Deepwater Horizon explosion
Encyclopedia
The Deepwater Horizon drilling rig explosion refers to the April 20, 2010 explosion and subsequent fire on the Deepwater Horizon
Deepwater Horizon
Deepwater Horizon was an ultra-deepwater, dynamically positioned, semi-submersible offshore oil drilling rig owned by Transocean. Built in 2001 in South Korea by Hyundai Heavy Industries, the rig was commissioned by R&B Falcon, which later became part of Transocean, registered in Majuro, Marshall...

 semi-submersible Mobile Offshore Drilling Unit (MODU), which was owned and operated by Transocean
Transocean
Transocean Ltd. is one of the world's largest offshore drilling contractors. The company rents floating mobile drill rigs, along with the equipment and personnel for operations, to oil and gas companies at an average daily rate of US$282,700...

 and drilling for BP
BP
BP p.l.c. is a global oil and gas company headquartered in London, United Kingdom. It is the third-largest energy company and fourth-largest company in the world measured by revenues and one of the six oil and gas "supermajors"...

 in the Macondo Prospect
Macondo Prospect
The Macondo Prospect is an oil and gas prospect in the United States Exclusive Economic Zone of the Gulf of Mexico, off the coast of Louisiana...

 oil field
Oil field
An oil field is a region with an abundance of oil wells extracting petroleum from below ground. Because the oil reservoirs typically extend over a large area, possibly several hundred kilometres across, full exploitation entails multiple wells scattered across the area...

 about 40 miles (64.4 km) southeast of the Louisiana
Louisiana
Louisiana is a state located in the southern region of the United States of America. Its capital is Baton Rouge and largest city is New Orleans. Louisiana is the only state in the U.S. with political subdivisions termed parishes, which are local governments equivalent to counties...

 coast. The explosion killed 11 workers and injured 16 others; another 99 people survived without serious physical injury. It caused the Deepwater Horizon to burn and sink, and started a massive offshore oil spill
Deepwater Horizon oil spill
The Deepwater Horizon oil spill is an oil spill in the Gulf of Mexico which flowed unabated for three months in 2010, and continues to leak fresh oil. It is the largest accidental marine oil spill in the history of the petroleum industry...

 in the Gulf of Mexico
Gulf of Mexico
The Gulf of Mexico is a partially landlocked ocean basin largely surrounded by the North American continent and the island of Cuba. It is bounded on the northeast, north and northwest by the Gulf Coast of the United States, on the southwest and south by Mexico, and on the southeast by Cuba. In...

; this environmental disaster is now considered the second largest in U.S. history, behind the Dust Bowl
Dust Bowl
The Dust Bowl, or the Dirty Thirties, was a period of severe dust storms causing major ecological and agricultural damage to American and Canadian prairie lands from 1930 to 1936...

.

Deepwater Horizon

The Deepwater Horizon was a floating semi-submersible drilling unit — a fifth-generation, ultra-deepwater, dynamically positioned
Dynamic positioning
Dynamic positioning is a computer controlled system to automatically maintain a vessel's position and heading by using its own propellers and thrusters...

, column-stabilized drilling rig owned by Transocean
Transocean
Transocean Ltd. is one of the world's largest offshore drilling contractors. The company rents floating mobile drill rigs, along with the equipment and personnel for operations, to oil and gas companies at an average daily rate of US$282,700...

 and built in Korea
Korea
Korea ) is an East Asian geographic region that is currently divided into two separate sovereign states — North Korea and South Korea. Located on the Korean Peninsula, Korea is bordered by the People's Republic of China to the northwest, Russia to the northeast, and is separated from Japan to the...

