, no one at 

BP believed the flow of oil was greater than 13-14,000 barrels per day (bbls/day).

84

 The 

government’s then-current estimate of the flow rate was 5,000 bbls/day,85 an order of magnitude 

lower than its now-current estimate of the flow in early May (approximately 60,000 bbls/day).86 

Government officials have told Commission staff that part of the reason for the quicker-thanexpected formation of hydrates in the cofferdam was the large flow volume.87

 Moreover, BP had 

publicly predicted that the cofferdam would remove about 85% of the oil spilling into the sea.88 

But the ship BP planned to connect to the cofferdam, the Discoverer Enterprise, was capable of 

 

77 Interview with Richard Lynch.

78 Campbell Robertson, New Setback in Attempt to Contain Gulf Oil Spill, N.Y. TIMES (May 8, 2010).

79 Interview with Richard Lynch.

80 Id.

81 Clifford Krauss, Henry Fountain, and John M. Broder, Acrimony Behind the Scenes of Gulf Oil Spill, N.Y. TIMES 

(Aug. 26, 2010).

82 Id.

83 Interview with senior administration official.

84 Interview with Doug Suttles.

85 On April 28, the government announced a flow rate estimate of 5,000 bbls/day. Press Conference, Admiral Mary 

Landry and Doug Suttles, New Orleans, LA (Apr. 28, 2010), 

http://cgvi.uscg.mil/media/main.php?g2_itemId=843309. This remained the government’s official estimate until 

May 27. Unified Command Press Release, Flow Rate Group Provides Preliminary Best Estimate of Oil Flowing 

from BP Oil Well (May 27, 2010), http://app.restorethegulf.gov/release/2010/05/27/flow-rate-group-providespreliminary-best-estimate-oil-flowing-bp-oil-well. 

86 See Deepwater Horizon Incident Joint Information Center Press Release, U.S. Scientific Teams Refine Estimates 

of Oil Flow from BP’s Well Prior to Capping (Aug. 2, 2010), http://app.restorethegulf.gov/release/2010/08/02/usscientific-teams-refine-estimates-oil-flow-bps-well-prior-capping. While BP has not released its own flow-rate 

estimates, it has suggested that the government’s estimate of the total amount of oil released from the Macondo 

well—4.9 million barrels—is overstated by 20 to 50%. Meeting with BP, Washington, D.C. (Oct. 22, 2010).

87 Interview with senior administration official; Interview with MMS official; see also Interview with well control 

expert.

88 Dolnick and Fountain, Unable to Stanch Oil, BP Will Try To Gather It.
Originally Released November 22, 2010

Updated January 11, 2011

- 12 -

processing a maximum of 15,000 bbls/day.89 If even half of the government’s now-estimated 

60,000 bbls/day was then flowing, the containment dome could not have collected 85% of the oil 

from the Macondo well, putting aside the issue of hydrates. 

It is unclear whether a more accurate sense of the cofferdam’s likelihood of success 

would have enabled BP to proceed differently. At the time, other containment options had not 

yet been developed, and the cofferdam did not risk damaging the well or otherwise making the 

spill worse. Several BP executives indicated that the Discoverer Enterprise was the only 

collection ship available, suggesting that a better understanding of the flow volume would not

have resulted in more processing capacity for the operation.90 Nonetheless, BP modeled hydrate 

formation and assessed the cofferdam’s collection abilities without an accurate estimate of the oil 

flow.

Government oversight of the cofferdam operation was similar to oversight of efforts to 

actuate the BOP stack. MMS and the Coast Guard formally approved proposed procedures, after 

working with BP to identify operational hazards.91 Government officials did not substantively

review BP’s plan to mitigate hydrate formation or evaluate BP’s predictions as to the 

cofferdam’s likelihood of success.92 More robust oversight, addressing such strategic and 

scientific issues, would not begin until late May.93 

C. Riser Insertion Tube Tool

Following the failure of the cofferdam, BP began, on May 14, trying to install a smaller 

device termed the Riser Insertion Tube Tool (RITT) into the end of the broken riser, the site of 

the primary leak.94 After two days of attempts and some modifications, BP installed the tool on 

May 16.95 The tool was a four-inch-diameter tube that fit into the end of the riser and carried oil 

and gas up to the Discoverer Enterprise on the surface a mile above. According to Lynch, BP 

was able to avoid a buildup of hydrates because the tool was inserted far enough into the riser to

only pull in oil and gas, rather than mixing hydrocarbons with seawater.

96

 Over the nine days of 

 

89 See Clifford Krauss and Michael Cooper, Cap Slows Gulf Oil Leak as Engineers Move Cautiously, N.Y. TIMES

(June 5, 2010).

90 Interview with Richard Lynch; Interview with Doug Suttles; Interview with Paul Tooms, Houston, TX (Oct. 13, 

2010).

91 Interviews with MMS officials.

92 Interview with MMS official; Interviews with government science advisors; Interview with senior administration 

official.

93 Interview with senior administration official; Interview with government scientist.

94 Non-public government document.

95 Non-public government document.

96 Interview with Richard Lynch.
Originally Released November 22, 2010

Updated January 11, 2011

- 13 -

use, the riser insertion tool was able to collect approximately 22,000 barrels of oil.

97

 BP 

executives had different recollections of the tool’s highest instantaneous collection rate, ranging 

up to 12,000 bbls/day.98 

Data from the riser insertion tool indicated that the flow rate was greater than the highest 

instantaneous collection rates. For the entire time the tool was in place, visible hydrocarbons 

were still escaping around it at the end of the riser.

99

 Hydrocarbons were also still flowing from 

the second, smaller leak at the kink in the riser.100 

BP could have expanded its capacity to collect hydrocarbons from the riser. It deployed 

additional riser insertion tools to the sea floor by May 23.

101

 According to Lynch, these tools 

had a larger diameter and would have had greater collection capacity than the first.102 BP did not 

use these extra tools because another source control operation that it had been planning 

simultaneously, the “top kill,” was about to begin. 

III. The Arrival of the National Labs and Science Advisory Teams, the Top Kill 

and Junk Shot, and the Move to Collection

The failure of the cofferdam seemed to highlight the shortage of viable options to control 

the Macondo well. Somewhat outlandish suggestions filled the void. For instance, in mid-May, 

a Russian newspaper suggested detonating a nuclear weapon deep within the well to seal off the 

flow of oil, as the former Soviet Union had done on a number of occasions.103

Perhaps prompted by the cofferdam’s failure, the federal government increased its 

footprint in Houston. Facilitated by Deputy Secretary of the Interior David Hayes, scientists and 

engineers from three Department of Energy National Laboratories had started to help BP obtain 

diagnostic information about the well and BOP stack in early May.

104

 National labs personnel 

would remain on site at BP headquarters for the remainder of the containment effort. On May 7, 

 

97 Methods that Have Been Tried to Stop the Leak, N.Y. TIMES (Aug. 17, 2010), 

http://www.nytimes.com/interactive/2010/05/25/us/20100525-topkill-diagram.html.

98 Interview with Richard Lynch (recalling a rate of 12,000 bbls/day); Interview with Paul Tooms (recalling a rate of 

8,000 to 10,000 bbls/day). The government’s Flow Rate Technical Group, in its May 27 press release, noted that 

“[o]n May 25, 2010, at approximately 17:30 CDT, the [riser insertion tool] logged oil collection at a rate of 8,000 

barrels of oil per day, as measured by a meter whose calibration was verified by a third-party.” Deepwater Horizon 

Incident Joint Information Center Press Release, Flow Rate Group Provides Preliminary Best Estimate of Oil 

Flowing From BP Oil Well (May 27, 2010), http://app.restorethegulf.gov/release/2010/05/27/flow-rate-groupprovides-preliminary-best-estimate-oil-flowing-bp-oil-well.

99 Interview with Richard Lynch; Interview with Paul Tooms.

100 Meeting with BP (Oct. 22, 2010).

101 Non-public government document.

102 Interview with Richard Lynch.

103 Jeremy Hsu, Why Don’t We Just Drop a Nuclear Bomb on the Gulf Oil Spill?, CHRISTIAN SCIENCE MONITOR

(May 13, 2010).

104 Non-public government document; U.S. Department of Energy Press Release, Secretary Salazar and Secretary 

Chu To Meet with Scientists and Engineers at BP Houston Command Center (May 11, 2010), 

http://www.energy.gov/news/8976.htm; Interview with government scientist; Interview with senior administration 

official. The three national laboratories involved were Sandia National Laboratories, Los Alamos National 

Laboratory, and Lawrence Livermore National Laboratory. In Houston, this group was sometimes called the “trilabs team.”
Originally Released November 22, 2010

Updated January 11, 2011

- 14 -

Secretary Salazar asked Dr. Marcia McNutt, the Director of the U.S. Geological Survey who had 

traveled with him to the Gulf on May 4, to remain in Houston to oversee source control 

efforts.105 Finally, on May 10, President Obama directed Secretary Chu to form a team of 

government officials and scientists to work with BP on source control.106 On May 11, Secretary 

Chu called several prominent scientists and asked them to join him the next day for a 6:30am

meeting with BP in Houston.107

The May 12 meeting signified the beginning of an oversight role for Secretary Chu and 

his team of science advisors. A winner of the 1997 Nobel Prize for Physics, Secretary Chu had 

been the Director of Lawrence Berkeley National Laboratory, where he focused on renewable 

energy technologies and atomic physics.108 Secretary Chu’s principal deputy for the containment 

effort was Dr. Tom Hunter, who arrived in Houston in early May and was about to retire from 

his position as Director of Sandia National Laboratories, where he had worked for 43 years, 

primarily on the nuclear weapons program.109 Along with Dr. McNutt, Dr. Hunter served as a 

link between the on-site national labs personnel and Secretary Chu’s science advisory team.