. The platform was 396 feet (121 m) long and 256 feet (78 m) wide and could operate in waters up to 8000 feet (2,438.4 m) deep, to a maximum drill depth of 30000 feet (9,144 m). Press releases from Transocean
Transocean
Transocean Ltd. is one of the world's largest offshore drilling contractors. The company rents floating mobile drill rigs, along with the equipment and personnel for operations, to oil and gas companies at an average daily rate of US$282,700...

 state the platform had historically been used for deeper wells, including the deepest underwater gas and oil well in history at 35055 feet (10,684.8 m) in 2009. The platform was built by Hyundai Heavy Industries
Hyundai Heavy Industries
Hyundai Heavy Industries Co., Ltd. is the world's largest shipbuilding company, headquartered in Ulsan, South Korea. The company is a subsidiary of Hyundai Heavy Industries Group...

 in South Korea and completed in 2001. It was owned by Transocean, operated under the Marshalese
Marshall Islands
The Republic of the Marshall Islands , , is a Micronesian nation of atolls and islands in the middle of the Pacific Ocean, just west of the International Date Line and just north of the Equator. As of July 2011 the population was 67,182...

 flag of convenience
Flag of convenience
The term flag of convenience describes the business practice of registering a merchant ship in a sovereign state different from that of the ship's owners, and flying that state's civil ensign on the ship. Ships are registered under flags of convenience to reduce operating costs or avoid the...

, and was under lease to BP
BP
BP p.l.c. is a global oil and gas company headquartered in London, United Kingdom. It is the third-largest energy company and fourth-largest company in the world measured by revenues and one of the six oil and gas "supermajors"...

 until September 2013. At the time of the explosion, the Deepwater Horizon was on Mississippi Canyon
Mississippi Canyon
The Mississippi Canyon is an undersea canyon in the Central Gulf of Mexico, south of Louisiana. According to the U.S. Geological Survey GLORIA Mapping Program, it is the dominant feature of the north-central Gulf of Mexico. According to GCAGS Transactions, it has an average width of , and a length...

 Block 252, referred to as the Macondo Prospect
Macondo Prospect
The Macondo Prospect is an oil and gas prospect in the United States Exclusive Economic Zone of the Gulf of Mexico, off the coast of Louisiana...

, in the United States sector of the Gulf of Mexico, about 41 miles (66 km) off the Louisiana coast. In March 2008, the mineral rights to drill for oil on the Macondo Prospect were purchased by BP at the Minerals Management Service
Minerals Management Service
The Bureau of Ocean Energy Management, Regulation and Enforcement , formerly known as the Minerals Management Service , was an agency of the United States Department of the Interior that managed the nation's natural gas, oil and other mineral resources on the outer continental shelf...

's lease sale. The platform commenced drilling in February 2010 at a water depth of approximately 5000 feet (1,524 m). At the time of the explosion the rig was drilling an exploratory well. The planned well was to be drilled to 18360 feet (5,596.1 m) below sea level, and was to be plugged and suspended for subsequent completion as a subsea producer. Production casing was being run and cemented at the time of the accident. Once the cementing was complete, it was due to be tested for integrity and a cement plug set to temporarily abandon the well for later completion as a subsea producer.

Transocean safety record

The rig owner, Transocean, had a "strong overall" safety record with no major incidents for 7 years. However an analysts' review "painted a more equivocal picture" with Transocean rigs being disproportionately responsible for safety related incidents in the Gulf and industry surveys reporting concerns over falling quality and performance. In the 3 years 2005 to 2007 Transocean was the owner of 30% of oilrigs active in the Gulf and 33% of incidents that triggered an MMS investigation were on Transocean rigs, but in the 3 years from 2008 to 15 February 2010 it owned 42% of rigs but was the owner for nearly 3/4 (73%) of incidents. Industry surveys saw this as an effect of its November 2007 merger with rival GlobalSantaFe. Transocean "has had problems" with both cement seals (2005) and blowout preventers (2006), which are the suspected cause of the Deepwater Horizon loss, although Transocean states cementing is a third party task and it has "a strong maintenance program to keep blowout preventers working". According to the Wall Street Journal online:
"In 2008 and 2009, the surveys ranked Transocean last among deep-water drillers for "job quality" and second to last in 'overall satisfaction'. For three years before the merger, Transocean was the leader or near the top in both measures. Transocean ranked first in 2008 and 2009 in a category that gauges its in-house safety and environmental policies"

"There were few indications of any trouble with the Deepwater Horizon before the explosion. The rig won an award from the MMS for its 2008 safety record, and on the day of the disaster, BP and Transocean managers were on board to celebrate seven years without a lost-time accident. Toby Odone, a BP spokesman, said rigs hired by BP have had better safety records than the industry average for six years running, according to MMS statistics that measure the number of citations per inspection. BP has been a finalist for a national safety award from the MMS for the past two years. Mr. Odone wouldn't comment on BP's relationship with Transocean after the Gulf disaster but said BP continues to use Transocean rigs."

Pre-explosion risks and precautions

In February 2009, BP filed a 52 page exploration and environmental impact plan for the Macondo well with the Minerals Management Service
Minerals Management Service
The Bureau of Ocean Energy Management, Regulation and Enforcement , formerly known as the Minerals Management Service , was an agency of the United States Department of the Interior that managed the nation's natural gas, oil and other mineral resources on the outer continental shelf...

 (MMS), an arm of the United States Department of the Interior
United States Department of the Interior
The United States Department of the Interior is the United States federal executive department of the U.S. government responsible for the management and conservation of most federal land and natural resources, and the administration of programs relating to Native Americans, Alaska Natives, Native...

 that oversees offshore drilling. The plan stated that it was "unlikely that an accidental surface or subsurface oil spill would occur from the proposed activities". In the event an accident did take place the plan stated that due to the well being 48 miles (77.2 km) from shore and the response capabilities that would be implemented, no significant adverse impacts would be expected.
The Department of the Interior exempted BP's Gulf of Mexico drilling operation from a detailed environmental impact study after concluding that a massive oil spill was unlikely.
In addition, following a loosening of regulations in 2008, BP was not required to file a detailed blowout plan.

The BP wellhead
Wellhead
A wellhead is a general term used to describe the component at the surface of an oil or gas well that provides the structural and pressure-containing interface for the drilling and production equipment....

 had been fitted with a blowout preventer
Blowout preventer
A blowout preventer is a large, specialized valve used to seal, control and monitor oil and gas wells. Blowout preventers were developed to cope with extreme erratic pressures and uncontrolled flow emanating from a well reservoir during drilling. Kicks can lead to a potentially catastrophic...

 (BOP), but it was not fitted with remote-control or acoustically activated triggers for use in case of an emergency requiring a platform to be evacuated. It did have a dead man's switch
Dead man's switch
A dead man's switch is a switch that is automatically operated in case the human operator becomes incapacitated, such as through death or loss of consciousness....

 designed to automatically cut the pipe and seal the well if communication from the platform is lost, but it was unknown whether the switch was activated.
Documents discussed during congressional hearings June 17, 2010 indicated that Transocean previously made modifications to the BOP for the Macondo site which increased the risk of BOP failure, in spite of warnings from their contractor to that effect. Regulators in both Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...

 and Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...

 generally require acoustically activated triggers on all offshore platforms, but when the Minerals Management Service considered requiring the remote device, a report commissioned by the agency as well as drilling companies questioned its cost and effectiveness.
In 2003, the agency determined that the device would not be required because drilling rigs had other back-up systems to cut off a well.

Pre-explosion problems and warnings

There had been previous spills and fires on the Deepwater Horizon; the US Coast Guard had issued pollution citations 18 times between 2000 and 2010, and had investigated 16 fires and other incidents. The previous fires, spills, and incidents were not considered unusual for a Gulf platform and have not been connected to the April, 2010 explosion and spill.
The Deepwater Horizon did, however, have other serious incidents, including one in 2008 in which 77 people were evacuated from the platform when it listed and began to sink after a section of pipe was accidentally removed from the platform's ballast
Ballast tank
A ballast tank is a compartment within a boat, ship or other floating structure that holds water.-History:The basic concept behind the ballast tank can be seen in many forms of aquatic life, such as the blowfish or argonaut octopus, and the concept has been invented and reinvented many times by...