The advisory team included well-known scientists and engineers. Some, but not all, had 

prior oil and gas experience. For instance, Dr. Alexander Slocum, an MIT professor, holds more 

than sixty patents and had done some work on drilling design.110 Dr. George Cooper had been 

the head of the Petroleum Engineering Program at the University of California at Berkeley and is 

a Senior Petroleum Engineer at Lawrence Berkeley National Laboratory.111 Dr. Arun Majumdar 

is the Director of the Department of Energy’s Advanced Research Project Agency—Energy.

112

 

Dr. Richard Garwin, who helped design the world’s first hydrogen bomb, was involved in 

putting out the Kuwaiti oil fires following the first Gulf War.113 Although the team members 

attended the May 12 meeting in person, the vast majority of their future participation in decisionmaking occurred via conference calls.114

The role of both the national labs personnel and Secretary Chu’s advisory team took time 

to evolve from helping BP diagnose the situation to providing substantive oversight on 

containment. In part, this was because the Secretary of Energy, his team of advisors, and the 

national labs lacked a formal role within the Unified Command structure.115 Their oversight was 

 

105 U.S. Department of Energy Press Release, Secretary Salazar and Secretary Chu To Meet with Scientists and 

Engineers at BP Houston Command Center; Interview with senior administration official.

106 U.S. Department of Energy Press Release, Secretary Salazar and Secretary Chu To Meet with Scientists and 

Engineers at BP Houston Command Center.

107 Interviews with government science advisors.

108 Bio, Secretary Steven Chu, Department of Energy, http://www.energy.gov/organization/dr_steven_chu.htm.

109 Press Release, NNSA Honors Tom Hunter, Welcomes Paul Hommert as Director of Sandia Labs (May 13, 2010); 

Interview with government science advisor.

110 Curriculum Vitae, Dr. Alexander Slocum, http://meche.mit.edu/documents/slocum_CV.pdf; Interview with 

government science advisor.

111 Faculty Biography, George A. Cooper, University of California, Berkeley, 

http://www.ce.berkeley.edu/faculty/faculty_bio.php?name=Cooper/.

112 Bio, Dr. Arun Majumdar, ARPA—E, http://arpa-e.energy.gov/About/Team/DrArunMajumdar.aspx.

113 William J. Broad, Physicist and Rebel is Bruised, Not Beaten, N.Y. TIMES (Oct. 8, 1999); Interview with 

government science advisor.

114 Interviews with government science advisors. 

115 Interview with Coast Guard official.
Originally Released November 22, 2010

Updated January 11, 2011

- 15 -

grafted onto the existing framework, which required MMS and the Coast Guard to sign off on 

BP’s proposals. It also took some time for the national labs team to integrate itself into the 

command structure led by MMS and the Coast Guard. While MMS, the Coast Guard, and Dr. 

McNutt worked out of offices on the third floor of BP’s Houston headquarters, the national labs 

team sat on the eighteenth floor.116 One MMS staffer who was in Houston from late April 

through early July told Commission staff that he never interacted with the national labs team: 

They never reached out to him, and he had no idea on what they were working.117 Perhaps as a 

result of these unclear lines of authority, BP’s provision of data to the government was 

uneven.118 Although BP gave information when asked, it did not proactively share, so 

government officials had to know what information they were seeking and ask for it 

specifically.119 By mid-June, the government teams created a process by which the national labs 

engineers and science advisors could direct formal requests for information and action to BP.120

Finally, both the science advisors and the national labs team had to educate themselves 

on the situation, and on deepwater petroleum engineering more generally, before they could 

participate substantively in decision-making.121 Thus, in mid-May, while the science advisors 

were learning the lay of the land, the national labs engineers focused on helping BP obtain 

diagnostic information through efforts such as gamma-ray imaging of the BOP stack.122 

Meanwhile, throughout May, BP set the strategy for trying to control the well, with limited 

government oversight.123

While the government science teams were getting up to speed over the course of May, BP 

was ramping up for its first major effort to stop the flow from the Macondo well: the “top kill” 

and “junk shot.”

A. Top Kill and Junk Shot

Top kills and junk shots are standard industry procedures for stopping the flow of 

hydrocarbons from a blown-out well,

124 though they had never been used in deepwater.125

 Also 

 

116 Interview with Coast Guard official; Interviews with MMS officials; Interview with Paul Tooms.

117 Interview with MMS official.

118 Interview with senior administration official; Interview with Coast Guard official; Interview with government 

science advisor.

119 Interview with senior administration official.

120 Interview with government scientist.

121 Interview with government scientist; Interview with government science advisor.

122 Interview with government scientist; Interview with government science advisor.

123 Non-public government document; Interviews with government science advisor; Interview with senior 

administration official.

124 Interview with well control expert.
Originally Released November 22, 2010

Updated January 11, 2011

- 16 -

known as a momentum or dynamic kill, a top kill involves pumping heavy drilling mud into the 

top of a well through the BOP’s choke and kill lines, at rates and pressures significant enough to 

force escaping hydrocarbons back down the well and into the reservoir. A junk shot 

complements a top kill. It involves pumping bridging materials—including pieces of tire rubber 

and golf balls—into the bottom of a BOP through the choke and kill lines. Those bridging 

materials ideally get caught on obstructions in the flow path for hydrocarbons—such as pieces of 

drill pipe and partially deployed BOP rams—and further impede the flow. By slowing or 

stopping the flow of hydrocarbons, a successful junk shot makes it easier to execute a top kill.

BP’s top kill team began its work in the immediate aftermath of the initial failed efforts to 

actuate the BOP stack.

126

 Leading up to the operation, both BP and federal engineers modeled 

different scenarios based on different rates at which oil might be flowing from the Macondo 

well. Paul Tooms, BP’s Vice President of Engineering, told Commission staff that BP hired a 

Norwegian company to model different outcomes depending on the flow rate of hydrocarbons.127 

He recalled that, given the planned pumping rates, the top kill was unlikely to succeed with oil 

flow rates greater than 15,000 bbls/day.128 National labs engineers modeled the top kill based on 

the then-current flow-rate estimate of 5,000 bbls/day, concluding that mud would need to be 

pumped at greater than 20 barrels per minute to succeed.129 Yet, surprisingly, a well control 

contractor involved in the top kill effort told Commission staff that the flow rate was not a factor 

in designing the top kill procedure or determining its likely success. According to this 

contractor, the top kill’s likelihood of success depended on the area through which hydrocarbons 

flowed from the well, but would have been the same if the flow rate were only 10 bbls/day, 

instead of the actual rate.130 Commission staff did not speak to anyone else in government or 

industry who shared this view.

Nonetheless, a senior administration official recalled being told by a BP engineer, on the 

day the operation began, that the top kill would not work if the flow rate was greater than 13,000 

bbls/day.

131

 The official responded that a government team was about to come out with a new 

flow-rate estimate with a lower bound of 12,000 to 25,000 bbls/day.132 BP’s engineer replied 

that there could be some margin above 13,000 bbls/day at which the top kill might succeed.133 In 

retrospect, according to the government official, if BP had devoted a fraction of the resources it 

expended on the top kill to obtaining a more accurate early estimate of the flow rate, it might 

have better focused its efforts on the containment strategies that were more likely to succeed.134

 

125 BP, COMMENTS ON NOVEMBER 22, 2010 VERSION OF DRAFT STAFF WORKING PAPER NO. 6 (Dec. 10, 2010); see

Campbell Robertson, Clifford Krauss, and John M. Broder, Oil Hits Home, Spreading Arc of Frustration, N.Y.

TIMES (May 24, 2010) (citing Suttles).

126 Interview with well control expert; Interview with Richard Lynch.

127 Interview with Paul Tooms.

128 Id. This estimate was apparently based on a mud pumping rate of 40-45 barrels per minute. In addition, a 

successful junk shot would have obstructed the flow path and reduced the flow rate. It therefore could have enabled 

the top kill to succeed even if the initial flow rate were greater than 15,000 bbls/day.

129 Non-public government documents.

130 Interview with well control expert.

131 Interviews with senior administration official.

132 Interview with senior administration official.

133 Id.

134 Id.
Originally Released November 22, 2010

Updated January 11, 2011

- 17 -

While the government had limited involvement in planning the top kill procedure, the 

science advisors had expressed concerns about the junk shot, both because junk could get stuck 

in the well and block the mud from pushing hydrocarbons back into the reservoir, and because 

junk could increase the pressure in and stress on the well and BOP stack.135 Suttles of BP 

suggested that junk also had the potential to clog the choke and kill lines, which could interfere 

with future source control operations.136 In the early morning of May 25, the day before the 

three-day top kill operation began, Tom Knox of BP assured the government science advisors, 

including Secretary Chu, that “[t]he junk shot is no longer on the flow sheet. It is not an option 

under consideration.”137 At some point, however, the junk shot was put back on the table, 

because BP did attempt it. Tooms suggested that this change was made after the failure of the 

initial top kill effort, which involved only mud (not junk).138

With the approval of Coast Guard Admiral Landry, the Federal On-Scene Coordinator, 

the top kill began on the afternoon of May 26.139 Secretary Chu and some members of his 

science team were in the command center in Houston.140 The top kill operation consisted of 

three separate attempts on three consecutive days. First, BP attempted to pump only mud at rates 

of up to 53 barrels per minute or more than 76,000 bbls/day.141 Although initially pressures 

within the well began to drop, suggesting that hydrocarbons were potentially being pushed back 

into the reservoir, the pressure readings soon flattened out, indicating that the top kill was not 

making further progress.