 system.
By April 20, 2010 the Deepwater Horizon well operation was already running five weeks late. Internal BP documents show that BP engineers had concerns as early as 2009 that the metal casing BP wanted to use might collapse under high pressure.
In March 2010, the rig experienced problems that included drilling mud
Drilling fluid
In geotechnical engineering, drilling fluid is a fluid used to aid the drilling of boreholes into the earth. Often used while drilling oil and natural gas wells and on exploration drilling rigs, drilling fluids are also used for much simpler boreholes, such as water wells. Liquid drilling fluid...

 falling into the undersea oil formation, sudden gas releases, a pipe falling into the well, and at least three occasions of the blowout preventer leaking fluid.
The rig's mechanic stated that the well had problems for months and that the drill repeatedly kicked due to high gas pressure providing resistance. A confidential survey commissioned by Transocean weeks before the explosion states that workers were concerned about safety practices and feared reprisals if they reported mistakes or other problems. On the day the rig exploded, 79 of the 126 people on the rig were Transocean employees.

According to a report by 60 Minutes
60 Minutes
60 Minutes is an American television news magazine, which has run on CBS since 1968. The program was created by producer Don Hewitt who set it apart by using a unique style of reporter-centered investigation....

, the blowout preventer was damaged in a previously unreported accident in late March 2010. The American Bureau of Shipping
American Bureau of Shipping
The American Bureau of Shipping is a classification society, with a mission to promote the security of life, property and the natural environment, primarily through the development and verification of standards for the design, construction and operational maintenance of marine-related facilities...

 last inspected the rig's failed blowout preventer in 2005.
According to Transocean, workers had been performing standard routines and had no indication of any problems prior to the explosion.
Preliminary findings from BP’s internal investigation released by the House Committee on Energy and Commerce on May 25, 2010 indicated several serious warning signs in the hours just prior to the explosion.
Equipment readings indicated gas bubbling into the well, which could signal an impending blowout.
The heavy drilling mud
Drilling fluid
In geotechnical engineering, drilling fluid is a fluid used to aid the drilling of boreholes into the earth. Often used while drilling oil and natural gas wells and on exploration drilling rigs, drilling fluids are also used for much simpler boreholes, such as water wells. Liquid drilling fluid...

 in the pipes initially held down the gas of the leaking well.
A BP official onboard the rig directed the crew to replace the drilling mud, which is used to keep the well's pressure down, with lighter seawater even though the rig's chief driller protested.
According to a number of rig workers, it was understood that workers could get fired for raising safety concerns that might delay drilling.

On March 10, 2010, a BP executive e-mailed the Minerals Management Service
Minerals Management Service
The Bureau of Ocean Energy Management, Regulation and Enforcement , formerly known as the Minerals Management Service , was an agency of the United States Department of the Interior that managed the nation's natural gas, oil and other mineral resources on the outer continental shelf...

 that there was a stuck pipe and well control situation at the drilling site, and that BP would have to plugback the well.
A draft of a BP memo in April 2010 warned that the cementing of the casing was unlikely to be successful.
Halliburton
Halliburton
Halliburton is the world's second largest oilfield services corporation with operations in more than 70 countries. It has hundreds of subsidiaries, affiliates, branches, brands and divisions worldwide and employs over 50,000 people....

 has said that it had finished cementing 20 hours before the fire, but had not yet set the final cement plug.
A special nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...

-foamed cement was used which is more difficult to handle than standard cement.

A House Energy and Commerce Committee statement in June 2010 noted that in a number of cases leading up to the explosion, BP appears to have chosen riskier procedures to save time or money, sometimes against the advice of its staff or contractors.

On July 22, Sky News
Sky News
Sky News is a 24-hour British and international satellite television news broadcaster with an emphasis on UK and international news stories.The service places emphasis on rolling news, including the latest breaking news. Sky News also hosts localised versions of the channel in Australia and in New...

 reported that in a survey commissioned by Transocean workers on Deepwater Horizon raised concerns "about poor equipment reliability, which they believed was a result of drilling priorities taking precedence over maintenance."
The survey, carried out in March 2010, "less than half of the workers interviewed said they felt they could report actions leading to a potentially "risky" situation without any fear of reprisal ... many workers entered fake data to try to circumvent the system. As a result, the company's perception of safety on the rig was distorted, the report concluded."

On July 23, 2010 The New York Times reported that crew members had appeared before a federal panel of investigators, saying that power failures, computer crashes and emergency equipment leaks had occurred within a few weeks of the explosion.

Explosion and fire

The fire aboard the Deepwater Horizon reportedly started at CDT on April 20, 2010.
At the time, there were 126 crew on board: seven employees of BP, 79 of Transocean, as well as employees of various other companies involved in the operation of the rig, including Anadarko
Anadarko Petroleum Corporation
Anadarko Petroleum Corporation is one of the world’s largest independent oil and gas exploration and production companies, with approximately 2.3 billion barrels of oil equivalent of proved reserves and production of 206 million BOE as of December 31, 2008. Anadarko employs a worldwide...

, Halliburton and M-I Swaco.

Transocean employees on the vessel state that the lights flickered, followed by two strong vibrations. Transocean employee Jim Ingram stated that "on the second [thud], we knew something was wrong." After the explosion, Transocean executive Adrian Rose stated that abnormal pressure had accumulated inside the marine riser and as it came up it "expanded rapidly and ignited." According to interviews with platform workers conducted during BP's internal investigation, a bubble of methane
Methane
Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...

 gas escaped from the well and shot up the drill column, expanding quickly as it burst through several seals and barriers before exploding. Rose said the event was basically a blowout
Blowout (well drilling)
A blowout is the uncontrolled release of crude oil and/or natural gas from an oil well or gas well after pressure control systems have failed....

.
Survivors described the incident as a sudden explosion which gave them less than five minutes to escape as the alarm went off.

The explosion was followed by a fire that engulfed the platform. After burning for more than a day, Deepwater Horizon sank on April 22, 2010. The Coast Guard stated to CNN on April 22, 2010 that they received word of the sinking at approximately .

BP subsequently produced a report that suggests that the ignition source for the explosion and subsequent fire was as a result of the released hydrocarbons being ingested into the air intakes of the diesel generators, and engulfing the deck area where the exhaust outlets for the main generators were emitting hot exhaust gas. Had the engines been fitted with automatic combustion inlet shutdown valves, Pyroban
Pyroban
Pyroban began as a project implemented by Imperial Chemical Industries after the accidental release and ignition of a flammable vapour by a diesel engine at its Wilton Plant in the UK in 1969....

 kits, or executive gas detection systems that shutdown generator room HVAC systems automatically, the diesel engine ignition source could have been mitigated by breaking the fire triangle
Fire triangle
The fire triangle or combustion triangle is a simple model for understanding the ingredients necessary for most fires.The triangle illustrates a fire requires three elements: heat, fuel, and an oxidizing agent . The fire is prevented or extinguished by removing any one of them...

.

However, whilst these precautionary techniques are common throughout the North Sea, Asia Pacific, India, West Africa and parts of Australia, the operators in the GOM region continue to adopt the bare minimum of precaution without breaking local compliance laws laid down by MMS or Bureau of Ocean Energy Management, Regulation and Enforcement and the associated inspectorates such as ABS
American Bureau of Shipping
The American Bureau of Shipping is a classification society, with a mission to promote the security of life, property and the natural environment, primarily through the development and verification of standards for the design, construction and operational maintenance of marine-related facilities...

 who will only recognise electrical ignition hazards in line with the recommendations made in API 500/ NFPA 500 / and NEC 500.