142

After a pause to analyze the results, BP made a second attempt on May 27, pumping mud 

at 25 barrels per minute or 36,000 bbls/day and firing fifteen different junk shots of bridging 

materials.143 Again, the effort did not succeed. After another pause for analysis, BP undertook a 

third and final attempt on May 28. On that day, BP pumped mud at rates up to 80 barrels per 

minute or more than 115,000 bbls/day and fired two junk shots of bridging materials.144 Even 

pumping at these higher rates, BP did not succeed. While Secretary Chu evidently had the 

authority to call off the top kill at his discretion,

145 members of the science advisory team and BP 

executives recall that both BP and the government agreed to stop the top kill, concluding that it 

would not work after the failure of the third attempt.146

BP struggled with public communications surrounding the top kill effort. Internally, both 

BP and government officials were uncertain about the odds of success. Tooms recalled that, 

when Secretary Salazar asked a group of individuals who worked on the top kill about its 

 

135 Non-public government science advisor emails.

136 Interview with Doug Suttles.

137 Non-public government science advisor email.

138 Interview with Paul Tooms.

139 The White House Blog: Deepwater Horizon Oil Spill (May 26, 2010), 

http://www.whitehouse.gov/blog/issues/Deepwater-BP-Oil-Spill?page=6.

140 Interview with government science advisor.

141 Non-public BP document.

142 Interview with Doug Suttles.

143 Non-public BP document.

144 Id.; Interview with MMS official.

145 Interview with government science advisor.

146 Interview with government science advisor; Interview with Doug Suttles; Interview with Paul Tooms.
Originally Released November 22, 2010

Updated January 11, 2011

- 18 -

likelihood of success, most said 70%.147 One MMS employee involved in the procedure told 

Commission staff that, at the time, he estimated the chance of success as less than 50%.148 

Finally, a BP contractor who participated in the operation told Commission staff that, going into

the top kill, he gave it a “tiny” chance to succeed.149 Notwithstanding this uncertainty, BP CEO 

Tony Hayward stated publicly that “[w]e [BP] rate the probability of success between 60 and 70 

percent.”150 Suttles told Commission staff that he was careful not to predict the top kill’s chance 

of success and did not know what led Hayward to do so.151

B. Top Kill Analysis

Immediately following the top kill, BP teams in Houston met throughout the night of 

May 28 to assess the operation.152 Some meetings occurred behind closed doors, without 

government participation. At one point, Lars Herbst of MMS and Coast Guard Admiral Kevin 

Cook, who had been dispatched by National Incident Commander Admiral Thad Allen to be his 

representative in Houston, entered a meeting and stated that they had a right to be present.153 

Apparently, government officials had not previously insisted on joining these types of meetings, 

and BP personnel were surprised by the interruption.154 Asserting the right to be present for

BP’s top kill analysis was a turning point for the government team. After the failure of the top 

kill, the government significantly increased its oversight of the containment effort.155

Following the overnight meeting on the top kill, BP presented its assessment of why the 

operation failed. Understanding that analysis requires a brief digression on the Macondo well’s 

design and, specifically, on the presence of “rupture disks” in the 16”-diameter casing within the 

well.156 The 16” casing is the longest piece of pipe outside of the production casing. It forms the 

outermost barrier between the well and the rock formation for more than 1,000 vertical feet at 

approximately 10,000 feet below sea level.157 The casing was purposely fabricated with three 

sets of failure points, called rupture disks. Those disks were designed to relieve pressure buildup 

resulting from heat during production, before that buildup could cause a collapse of the 

production casing or the 16” casing itself.

The disks were engineered to rupture in two separate ways. First, if pressure between the 

16” casing and the production casing reached 7,500 pounds per square inch (psi)—less than the 

11,140 psi at which the production casing would collapse—the rupture disks would burst

 

147 Interview with Paul Tooms.

148 Interview with MMS official.

149 Interview with well control expert.

150 Robertson, Krauss, and Broder, Oil Hits Home, Spreading Arc of Frustration.

151 Interview with Doug Suttles.

152 Interview with Paul Tooms.

153 Interviews government officials.

154 Interview with government official.

155 Interview with government science advisor; Interview with senior administration official.

156 Technically, the 16” pipe is a “liner” rather than a “casing,” because it hangs 160 feet below the wellhead. 

Casing runs all the way up to the wellhead, where it hangs from a “casing hanger.” A liner does not run all the way 

up to the wellhead, and instead hangs from a “liner hanger” placed further down in the well. For simplicity’s sake, 

and because individuals in the oil and gas industry often use the terms interchangeably, we nevertheless refer to the 

16” pipe as a “casing.” 

157 Macondo Well Schematic. 
Originally Released November 22, 2010

Updated January 11, 2011

- 19 -

outward.

158

 Second, if pressure outside of the 16” casing topped 1,600 psi—less than the 2,340 

psi at which the 16” casing would collapse—the rupture disks would collapse inward.

159

 Once 

ruptured, the disks would create small holes in the 16” casing to bleed off pressure into the 

surrounding rock formation.160

Figure 3

 

158 Non-public BP document.

159 Id.

160 Non-public BP document.
Originally Released November 22, 2010

Updated January 11, 2011

- 20 -

According to BP’s analysis, several factors, including the pressures observed during the 

top kill attempt—initially dropping, then flat-lining—made it plausible that the rupture disks in 

the 16” casing had collapsed inward during the initial blowout.

161

 If the blowout had resulted in 

flow of hydrocarbons up the annulus between the 16” casing and the production casing, the 

difference in pressure between the heavy drilling mud that remained outside the 16” casing from 

the drilling process and the light hydrocarbons within could have been greater than the 1,600 psi

at which the rupture disks would collapse inward.

162

 At the time, BP concluded that the top kill 

likely failed because mud pumped down the well had gone out through the collapsed rupture 

disks and sideways into the rock formation, rather than remaining within the well and pushing 

the hydrocarbons back into the reservoir, as had been intended.

163

 Based on a comparison of 

pressure readings across the three top kill attempts, as well as visual observation,

164 BP believed 

that it had pumped more mud down into the well during the top kill than had come back up. If 

that were true, the mud had to have traveled either all the way down to the bottom of the well, or 

through the rupture disks and out of the sides of the well into the rock formation.165

Although Tooms of BP emphasized to Commission staff that collapse of the rupture disks 

was one of several plausible theories to explain the results of the top kill,166 BP presented it to 

the government as the most likely scenario, and found its likelihood sufficient to change strategy 

moving forward.167 The government teams did not challenge the assumption that BP had 

pumped more mud into the well than had flowed back out, but they were skeptical of BP’s 

analysis regarding where the mud went during the top kill.168 The national labs team performed 

its own analysis and concluded that only a fraction of the mud pumped during the top kill could 

have escaped into the rock formation through the rupture disks.169 The team found it more likely 

that mud had gone down the production casing and into the rock formation at the bottom of the 

well.170 This scenario could also explain the top kill’s failure, as follows: While mud traveled

down the central production casing, hydrocarbons continued to flow up the annulus outside of 

the production casing, into the BOP, and out of the riser.

171

 

Although the government and BP analyzed the flow of mud during the top kill 

differently, the government believed that BP’s hypothesis of collapsed rupture disks was 

plausible, and that well integrity needed to be considered moving forward.172 In retrospect, 

several members of the government science teams have told Commission staff that a more likely 

cause of the top kill’s failure was the flow rate, which was many times greater than 5,000 

 

161 Interview with Paul Tooms; Non-public BP document.

162 Non-public BP document.

163 Interview with Coast Guard official; Interview with MMS official; Interview with senior administration official.

164 Non-public government document; Non-public BP documents.

165 Interview with government scientist.

166 Interview with Paul Tooms.

167 Interview with Coast Guard official; Interview with MMS official; Interview with senior administration official.

168 Interview with government scientist.

169 Interview with senior administration official; Interview with government scientist; Non-public government 

document.

170 Interview with government scientist; Non-public government document.

171 Non-public government document.

172 Interview with senior administration official.
Originally Released November 22, 2010

Updated January 11, 2011

- 21 -

bbls/day, the government’s official estimate when the top kill commenced.

173

 Because BP did 

not pump mud into the well at high enough rates to counter the actual flow, the hydrocarbons 

flowing from the well ejected the mud back up the BOP stack and out of the riser.174 

Prior to the top kill, in separate presentations to Secretary Chu and Secretary Salazar, BP

had indicated that, if the top kill failed, its next step might be to cut the riser, remove the lower 

marine riser package, and install a second BOP on top of the existing BOP to shut in the well.

175

 

The theorized collapse of the rupture disks, however, took capping the well off the table. If BP 

shut the well in and hydrocarbons were flowing up the annulus between the production and 16” 

casings—as would have been necessary to cause the rupture disks to collapse during the 

blowout—the hydrocarbons in this annulus would follow the path of least resistance. They 

would flow out the rupture disks and into the rock formation in what is called a “broach” or 

“underground blowout.” From there, the hydrocarbons could rise through the layers of rock and 

into the ocean. Containment of hydrocarbons flowing directly from the sea floor, rather than 

from a single source like the top of a well, is nearly impossible. With BP emphasizing the 

possible collapse of the rupture disks and risk of broach, shutting in the well—via a second BOP 

or otherwise—was deemed not viable.

176

 In the aftermath of the top kill, BP and the government 

therefore directed their efforts toward collecting the oil, rather than closing the well, with the 

relief wells still providing the most reliable avenue for killing the well completely.177

C. A Move to Collection

i. The Build-Out of Capacity

Because it had been developing multiple containment options in parallel, BP had a team 

ready to proceed with new collection efforts almost immediately.178 On May 29, BP and the 

government announced that BP would attempt to cut off the portion of the riser still attached to 

the BOP stack and install a collection device in its place.