Casualties and rescue efforts

Survivors

According to officials, 126 individuals were on board, of whom 79 were Transocean employees, six were from BP, and 41 were contracted; of these, 115 individuals were evacuated.
Most of the workers evacuated the rig and took diesel-powered fiberglass
Fiberglass
Glass fiber is a material consisting of numerous extremely fine fibers of glass.Glassmakers throughout history have experimented with glass fibers, but mass manufacture of glass fiber was only made possible with the invention of finer machine tooling...

 lifeboats
Lifeboat (shipboard)
A lifeboat is a small, rigid or inflatable watercraft carried for emergency evacuation in the event of a disaster aboard ship. In the military, a lifeboat may be referred to as a whaleboat, dinghy, or gig. The ship's tenders of cruise ships often double as lifeboats. Recreational sailors sometimes...

 to the M/V Damon B Bankston, a workboat that BP had hired to service the rig.
Seventeen others were then evacuated from the workboat by helicopter.
Most survivors were brought to Port Fourchon
Port Fourchon, Louisiana
Port Fourchon is Louisiana’s southernmost port, located on the southern tip of Lafourche Parish, Louisiana, on the Gulf of Mexico. It is a sea port, with significant petroleum industry traffic from offshore Gulf oil platforms and drilling rigs as well as the Louisiana Offshore Oil Port pipeline...

 for a medical check-up and to meet their families.
Although 94 workers were taken to shore with no major injuries, four were transported to another vessel, and 17 were sent to trauma centers in Mobile, Alabama and Marrero, Louisiana
Marrero, Louisiana
Marrero is a census-designated place in Jefferson Parish, Louisiana, United States. Marrero is on the West Bank of the Mississippi River, within the New Orleans–Metairie–Kenner Metropolitan Statistical Area...

. Most were soon released.
When the blowout occurred, 4 BP and Transocean executives were on board the platform for a tour of the rig, maintenance planning, annual goals review, a "Drops" safety campaign, and to congratulate the senior staff of the rig for 7 years of operations without a lost time incident (MMS reports show a lost time accident occurred 2008-03-06 on a service vessel at a lease being worked by the Deepwater Horizon, in preparation for a crane operation under control of the Deepwater Horizon); they were injured but survived.
Lawyers for some survivors of the blast claim that their clients were kept in boats and on another rig for 15 hours or more before being brought to shore and when they did get to shore, "they were zipped into private buses, there was security there, there was no press, no lawyers allowed, nothing, no family members."
They were then driven to a hotel under escort, secluded at the hotel for hours, questioned by company consultants and investigators and then given a form to sign before being released.
These claims are denied by Transocean.

Casualities

Initial reports indicated that between 12 to 15 workers were missing; reports soon narrowed the number of missing to nine crew members on the platform floor and two engineers. The United States Coast Guard
United States Coast Guard
The United States Coast Guard is a branch of the United States Armed Forces and one of the seven U.S. uniformed services. The Coast Guard is a maritime, military, multi-mission service unique among the military branches for having a maritime law enforcement mission and a federal regulatory agency...

 immediately launched a massive rescue operation involving two Coast Guard cutters
United States Coast Guard Cutter
Cutter is the term used by the United States Coast Guard for its commissioned vessels. A Cutter is or greater in length, has a permanently assigned crew, and has accommodations for the crew to live aboard...

, four helicopters, and a rescue plane. Two of the cutters continued searching through the night. By the morning of April 22, the Coast Guard had surveyed nearly 1940 mi2. On April 23, the Coast Guard called off the search for the 11 missing persons, concluding that "reasonable expectations of survival" had passed. Officials concluded that the missing workers may have been near the blast and unable to escape the sudden explosion. Jason C. Anderson, 35, Aaron Dale Burkeen, 37, Donald Clark, 49, Stephen Ray Curtis, 39, Roy Wyatt Kemp, 27, Karl D. Kleppinger Jr., 38, Gordon L. Jones, Keith Blair Manuel, 56, Dewey A. Revette, 48,
Shane M. Roshto, 22, and Adam Weise, 24, died that day.

Discovery of oil spill

On the morning of April 22, 2010 (two days after the blowout accident), CNN quoted Coast Guard Petty Officer Ashley Butler as saying that "oil was leaking from the rig at the rate of about 8000 bbl (336,000 US gal; 1,271,898.4 l) of crude per day."
That afternoon, as a large oil slick spread, Coast Guard Senior Chief Petty Officer Michael O'Berry used the same figure. Two remotely operated underwater vehicles (ROVs) were sent down to attempt to cap the well, but had been unsuccessful. Butler warned of a leak of up to 700000 gallons (16,666.7 bbl) of diesel fuel, and BP Vice President David Rainey termed the incident as being a potential "major spill."