179

 Like the riser insertion tool and the 

 

173 Interviews with government scientists; Interview with government science advisor; Interview with senior 

administration official.

174 Interviews with government scientists; Interview with government science advisor; Interview with senior 

administration official.

175 Non-public BP documents; see also BP, ANSWERS TO FOLLOW-UP QUESTIONS POSED BY PRESIDENTIAL 

COMMISSION STAFF (Nov. 2, 2010).

176 Non-public BP documents; Interview with Doug Suttles. One government official told Commission staff that 

another concern with installing a second BOP was weight: The existing BOP stack was listing at 2 degrees from 

vertical, and there was a risk that adding weight to its top would lead to further damage or collapse. Interview with 

senior administration official.

177 Non-public BP document; Interview with senior administration official; Interview with Doug Suttles.

178 Interview with Richard Lynch.

179 Ongoing Administration-Wide Response to the Deepwater BP Oil Spill (May 29, 2010), 

http://www.restorethegulf.gov/release/2010/05/29/ongoing-administration-wide-response-deepwater-bp-oil-spill; BP 
Originally Released November 22, 2010

Updated January 11, 2011

- 22 -

cofferdam, this new cap or “top hat” was to be connected via a riser to the Discoverer Enterprise

on the surface.180 To be prepared for different possible connection points, BP had, by this time,

constructed seven different top hats.181

The top hat installation was largely successful. On June 1, BP used, through remotely 

operated vehicles, large hydraulic shears to cut the riser at a small distance from the top of the 

BOP stack.

182

 On June 2, BP deployed a diamond riser saw, which was designed to cut the

remaining portion of the riser more cleanly and closer to the top of the BOP stack. The saw, 

however, became stuck in the riser. BP then used the hydraulic shears to make a more jagged cut 

in the same area.183 By 11:00pm on June 3, the top hat was in place and siphoning hydrocarbons 

to the surface.184 BP had learned from its cofferdam experience and used methanol injections to 

prevent formation of hydrates within the top hat.185 By June 8, the Discoverer Enterprise was 

collecting nearly 15,000 bbls/day of oil through the top hat.186

As the top hat collection system ramped up, BP was also developing a system to bring 

hydrocarbons to the surface through the choke line on the BOP, which BP had used to pump mud

and junk during the top kill. Following the top kill, BP began to outfit the Q4000, a vessel 

involved in the top kill effort, with equipment including an oil and gas burner brought from 

France.187 After some subsea build-out and testing, the Q4000 system became operational just 

before 10:00pm on June 16.188 Once up and running, the Q4000 was able to process and burn, 

rather than collect, up to 10,000 bbls/day of oil through the choke line.189

The final collection system that BP was able to deploy was the Helix Producer, a 

production ship that connected to the kill line on the BOP through a freestanding riser. The 

freestanding riser had the advantage of requiring less disconnect and reconnect time than the top 

hat and Q4000 in case of a hurricane.190 It was a key addition to BP’s collection capacity, which 

BP envisioned would eventually reach 90,000 bbls/day of oil.

191

 BP began building the first 

freestanding riser system on May 15, and began building a second on June 7 in order to expand 

its collection capacity.

192

 Nevertheless, the Helix Producer only became operational on July 

 

Press Release, Update on Gulf of Mexico Oil Spill (May 29, 2010), 

http://www.bp.com/genericarticle.do?categoryId=2012968&contentId=7062487.

180 Id.

181 See Clifford Krauss and Henry Fountain, BP Funneling Some of Leaks to Surface, N.Y. TIMES (June 4, 2010); 

Interview with Richard Lynch.

182 Non-public government document.

183 Day 43: The Latest on the Oil Spill, N.Y. TIMES (June 2, 2010); The Ongoing Administration-Wide Response to 

the Deepwater BP Oil Spill (June 3, 2010), http://www.restorethegulf.gov/release/2010/06/03/ongoingadministration-wide-response-deepwater-bp-oil-spill.

184 Non-public government document.

185 Interview with Richard Lynch.

186 Non-public government document.

187 Non-public government document.

188 Non-public government document.

189 Non-public government document.

190 Letter from Doug Suttles, BP, to Admiral James Watson, FOSC (June 6, 2010).

191 Letter from Doug Suttles, BP, to Admiral James Watson, FOSC (June 21, 2010).

192 Letter from Doug Suttles, BP, to Admiral James Watson, FOSC (June 9, 2010).
Originally Released November 22, 2010

Updated January 11, 2011

- 23 -

12,

193 and collected hydrocarbons through the first freestanding riser for two days before BP shut 

in the well on July 15. BP never used the second freestanding riser system, which became 

unnecessary when the well was capped.

194

 

ii. Collection with Flow Rate as a Moving Target

The underestimates of flow rate that persisted through much of this period may have 

affected the urgency with which BP pursued additional collection capacity. BP, on occasion, 

was overly optimistic about the percentage of the oil it could collect with existing equipment. 

On June 1, Suttles of BP was quoted as saying that he expected the top hat, when connected to 

the Discoverer Enterprise with its 15,000 bbls/day capacity, to be able to collect the “vast 

majority of the oil.”195 Within days, it became apparent that the top hat and Discoverer 

Enterprise were inadequate.196 BP made the same mistake with the Q4000: On June 6, BP’s 

Hayward told the BBC that, with the Q4000 in place, “we would very much hope to be 

containing the vast majority of the oil.”197 When the Q4000 came online in mid-June, the 25,000 

bbls/day joint collection capacity between it and the Discoverer Enterprise remained insufficient. 

Suttles has since stated that he was surprised when BP’s 25,000 bbls/day capacity was not 

enough to collect all the oil.198

Nonetheless, it is unclear whether BP could have increased its collection capacity more 

rapidly than it did. Lynch of BP told Commission staff that the speed at which BP brought 

collection capacity online was limited solely by the availability of dynamically positioned 

production vessels.199 One high-level Coast Guard official challenged BP’s definition of 

availability: He told Commission staff that, prior to being pushed by the government, BP did not 

consider options such as procuring ships on charter with other companies.200 Had BP obtained 

another production vessel sooner, it might have been able to collect oil through the BOP’s kill 

line at a rate comparable to the collection rate of the Q4000.

201

 At the very least, it seems fair to 

conclude that through the beginning of June, BP did not expect that 25,000 bbls/day of collection 

capacity would be inadequate. If additional production vessels had in fact been available, BP 

could have prepared itself for that contingency.

 

193 BP Press Release, Capping Stack Installed on MC252 Well (July 12, 2010), 

http://www.bp.com/genericarticle.do?categoryId=2012968&contentId=7063637.

194 BP pursued at least one additional long term containment option that involved routing hydrocarbons from the 

Macondo well through subsea pipelines to either an abandoned well or existing pipelines nearby. Like the second 

freestanding riser, this containment option was never operationalized. Interview with Richard Lynch. 

195 Helene Cooper and Peter Baker, U.S. Opens Criminal Inquiry into Oil Spill, N.Y. TIMES (June 1, 2010).

196 See Clifford Krauss and John M. Broder, Coast Guard Sees Cleanup of Spill Lasting Until the Fall, N.Y. TIMES

(June 6, 2010).

197 BP Captures ‘10,000 Barrels’ a Day in U.S. Gulf, BBC NEWS (June 6, 2010), 

http://www.bbc.co.uk/news/10248409.

198 Interview with Doug Suttles.

199 Interview with Richard Lynch. Dynamically positioned vessels have computer controlled systems that maintain 

the vessel’s exact position and heading, despite external factors such as wind, waves, and current.

200 Interview with Coast Guard official.

201 See Letter from Doug Suttles, BP to Admiral James Watson, FOSC (June 9, 2010) (suggesting that with the 

Clear Leader attached to the kill line, BP could collect 5-10,000 bbls/day).
Originally Released November 22, 2010

Updated January 11, 2011

- 24 -

IV. The Science Team’s Evolving Role, the Capping Stack, and Killing the 

Macondo Well

While the basic pieces of the federal oversight structure were in place by mid-May, the 

oversight process continued to mature throughout June.202 By mid-June, the roles of different 

teams were better defined. MMS and the Coast Guard continued to focus on identifying hazards 

in BP’s operational procedures; national labs and U.S. Geological Survey personnel provided

information and analysis to the science advisors and, upon request, BP; and the science advisors 

conducted their own independent analyses, gave “homework” to national labs personnel, and 

helped inform the government’s ultimate decision-makers, including Secretary Chu, Secretary 

Salazar, Dr. McNutt, Dr. Hunter, Carol Browner, Director of the White House Office of Energy 

and Climate Change Policy, and Admiral Allen.203

Following the failure of the top kill, BP began presenting its source control plans for 

review by Secretary Chu’s science advisors as well as the on-site scientists from the national labs 

and U.S. Geological Survey. The on-site scientists would then prepare their own analyses of 

BP’s plans. Based upon those analyses, the science advisors would force BP to evaluate worstcase scenarios and plan for contingencies.204

 In essence, they played “devil’s advocate,” 

questioning BP’s proposals to ensure that BP had fully considered and mitigated even lowprobability risks.205

 

The government team saw this questioning of BP’s assumptions and risk management as 

essential. According to one senior government official, before the increased supervision, BP

“hoped for the best, planned for the best, expected the best.”206 One of the science advisors told 

Commission staff that, before the science team stepped up its oversight, BP had failed to 

consistently consider worst-case scenarios.207 Tooms of BP, on the other hand, expressed 

frustration to Commission staff about the nature of the science team’s pushback, arguing that 

theoretical scientists consider risk differently than engineers, that BP had expertise in managing 

risk, and that the science team slowed the containment effort.208 The government team, however, 

was skeptical of BP’s risk management practices, given that BP’s well had just blown out.209

In addition to challenging BP’s containment ideas, the science advisors developed certain 

ideas of their own and asked the on-site government engineers to pursue them. Some of the 

ideas were good ones; others required the on-site personnel to expend significant effort proving 

their lack of feasibility to the off-site science advisors.210 Several members of the on-site team 

told Commission staff that, while the science advisors added substantial value in assessing BP’s 

 

202 Interview with Coast Guard official; Interview with senior administration official.

203 Interview with Coast Guard official; Interviews with government scientists; Interview with government science 

advisor.