On April 22, 2010, BP announced that it was deploying a remotely operated underwater vehicle to the site to assess whether oil was flowing from the well.
Other reports indicated that BP was using more than one remotely operated underwater vehicle and that the purpose was to attempt to plug the well pipe.
On April 23, 2010, a remotely operated underwater vehicle reportedly found no oil leaking from the sunken rig and no oil flowing from the well.
Coast Guard Rear Admiral
Rear admiral (United States)
Rear admiral is a naval commissioned officer rank above that of a commodore and captain, and below that of a vice admiral. The uniformed services of the United States are unique in having two grades of rear admirals.- Rear admiral :...

  Mary Landry
Mary Landry
Mary E. Landry is a Rear Admiral in the United States Coast Guard. Rear Admiral Mary E. Landry serves as the Commander of the Eighth Coast Guard District and Commander of Task Force 189.8, headquartered in New Orleans. As District Commander, Rear Admiral Landry is responsible for U.S...

 expressed cautious optimism of zero environmental impact, stating that no oil was emanating from either the wellhead or the broken pipes and that oil spilled from the explosion and sinking was being contained.
The following day, April 24, 2010, Landry announced that a damaged wellhead was indeed leaking oil into the Gulf and described it as "a very serious spill".

Investigation into explosion

At an April 30, 2010 press conference, BP said that it did not know the cause of the explosion. Transocean chief executive Steven Newman described the cause as "a sudden, catastrophic failure of the cement, the casing or both."
President Barack Obama
Barack Obama
Barack Hussein Obama II is the 44th and current President of the United States. He is the first African American to hold the office. Obama previously served as a United States Senator from Illinois, from January 2005 until he resigned following his victory in the 2008 presidential election.Born in...

 authorized SWAT (Surface Water Assessment Team of the Minerals Management Service, part of U.S. Dept. of Interior) teams to investigate 29 oil rigs in the Gulf in an effort to determine the cause of the disaster.
On May 11, 2010, Department of the Interior released a press release, announcing that the inspection of deepwater drilling rigs in the Gulf of Mexico found no major violations.
There are ongoing investigations to determine the root causes of the disaster.

In June, the House Committee on Energy and Commerce said BP should have tested cement at the well, which would have cost $128,000 and taken 8–12 hours.

On September 8, 2010, BP released a 193-page report on its web site. The report says BP employees and those of Transocean
Transocean
Transocean Ltd. is one of the world's largest offshore drilling contractors. The company rents floating mobile drill rigs, along with the equipment and personnel for operations, to oil and gas companies at an average daily rate of US$282,700...

 did not correctly interpret a pressure test, and both companies neglected ominous signs such as a pipe called a riser losing fluid. It also says that while BP did not listen to recommendations by Halliburton
Halliburton
Halliburton is the world's second largest oilfield services corporation with operations in more than 70 countries. It has hundreds of subsidiaries, affiliates, branches, brands and divisions worldwide and employs over 50,000 people....

 for more centralizers, the lack of centralizers probably did not affect the cement. BP also said the crew should have redirected the flow of flammable gases. The blowout preventer, removed on September 4, had not reached a NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...

 facility in time for it to be part of the report. Transocean, responding to the report, blamed "BP's fatally flawed well design."

On November 8, 2010, the inquiry by the Oil Spill Commission revealed its findings that BP had not sacrificed safety in attempts to make money, but that some decisions had increased risks on the rig. However, the panel said a day later that there had been "a rush to completion" on the well, criticizing poor management decisions. "There was not a culture of safety on that rig," co-chair Bill Reilly said. One of the decisions met with tough questions was that BP refuted the findings of advanced modelling software that had ascertained over three times as many centralizers were needed on the rig. It also decided not to rerun the software when it stuck with only six centralizers, and ignored or misread warnings from other key tests, the panel revealed.