204 Interview with senior administration official; Interview with government scientist.

205 Interviews with government scientists.

206 Interview with senior administration official.

207 Interview with government science advisor.

208 Interview with Paul Tooms.

209 Interview with government scientist; see also Interview with senior administration official.

210 Interviews with government scientists; Interviews with senior administration official.
Originally Released November 22, 2010

Updated January 11, 2011

- 25 -

proposals, they could also be a distraction, forcing the on-site team to chase down ideas it found 

unhelpful and undermining its working relationship with BP engineers.

211

One example cited by multiple members of the national labs team involved the science 

advisors’ interest in obtaining pressure readings from the top hat.212 Because the top hat was a 

loose-fitting device, some members of the national labs team felt the data would not be 

especially useful.213 In addition, according to an MMS official, inserting a pressure gauge could 

have hindered collection by blocking a back-up port for injecting methanol into the top hat.214 

At the direction of the science team, BP installed an analog pressure gauge that had to be read 

visually by a remotely operated vehicle. When this gauge failed, BP installed a second pressure 

gauge that was physically tethered to a remotely operated vehicle that reported its readings.215 

The vehicle took readings for several days, until lightning hit the Discoverer Enterprise on June 

15, shutting down the ship’s collection capacity for over an hour. After the lightning strike, the 

gauge recorded only a slight pressure change, even though the pressure in the top hat should 

have increased significantly due to lack of collection from the ship above.216 The gauge was 

probably malfunctioning and, in retrospect, attempting to obtain data from it may not have been 

the best use of scarce resources (including the remotely operated vehicle that had to stay tethered 

to the gauge).217 As one high-ranking government official summed up the effort: Three national

labs had teams of scientists trying to make sense of a gauge that was likely clogged with hydrates 

and frozen in one position, reading nothing.

218

Another significant change to the oversight structure occurred in mid-to-late June, when 

the government team began to seek more frequent advice from BP’s industry competitors.219 

The government often sought this input through conference calls of 30 or more people, 

sometimes with BP’s participation and sometimes without.220 One senior government official 

noted that BP viewed its competitors as suffering from a conflict of interest and that at least 

some government officials agreed, taking the competitors’ advice “with a grain of salt.”221 An 

industry participant recalled that the calls were fairly disorganized, with no pre-set agenda and 

people talking over one another.222 He mentioned one instance when he was chagrined to learn 

he had been talking to Secretary Chu without realizing it.223 This individual also explained that 

industry personnel were concerned about the legal ramifications of their participation, and may 

have been cautious in giving their opinions as a result.224 Finally, he noted that he rarely had 

access to non-public data, which may have hindered his ability to offer informed opinions.

225

 

 

211 Interviews with government scientists.

212 Interviews with government scientists.

213 Interview with government scientist.

214 Interview with MMS official.

215 Interview with government scientist.

216 Id.; Interview with senior administration official.

217 Interview with government scientist.

218 Interview with senior administration official.

219 Interview with government scientist; Interview with industry executive.

220 Interview with government scientist; Interview with government science advisor; Interview with industry expert.

221 Interview with senior administration official.

222 Interview with industry expert.

223 Id.

224 Id.

225 Id.
Originally Released November 22, 2010

Updated January 11, 2011

- 26 -

Although government personnel told Commission staff that they found the industry input

helpful,

226 both the science advisors and industry participants thought that the government could 

make more effective use of industry expertise in the future by addressing some of these concerns 

in advance.

227

The extent of oversight by the science advisors continued to increase throughout June. 

On June 18, Secretary Chu sent an email to the advisory team, as well as some national labs 

scientists, describing their expanded role.228 The next day, Admiral Watson, who had replaced 

Admiral Landry as the Federal On-Scene Coordinator, issued a letter to BP formalizing the more 

extensive government review process that had begun after the failed top kill.229 Going forward, 

before BP took any action relating to containment, it had to “submit the pending decision”—

including conceptual drawings and descriptions of the capabilities and limitations of any 

equipment and procedures—to the government “for review.”230

The greater role of the government science teams came as the source control effort 

approached a critical phase. BP was well on its way toward installing a “capping stack” that 

could seal tightly over the top of the Deepwater Horizon’s BOP stack. Once installed, the 

capping stack would allow BP to shut the well in completely.

A. The Capping Stack

i. Development, Analysis, and Installation

The capping stack was essentially a smaller version of a BOP.

231

 Designed to connect to 

the top of the Deepwater Horizon’s BOP stack, it contained three rams capable of shutting off 

the flow of hydrocarbons as well as its own choke and kill lines. The idea to install a capping 

stack was not new. Both Suttles and Tooms of BP told Commission staff that BP internally 

discussed the idea of a cap with a tight-fitting seal within a week of the blowout.232 As noted 

above, BP and the government had shelved the idea of shutting in the well following the top kill, 

in part because of well integrity concerns relating to the rupture disks in the 16” casing. The 

government and BP had to consider those concerns when planning for use of the capping stack. 

 

226 Interview with government science advisor; Interview with senior administration official.

227 Interview with industry expert; Non-public government science advisor email.

228 Interview with government science advisor.

229 Letter from Admiral James Watson, FOSC, to Doug Suttles, BP (June 19, 2010).

230 Id.

231 Interview with senior administration official.

232 Interview with Doug Suttles; Interview with Paul Tooms.
Originally Released November 22, 2010

Updated January 11, 2011

- 27 -

BP’s planning for the capping stack operation began in earnest in mid-June, with the 

national labs providing guidance.233 One key analysis, performed by BP with national labs 

support, concluded that the capping stack was not too heavy to be placed on the BOP stack, even 

though the latter was listing at two degrees from vertical.234 The government also pushed BP to 

install two pressure sensors in the capping stack.

235

 These sensors were accurate to plus or 

minus two psi; by contrast, the original BOP stack had only one pressure sensor, which was 

accurate to plus or minus 400 psi.236 The accurate sensors in the capping stack later proved 

critical in generating wellhead pressure readings and a flow-rate estimate.

At the end of June or in early July, Dr. Hunter from the science team and James Dupree 

of BP traveled to Washington, D.C. to brief a group of high-ranking government officials, which 

included Secretaries Chu and Salazar, Secretary of Homeland Security Janet Napolitano, EPA 

Administrator Lisa Jackson, Browner, and Dr. Jane Lubchenco, Administrator of the National 

Oceanic and Atmospheric Administration.237 The briefing presented the capping stack as the 

preferred course forward, and the high-ranking officials gave their approval.238 The next day, 

Secretary Chu and Dr. Hunter briefed the President, who gave his approval as well.239

It appears that the government delayed installation of the capping stack for a few days to 

continue analyzing the significant risks associated with shutting in the well.

240

 One key analysis 

was of the geology surrounding the Macondo well. Because the condition of the well was 

unknown, this analysis assumed the rupture disks in the 16” casing had collapsed and examined 

whether, if the well were shut in, hydrocarbons that escaped sideways into the rock formation 

would travel up into the ocean. The government’s Well Integrity Team, led by scientists from 

the national labs and the U.S. Geological Survey and supported by experts from industry, 

academia, and MMS, presented their findings on this question in a July 12 report.241 The Team 

analyzed the geologic conditions near the most likely point of escape, and concluded that it 

would take a total of approximately 100,000 barrels flowing through the rupture disks for oil to 

create one or more paths up to the sea floor.242 After initially preferring a more optimistic 

estimate—i.e., believing that a larger volume of escaping oil was necessary for oil to reach the 

sea floor243—BP appears to have accepted this analysis.244 

The Well Integrity Team next examined whether—assuming that shutting in the well 

caused oil to flow through the rupture disks, into the formation, and up to the sea floor—the flow 

paths up to the sea floor would close or “heal” if BP reopened the capping stack. The Team’s 

conclusion, supported by a consensus of industry representatives who considered the question on 

 

233 Interview with government science advisor; Interview with Richard Lynch.

234 Non-public government document.

235 Non-public government document; Interview with government science advisor.

236 Interview with government science advisor.

237 Interview with government science advisor.

238 Id.

239 Id.

240 BP, ANSWERS TO FOLLOW-UP QUESTIONS POSED BY PRESIDENTIAL COMMISSION STAFF; Interview with Richard 

Lynch; Interview with Paul Tooms; Non-public government document.

241 Non-public government document.

242 Id.; Interview with government scientist; Non-public government science advisor notes.

243 Interview with senior administration official.

244 Non-public BP document.
Originally Released November 22, 2010

Updated January 11, 2011

- 28 -

a conference call, was that the path would heal if BP reopened the capping stack with sufficient 

speed.245 Industry participants and the Well Integrity Team were most concerned that flow paths 

between the well’s steel casings and the surrounding rock would develop and remain open, 

resulting in an uncontrolled flow of oil to the sea floor.

246

 The Team’s final step was to consider 

what monitoring protocol would detect possible leaks into the rock formation in time to reopen 

the stack and to avoid creating a permanent flow path to the sea floor. The Team settled on a 

multi-tiered approach that involved visual, seismic, and sonar monitoring from ships and 

remotely operated vehicles, acoustic monitoring from a sensor at the wellhead, and wellhead 

pressure monitoring from gauges in the capping stack—all aimed at determining whether the 

well’s integrity had been compromised and oil was flowing sideways into the rock.247 

A second set of concerns related to closing the capping stack involved the risk that 

capping would increase the pressure inside the well and burst either the rupture disks (if they had 

not already collapsed) or the outermost casings between the top of the 16” casing and the 

wellhead.248 BP and the government were worried that capping could cause pressure at the

wellhead to reach 8,900 psi,

249 and pressures farther down the well to reach levels high enough to 

cause new ruptures.250 One industry executive recalled discussing this issue on a conference call 

with the science advisors. On the call, he expressed concern with allowing pressure at the 

wellhead to climb above the pressures recorded during the top kill (about 6,300 psi).251 In his 

view, that would be traveling in uncharted territory, with uncertain risks.252

In early July, as analysis of these concerns continued, BP prepared to install the capping 

stack. In a July 8 letter, Admiral Allen told BP that, going forward, it would need his approval 

before taking action on key “decision points.”253 The next day, he authorized BP to proceed with 

installation, but not to close the stack.254 The operation began on July 10 and was extremely 

complicated. After removing the top hat from the top of the riser, remotely operated vehicles 

had to unbolt the stub of riser connected to the top of the BOP stack, remove this stub, assess 

whether pieces of drill pipe were sticking up through the top of the BOP stack, slide the capping 

stack into place, and bolt the capping stack to the top of the BOP stack. BP’s Lynch told 

Commission staff that the installation team had closely examined each individual bolt that had to 

be removed with a subsea hydraulic wrench and determined the appropriate tool shape and 

torque to be applied.255 BP had run through the entire operation on land. It had also practiced 

using remotely operated vehicles to remove bolts on the piece of riser lying on the seabed, which 

it had previously cut from the top of the BOP stack.256 The capping stack was installed without 

 

245 Interview with government scientist; Interview with industry expert.

246 Interview with senior administration official.

247 Interview with government scientist.

248 Interview with government science advisor.

249 Id.; Non-public government document.

250 Interview with government science advisor.

251 Interview with industry expert; Non-public BP document.

252 Interview with industry expert.

253 Letter from Admiral Thad Allen, NIC, to Bob Dudley, BP (July 8, 2010). This appears to be the first directive 

issued by Admiral Allen to BP regarding its well control plans. From this point on, his personal authorization was 

necessary before major operations could commence.

254 Letter from Admiral Thad Allen, NIC, to Bob Dudley, BP (July 9, 2010); Non-public government document.

255 Interview with Richard Lynch.

256 Interview with Richard Lynch; Interview with Doug Suttles.
Originally Released November 22, 2010

Updated January 11, 2011

- 29 -

incident by July 12.257 Suttles described the installation process as the best source control 

operation of the entire containment effort.258

ii. Shut-In

After installation, BP prepared to temporarily shut the capping stack in a planned “well 

integrity test” to determine whether the well had been compromised and oil could flow sideways 

into the formation. Admiral Allen explained the need for the test in a public statement: “The 

measurements that will be taken during this test will provide valuable information about the 

condition of the well below the sea level and help determine whether or not it is possible to shut 

the well for a period of time, such as during a hurricane or bad weather, between now and when 

the relief wells are complete.”259 The test was to last anywhere from 6 to 48 hours, depending on 

the measurements observed.260 In a July 12 letter, Admiral Allen formally authorized the test to 

begin.261

The well integrity test as authorized on July 12 never occurred. About two hours before 

it was to begin on July 13, the government team, including the science advisors, met with BP and 

industry representatives, including Exxon (in person) and Shell (over the phone).262 Secretary 

Chu and Admiral Allen were both present in person.263 According to Tooms of BP, participants 

in the meeting, especially Exxon, questioned the wisdom of the test.264 The science advisors had 

asked industry representatives to identify potential risks for the government’s consideration, and 

Exxon and Shell did so, raising new concerns about well integrity that had yet to be considered 

by BP or the government.265 Because Secretary Chu and the science advisors believed that these

risks required further consideration,266 Admiral Allen delayed the well integrity test to allow for 

24 hours of additional analysis.267

 

257 Statement from National Incident Commander Admiral Thad Allen on Well Integrity Test (July 12, 2010), 

http://www.restorethegulf.gov/release/2010/07/12/statement-national-incident-commander-admiral-thad-allen-wellintegrity-test.

258 Interview with Doug Suttles.

259 Statement from National Incident Commander Admiral Thad Allen on Well Integrity Test (July 12, 2010).

260 Id.

261 Letter from Admiral Thad Allen, NIC, to Bob Dudley, BP (July 12, 2010).

262 Interview with government scientist.

263 Id.

264 Interview with Paul Tooms.

265 Interview with government scientist; Interview with government science advisor; Interview with industry 

executive.

266 Interview with government scientist.

267 Statement from National Incident Commander Admiral Thad Allen on Well Integrity Test (July 13, 2010), 

http://www.restorethegulf.gov/release/2010/07/13/statement-national-incident-commander-admiral-thad-allen-wellintegrity-test.
Originally Released November 22, 2010

Updated January 11, 2011

- 30 -

Overnight, the government science teams reached out to additional experts from industry 

and academia to evaluate the concerns that Exxon and Shell had raised.

268

 By 10:00 the next 

morning, those experts had reassured the government that the risks were manageable.

269

 With 

the government teams satisfied, Admiral Allen reauthorized the well integrity test.270 Again the 

test was to last from 6 to 48 hours, and the government required BP to continuously monitor 

pressure, sonar, acoustic, and visual data as recommended by the Well Integrity Team.271

Reflecting the more rigorous oversight that followed the failed top kill, the government 

and BP developed a much more structured protocol for implementing the well integrity test than 

had existed for the top kill. Although the Well Integrity Team had calculated that it would take a 

total leak of approximately 100,000 barrels for hydrocarbons to reach the sea floor, the 

government determined that it would permit a leak of only 20,000 barrels before requiring the 

capping stack to be reopened.272 Using this figure and an estimate for the expected pressure at 

shut-in derived from BP’s modeling of the reservoir, the Well Integrity Team created guidelines 

for the test.273 If the pressure at shut-in was less than 6,000 psi, major well damage was likely: 

BP would have to terminate the test within six hours and reopen the well.274 If the shut-in 

pressure was greater than 7,500 psi, the risk of a leak was low, and the test could proceed for the 

full 48 hours.275 Finally, if the shut-in pressure was between 6,000 and 7,500 psi, the risk of a 

leak was uncertain—either there was a medium-sized leak into the formation or the reservoir was 

highly depleted.276 Under this scenario, the test could proceed for 24 hours.277 These guidelines 

were condensed into a simple graphic, reproduced as Figure 4. As noted above, if the pressure 

was very high, there was also the risk of causing a new rupture.

 

268 Interview with senior administration official.

269 Id.

270 Letter from Admiral Thad Allen, NIC, to Bob Dudley, BP (July 14, 2010).

271 Id.; Interview with government scientist; Interview with senior administration official.

272 Interview with government scientist; Interview with senior administration official; Non-public government 

document.

273 Non-public government document; Interview with government scientist.

274 Non-public government document.

275 Id.

276 Id.

277 Id.
Originally Released November 22, 2010

Updated January 11, 2011

- 31 -

Figure 4

278

After a 24-hour delay to repair a minor leak discovered in the capping stack, BP shut the 

stack and began the well integrity test at 2:25pm on July 15.279 For the first time in 87 days, no 

oil flowed into the Gulf of Mexico. Initial wellhead pressure readings were just over 6,600 psi, 

squarely in the uncertain middle range, and rising slowly.280 Later that afternoon, the science 

advisors, including Dr. McNutt and Dr. Hunter, met with Secretaries Salazar and Chu to consider 

the pressure data and whether to keep the well shut in. A member of the Well Integrity Team 

reported that, according to his original model, the shut-in pressure indicated an oil leak into the 

formation of about 3,500 bbls/day.281 From there, discussion within the group appears to have 

turned firmly against keeping the well closed. Dr. Garwin, who had opposed even undertaking 

the well integrity test,282 voiced the strongest opinion to that effect.283 He argued that BP ought 

to stop the test immediately and wondered whether it was already too late.284 Several 

participants were concerned that the monitoring systems might be unable to detect leakage.285 

No one at the meeting appears to have argued in favor of keeping the well shut in.286 After an 

hour and a half, a consensus among the science advisors had developed: Oil was leaking into the 

 

278 Derived from Non-public BP document.

279 Campbell Robertson and Henry Fountain, BP Says Oil Flow Has Stopped as Cap Is Tested, N.Y. TIMES (July 15, 

2010).

280 Non-public government document; Non-public government science advisor notes.

281 Non-public government science advisor notes.

282 Interview with government scientist; Interview with MMS official; Interview with government science advisor. 

Dr. Garwin advocated continued surface collection as well as the immediate development of a subsea collection 

system, with oil-gas separation and storage capacity, for use if a hurricane required the evacuation of surface 

vessels.

283 Non-public government science advisor notes; Interview with government science advisor. 

284 Non-public government science advisor notes.

285 Id.

286 Id.
Originally Released November 22, 2010

Updated January 11, 2011

- 32 -

formation, and the Coast Guard should order BP to reopen the capping stack and resume 

collecting oil from the well.287

BP evidently learned of this emerging consensus within the government to reopen the 

capping stack, and became concerned. Suttles called MMS Regional Director Lars Herbst to ask 

for his view of the well integrity test.288 Herbst, who had not participated in the meeting with the 

science advisors, examined the pressure data and agreed with BP that the well should stay closed 

overnight.289 BP apparently relied in part on Herbst’s support in making its case to the 

government that the well should remain shut in.290

Following meeting with the science advisors, Admirals Allen and Cook, Browner, 

Secretaries Chu and Salazar, Dr. McNutt, and perhaps others had a series of conversations to 

determine how to proceed.291 The stakes were high. Keeping the stack shut could cause an 

underground blowout and, in the worst case, loss of a significant portion of the 110 million barrel 

reservoir into the Gulf.