A slide briefly appeared on the Oil Spill Commission’s website which enumerated eight “risky” and “unnecessary” steps that BP was deemed to have taken. The New York Times newspaper has published a screenshot of the slide here.

Disposition of financial obligation

On April 21, 2011, BP filed $40bn worth of lawsuits against rig owner Transocean, cementer Halliburton and blowout-preventer manufacturer Cameron
Cameron International Corporation
Cameron International Corporation , , is a Fortune 500 company and a global provider of pressure control, processing, flow control and compression systems as well as project management and aftermarket services for the oil and gas and process industries...

. The oil firm alleged that failed safety systems and irresponsible behaviour of contractors had led to the explosion, including claims that Halliburton "negligently" failed to use cement-modelling software OptiCem properly to analyze safe well requirements. Part of the modelling concern was about the number of stabilising devices, known as centralisers, the well required: 21 called-for v. 6 used.

In May, 2011, MOEX Offshore, which owned a 10% stake in the well through a subsidiary and which in turn itself was majority-owned by Mitsui & Co.
Mitsui & Co.
Mitsui & Co., also known as Mitsui Bussan, is one of the largest sogo shosha in Japan, and also part of the Mitsui Group. Its business area covers energy, machinery, chemicals, food, textile, logistics, finance, and more.- History :...

, agreed to pay US$1.07 billion to settle BP claims against it over the accident. Some analysts had thought BP would realize a larger settlement from MOEX but there was also relief to have a first step toward resolving the multiple claims. BP’s most recent estimate at the time was that the spill would cost $41.3 billion. Anadarko Petroleum held a 25% stake in the Macondo well and was an immediate focus of attention with MOEX's agreement. Also the Department of Justice
United States Department of Justice
The United States Department of Justice , is the United States federal executive department responsible for the enforcement of the law and administration of justice, equivalent to the justice or interior ministries of other countries.The Department is led by the Attorney General, who is nominated...

 was still at the time investigating whether BP was "grossly negligent" in the spill. Such a determination could lead to a "much larger liability under the Clean Water Act
Clean Water Act
The Clean Water Act is the primary federal law in the United States governing water pollution. Commonly abbreviated as the CWA, the act established the goals of eliminating releases of high amounts of toxic substances into water, eliminating additional water pollution by 1985, and ensuring that...

,” a financial analyst said. With MOEX agreeing to share in the financial burden—though "the agreement isn’t an admission of liability by either party" -- the possibility of such a ruling by DOJ seemed to some to be perhaps lessened.

In October 2011, Anadarko Petroleum Corporation
Anadarko Petroleum Corporation
Anadarko Petroleum Corporation is one of the world’s largest independent oil and gas exploration and production companies, with approximately 2.3 billion barrels of oil equivalent of proved reserves and production of 206 million BOE as of December 31, 2008. Anadarko employs a worldwide...

 agreed to pay BP $4 billion and the two companies settled all claims between them. Anadarko yielded its 25% stake in Mississippi Canyon Block 252 (Macondo) to BP in the agreement and BP will indemnify Anadarko for damage claims arising under the U.S. Oil Pollution Act
Oil Pollution Act of 1990
The Oil Pollution Act was passed by the 101st United States Congress, and signed by President George H. W. Bush, to mitigate and prevent civil liability for future oil spills off the coast of the United States....

, among other costs.

See also

  • Timeline of the Deepwater Horizon oil spill
    Timeline of the Deepwater Horizon oil spill
    The following is a timeline of the Deepwater Horizon oil spill . It was a massive oil spill in the Gulf of Mexico, the largest offshore spill in U.S. history...

  • Ixtoc I oil spill
  • Offshore oil and gas in the US Gulf of Mexico
    Offshore oil and gas in the US Gulf of Mexico
    Offshore oil and gas in the US Gulf of Mexico is a major source of oil and natural gas in the United States. The western and central Gulf of Mexico, which includes offshore Texas, Louisiana, Mississippi, and Alabama, is one of the major petroleum-producing areas of the United States...


External links

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