292 That risk had to be balanced against the need to stop the spill, an 

ongoing environmental disaster.293 Participants in the conversations were aware of the 

importance and public impact of their decision: The public wanted the well shut in and the flow 

of oil into the Gulf stopped, but the risk of causing greater harm was real.294 

According to interviews conducted by Commission staff, Admiral Cook made the

argument that eventually prevailed. He reminded the others that, before the test began, BP and 

the government had considered the possibility of pressure measurements like those being 

observed. Both parties had agreed that, in such a case, the test should last 24 hours, with 

consultation between the parties prior to reopening the well.

295

 One participant recalled general 

agreement that, while the data supported reopening the capping stack, under the guidelines 

established prior to shut-in, the stack could stay closed during the night.296

This additional time proved critical. Steve Hickman of the U.S. Geological Survey was 

in BP’s Houston headquarters as pressure data started coming in during the afternoon and 

evening of July 15. Using the camera on his cellular phone, he took a picture of the initial 

“pressure curve,” or plot of pressure readings during the shut in, and sent it to Paul Hsieh, 

another U.S. Geological Survey member of the Well Integrity Team who was then in Menlo 

Park, California.297 BP had earlier sent an email to government and BP personnel indicating that 

the results of the well integrity test were “market sensitive,” and warning against sharing data 

due to concerns about insider trading.

298

 Although the email indicated that information about 

 

287 Id.

288 Interviews with government officials.

289 Interview with government official.

290 Id.

291 Interview with senior administration official; Non-public government science advisor notes.

292 Interviews with government scientists.

293 Interviews with government scientists.

294 Interview with government scientist.

295 Interview with Coast Guard official; Interview with senior administration official.

296 Interview with government science advisor.

297 Interview with senior administration official; Interview with government scientist.

298 Non-public BP email.
Originally Released November 22, 2010

Updated January 11, 2011

- 33 -

how the test was progressing could be communicated to others if it was “strictly necessary for 

the procedure,”299 Hsieh apparently relied on the data in the single cellular phone picture to 

model the reservoir.300

Overnight, Hsieh attempted to develop a model that explained the results of the well 

integrity test. The biggest question was why the pressure had climbed above 6,600 psi but not to 

the minimum expected shut-in pressure of 7,500 psi.301 The answer was that the expectation had 

been based on an incomplete understanding of the reservoir’s geometry and on pressure readings 

from a gauge at the bottom of the BOP, which was inaccurate and functioning only 

sporadically.302 Using accurate pressure readings from the capping stack, along with a flow-rate 

estimate of 55,000 bbls/day and BP’s estimate that the reservoir originally contained 110 million 

barrels of oil, Hsieh was able to generate a model of the depleted reservoir that predicted the 

observed shut-in pressures without having to assume a significant leak into the formation.303

The next morning, the government principals and the science advisors—who had been 

convinced the night before that opening up the stack was necessary—hosted a meeting. BP 

presented its explanation of why pressures had built to the level observed and argued, in detail, 

that the well should remain shut in.304 Hsieh also presented his model, demonstrating that there 

was a reasonable explanation for why the pressure was lower than expected.305 Participants with 

whom staff spoke had different recollections as to whether BP’s or Hsieh’s presentation carried 

more weight.

306 The outcome of the meeting, however, was clear. The stack would stay shut, 

with government reevaluation of that decision every six hours.

Unrealized at the time, a critical point had passed: BP would not have to reopen the 

stack, and oil had finally stopped leaking from the Macondo well into the Gulf. Intense 

monitoring of the area around the wellhead continued and, on July 17, increased.307 That day, 

the government brought in a sonar ship from the National Oceanic and Atmospheric 

Administration and doubled the number of seismic mapping runs over the site.308 As more time 

passed, Hsieh was able to improve his model using seismic data. The model continued to predict 

the behavior of the well, and a leak into the formation became a less and less likely scenario.309 

Although the well integrity test had originally been scheduled to last a maximum of 48 hours, 

Admiral Allen began to extend it in 24-hour increments beginning on July 17.310 With each 

 

299 Id.

300 Interview with government scientist; Interview with senior administration official.

301 Interview with government scientist.

302 Interview with government scientist; Interview with government science advisor.

303 Interview with government scientist; Interview with senior administration official; Non-public government 

document.

304 Interview with Paul Tooms.

305 Interview with government scientist; Interview with senior administration official.

306 Interviews with government science advisors; Interview with senior administration official.

307 Statement by National Incident Commander Admiral Thad Allen on Well Integrity Test (July 17, 2010), 

http://www.restorethegulf.gov/release/2010/07/17/statement-national-incident-commander-admiral-thad-allen-wellintegrity-test.

308 Id.

309 Interview with government scientist.

310 Statement by National Incident Commander Admiral Thad Allen on Well Integrity Test (July 17, 2010).
Originally Released November 22, 2010

Updated January 11, 2011

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passing day, the government grew more certain of the well’s integrity.311 On July 24, in his daily 

press briefing, Admiral Allen stated that “our confidence [in the capping stack] is increasing and 

we have better integrity in the well than we may have guessed.” 312 

B. Killing the Well

While the capping stack remained in place, with pressure inside it continuing to build, BP 

raised the possibility of killing the well before the relief wells were completed through a 

procedure called a “static kill” or “bullhead kill.” Like the top kill, the static kill involved 

pumping heavy drilling mud into the well in an effort to push hydrocarbons back into the 

reservoir. Because the hydrocarbons were already static, however, the necessary pumping rates 

for the static kill to succeed were far lower than for the top kill. BP first publicly mentioned use 

of a static kill on July 19, in a letter from Bob Dudley, then heading BP’s response in the Gulf, to 

Admiral Allen.313 In a presentation dated July 21, BP made the case for the static kill to 

government scientists.314 If successful, the kill would reduce or eliminate the pressure within the 

capping stack and hydrostatically contain the well during hurricane season.

315

BP could not, however, immediately move forward with the static kill. The government 

and BP appear to have agreed that, before the static kill could begin, BP should finish running 

and cementing a casing in the first relief well, which was then only a few lateral feet from the 

Macondo well.316 This avoided leaving an open well and potential flow path near a part of the 

 

311 Interview with government science advisor. There were, however, at least two occasions when reopening the 

capping stack was a possibility. On July 18, a seep of methane was discovered some distance from the well; by the 

next day, however, it became clear that the seep was natural and not a leak from Macondo well. Letter from 

Admiral Thad Allen, NIC, to Bob Dudley, BP (July 18, 2010); Statement by National Incident Commander Admiral 

Thad Allen (July 19, 2010), http://www.restorethegulf.gov/release/2010/07/19/statement-national-incidentcommander-admiral-thad-allen; Henry Fountain, BP Considers New Plan To Permanently Seal Well, N.Y. TIMES 

(July 19, 2010). On July 22, with Tropical Storm Bonnie bearing down on the Gulf, Admiral Allen, on the advice of 

Secretary Chu, decided to keep the well shut in while some of the ships monitoring the capping stack and well had 

to evacuate. Statement by National Incident Commander Admiral Thad Allen on Tropical Storm Bonnie (July 22, 

2010), http://www.restorethegulf.gov/release/2010/07/22/statement-national-incident-commander-admiral-thadallen-tropical-storm-bonnie; Henry Fountain, Storm Threat Forces Ships To Leave Oil Spill Site, N.Y. TIMES (July 

22, 2010).

312 Press Briefing by National Incident Commander Admiral Thad Allen and NOAA Administrator Dr. Jane 

Lubchenco (July 24, 2010), http://www.restorethegulf.gov/release/2010/07/24/transcript-press-briefing-nationalincident-commander-admiral-thad-allen-and-noaa.

313 Letter from Bob Dudley, BP, to Admiral Thad Allen, NIC (July 19, 2010).

314 Non-public BP document.

315 Id.

316 Id.; Press Briefing by National Incident Commander Admiral Thad Allen (July 21, 2010), 

http://www.restorethegulf.gov/release/2010/07/21/transcript-pressbrief-national-incident-commander-admiral-thadallen-july-21-2010.
Originally Released November 22, 2010

Updated January 11, 2011

- 35 -

Macondo well where there had been well integrity concerns.317 With Tropical Storm Bonnie 

approaching, the Development Driller III, which was drilling the first relief well, had to leave the 

drill site before its crew could run and cement the casing.318 Although the rig was able to return 

and restart work by July 25,319 the work was delayed by debris that had accumulated in the 

well,320 and BP was not able to finish running and cementing the casing until August 2.321

Aside from the relief well, the government’s major concern with the static kill was the 

pressure it would put on the Macondo well. The science advisors discussed with industry experts

whether it was wise to increase the pressure on the well beyond what the shut-in had indicated 

the well could hold.322 On July 28, BP received an unsolicited letter from Pat Campbell, a VicePresident at Superior Energy Services, which owned BP contractor Wild Well Control, 

recommending in no uncertain terms that the static kill not proceed.323 Campbell, who had 

worked with legendary well control expert Red Adair and had been profiled in the New York 

Times prior to the top kill,324 reiterated the concerns that had been expressed to the science team 

by industry—namely, that the only pressure the well could withstand for certain was the shut-in 

pressure, approximately 6,920 psi at the time he wrote the letter.

325

 According to Tooms, 

Campbell privately assured BP that, through the letter, he was only hoping to limit his 

company’s exposure to liability if the static kill went awry.326 Commission staff have not been 

able to corroborate Tooms’s recollection of the letter through interviews with individuals outside 

BP.327

After considering Campbell’s concern, by the time the Development Driller III had 

finished cementing the casing in the relief well, the government team had approved the plan for 

the static kill.328 BP would have to abort the kill if the pressure at the wellhead exceeded 8,000 

psi, significantly less than the capping stack’s pressure rating.329 A mud injection test began on 

August 3, and pressure at the wellhead increased by only approximately 35 psi before beginning 

 

317 Press Briefing by National Incident Commander Admiral Thad Allen (July 21, 2010).

318 Press Briefing by National Incident Commander Admiral Thad Allen (July 23, 2010), 

http://www.restorethegulf.gov/release/2010/07/23/transcript-press-briefing-national-incident-commander-admiralthad-allen-july-23-.

319 Press Briefing by National Incident Commander Admiral Thad Allen (July 25, 2010), 

http://www.restorethegulf.gov/release/2010/07/25/transcript-press-briefing-national-incident-commander-admiralthad-allen.

320 Press Briefing by National Incident Commander Admiral Thad Allen (July 23, 2010), 

http://www.restorethegulf.gov/release/2010/07/30/transcript-press-briefing-national-incident-commander-admiralthad-allen.

321 Non-public government document.

322 Interview with industry expert.

323 Letter from Pat Campbell, Superior Energy Services, to Richard Lynch, BP (July 28, 2010).

324 See Henry Fountain, Expert is Confident about Sealing Oil Well, N.Y. TIMES (May 24, 2010).

325 Letter from Pat Campbell.

326 Interview with Paul Tooms.

327 Interview with well control expert.

328 Press Briefing by National Incident Commander Admiral Thad Allen (Aug. 2, 2010), 

http://www.restorethegulf.gov/release/2010/08/02/transcript-press-briefing-national-incident-commander-admiralthad-allen.

329 Id.; Non-public government document.
Originally Released November 22, 2010

Updated January 11, 2011

- 36 -

to drop.330 Based on these positive results, BP began slowly pumping more heavy drilling mud 

into the well later that day and, at 11:00pm, achieved hydrostatic control of the well.331 On the 

evening of August 4, Admiral Allen authorized BP to follow the mud with cement,332 a process 

that BP completed the next day.333 Finally, on August 8, Admiral Allen reported that BP had 

pressure-tested the cement, which was holding.334

BP proceeded to finish drilling the first relief well to finally kill the Macondo well. On 

September 19, 152 days after the April 20 blowout, Admiral Allen announced the end of the 

source control effort:

After months of extensive operations planning and execution under the direction 

and authority of the U.S. government science and engineering teams, BP has 

successfully completed the relief well by intersecting and cementing the well 

nearly 18,000 feet below the surface. With this development, which has been 

confirmed by the Department of the Interior’s Bureau of Ocean Energy 

Management, we can finally announce that the Macondo 252 well is effectively 

dead.335

V. Issues for Commission Consideration

There were many success stories in the effort to control the Macondo well, including, but 

not limited to, the ultimate successes of capping and killing it. The operation of numerous ships 

and remotely operated vehicles, in close proximity to one another and to gushing hydrocarbons,

with no significant accidents was a credit both to BP’s controls and to the Coast Guard and MMS 

officials who reviewed BP’s procedures. BP’s efforts to develop multiple source control options

simultaneously were herculean. And the speed with which government scientists, with little

background in deep-sea petroleum engineering, established meaningful oversight was truly 

impressive. The hundreds of individuals who spent the spring and summer of 2010 working to 

stop the spill, under enormous pressure and conditions of great uncertainty, have much in which 

to take pride.

These remarkable efforts were necessary, however, because of a lack of advance 

preparation by industry and government. The story of source control during the Deepwater 

Horizon spill therefore suggests the following potential findings and lessons for Commissioner 

consideration.

 

330 BP Press Release, Static Kill Injectivity Testing Commences on MC252 Well (Aug. 3, 2010), 

http://www.bp.com/genericarticle.do?categoryId=2012968&contentId=7064164; Non-public government document.

331 BP Press Release, Well Reaches Static Condition; Well Monitoring Underway (Aug. 4, 2010), 

http://www.bp.com/genericarticle.do?categoryId=2012968&contentId=7064173.

332 Statement by National Incident Commander Admiral Thad Allen (Aug. 4, 2010), 

http://www.restorethegulf.gov/release/2010/08/04/statement-national-incident-commander-admiral-thad-allen.

333 Non-public government document.

334 Face the Nation, CBS NEWS (Aug. 8, 2010), http://www.cbsnews.com/htdocs/pdf/FTN_080810.pdf.

335 Statement from Admiral Allen on the Successful Completion of the Relief Well (Sept. 19, 2010), 

http://www.restorethegulf.gov/release/2010/09/19/statement-admiral-allen-successful-completion-relief-well.
Originally Released November 22, 2010

Updated January 11, 2011

- 37 -

First, beyond attempting to close the BOP stack and drilling a relief well, at the time of 

the blowout on April 20, there were no proven options for source control in deepwater. 

Although BP was able to develop new source control technologies in a compressed timeframe, 

the containment effort would have benefited from prior research and development, preparation, 

and contingency planning. The Deepwater Horizon experience suggests that deepwater 

operators should be required to create detailed source control plans that demonstrate their ability 

to respond to blowouts. The Commission may wish to recommend subjecting those source 

control plans to review by agencies with relevant expertise as well as outside experts.

Second, at the time of the blowout, the government was unprepared to oversee a 

deepwater source control effort. After the spill began, the public expected such oversight, but 

neither MMS nor the Coast Guard had the expertise to supervise BP’s decisions. An effective 

oversight structure was not in place until late May. The delay may have contributed to a public 

impression that BP was running the source control effort. This experience suggests that, to 

provide meaningful supervision, the government needs access to sufficient expertise in 

deepwater drilling and containment—through the Department of the Interior, the national labs, 

outside scientists, or otherwise. Thus, the Commission may wish to recommend that the 

government develop and maintain additional in-house expertise in petroleum engineering, as 

well as formalize procedures to make the best use of outside industry experts during an 

incident.336

Third, underestimates of the flow rate appear to have impeded planning for sourcecontrol efforts like the cofferdam and, especially, the top kill. These underestimates may also 

have led BP to misinterpret the top kill’s failure as evidence of a well integrity problem. Dr. 

McNutt recently stated that, if a similar blowout occurs in the future, the government will be able 

to quickly and reliably estimate the flow rate using the oceanographic techniques that eventually 

provided an accurate estimate of the flow from the Macondo well.337 This suggests that the 

government and responsible party should prioritize accurate estimation of flow rate early in a 

well control effort. 

Fourth, the lack of reliable diagnostic tools—such as accurate pressure gauges at the 

wellhead and a means of understanding the position of the BOP’s rams—complicated the 

containment effort. The government and BP expended significant resources on attempts to 

collect data, like gamma-ray imaging of the BOP stack and inserting pressure sensors in the top 

hat. The lack of reliable data suggests that the government should require industry to equip BOP 

stacks with diagnostic tools that would provide more information in the case of a blowout.

 

336 On November 2, 2010, Secretary Salazar proposed to establish an Ocean Energy Safety Institute, to be housed at 

the Department of the Interior. Through partnerships across government agencies, with industry, and with the 

scientific and academic communities, the Institute intends, among other things, to develop “an expertise base useful 

both for preventing and responding to accidents,” as well as “a larger cadre of technical experts who can oversee or 

otherwise participate in deepwater drilling-related activities.” Department of the Interior Press Release, Salazar 

Proposes Ocean Energy Safety Institute (Nov. 2, 2010). Because this proposal is at an early stage, it is as yet 

unclear to Commission staff whether the Institute will be a source of the government expertise needed to oversee a 

deepwater source control effort and a vehicle to access industry expertise during such an effort.

337 Transcript, Deepwater Blowout Containment Conference (Sept. 22, 2010), 

http://www.doi.gov/news/video/Deepwater-Blowout-Containment-Conference.cfm.
Originally Released November 22, 2010

Updated January 11, 2011

- 38 -

Fifth, in designing the Macondo well, BP does not appear to have considered how its use 

of rupture disks would impact the integrity of the well during a post-blowout source control 

effort.338 Concerns about integrity—focused primarily, but not entirely, on the rupture disks—

significantly complicated the process of controlling the Macondo well. By highlighting the 

problem of the rupture disks, Commission staff do not intend to suggest that use of such disks is 

inappropriate. Staff have been told that rupture disks may play an important role in relieving 

annular pressure under certain circumstances.339 The Deepwater Horizon experience, however, 

raises a larger concern. As one BP well control contractor told Commission staff, it is not 

standard industry practice to consider, at the well design phase, what would happen if an 

operator were to lose control of the well.340 The drawn-out effort to control the Macondo well 

suggests that this practice should change: Operators and government regulators should consider 

the potential need for post-blowout source control at the well design stage.

Sixth and finally, because BP is one of the world’s largest companies, it had the resources 

to bankroll and implement a massive containment effort—and still needed 87 days to stop the 

flow of oil into the Gulf. All deepwater operators do not have BP’s resources. The Commission 

may wish to consider recommendations aimed at requiring smaller deepwater operators to 

demonstrate the capacity to respond to a disaster of this magnitude, whether through bonding or 

insurance, membership in industry consortia focused on well control, or otherwise.

 

338 Interview with Doug Suttles.

339 Interview with Paul Tooms.

340 Interview with well control expert.