🕷️ Crawler Inspector

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Raw Queries and Responses

1. Shard Calculation

Query:

Response:

Calculated Shard: 9 (from laksa148)

2. Crawled Status Check

Query:

curl -X POST \
  'http://laksa009.int.ahrefs:8124/' \
  -H 'Content-Type: text/plain' \
  -H 'X-ClickHouse-Database: crawler3' \
  -H 'Authorization: Basic YXBpOg==' \
  -d 'SELECT getAhrefsURLFromUnparsed(src_unparsed) AS found_url, ifNull(toUnixTimestamp(download_stamp), 0) AS crawl_time, ifNull(toUnixTimestamp(props_url_first_seen), 0) AS first_indexed_time, download_http_code AS http_code, src_unparsed AS src_unparsed, src_root_hash AS src_root_hash, history_drop_reason AS history_drop_reason, meta_title AS meta_title, meta_descriptions AS meta_descriptions, attrs_boilerpipe_text AS attrs_boilerpipe_text, attrs_markdown AS attrs_markdown, attrs_readable_markdown AS attrs_readable_markdown, meta_canonical AS meta_canonical FROM crawler3.page_info_local FINAL PREWHERE (src_root_hash, src_unparsed) IN ((getAhrefsRootHashFromUnparsed(getAhrefsUnparsedNoserviceFromURL(\'https://www.newscientist.com/article/dn19425-the-eight-failures-that-caused-the-gulf-oil-spill/\')), getAhrefsUnparsedNoserviceFromURL(\'https://www.newscientist.com/article/dn19425-the-eight-failures-that-caused-the-gulf-oil-spill/\'))) FORMAT JSONEachRow'

Response:

{"found_url":"https:\/\/www.newscientist.com\/article\/dn19425-the-eight-failures-that-caused-the-gulf-oil-spill\/","crawl_time":1774922100,"first_indexed_time":1439609743,"http_code":200,"src_unparsed":"com,newscientist!www,\/article\/dn19425-the-eight-failures-that-caused-the-gulf-oil-spill\/ s443","src_root_hash":"443924557768237609","history_drop_reason":null,"meta_title":"The eight failures that caused the Gulf oil spill | New Scientist","meta_descriptions":["Eight catastrophic failures led to the explosion that destroyed the Deepwater Horizon drilling rig in the Gulf of Mexico, killing 11 people and leading to one of the biggest oil leaks in history , according to BP's long-awaited investigation into the accident . BP accepts its role in the disaster but also points the finger …"],"attrs_boilerpipe_text":"Eight catastrophic failures led to the explosion that destroyed the Deepwater Horizon drilling rig in the Gulf of Mexico, killing 11 people and leading to one of the\nbiggest oil leaks in history\n, according to\nBP’s long-awaited investigation into the accident\n.\nBP accepts its role in the disaster but also points the finger at two of its contractors.\nThe\naccident occurred on 20 April\nas the team aboard Deepwater Horizon was preparing to temporarily abandon a well it had drilled some 70 kilometres from the US coast.\nThe day before the accident, the crew had pumped cement to the bottom of the borehole, a standard procedure intended to prevent oil leaking out. On the day of the accident, the team were conducting checks to determine that that the well had been properly sealed.\nBP says the accident was caused by the failure of eight different safety systems that were meant to prevent this kind of incident:\nDodgy cement\nThe cement at the bottom of the borehole did not create a seal, and oil and gas began to leak through it into the pipe leading to the surface. BP says the cement formulation seems not to have been up to the job.\nValve failure\nThe bottom of the pipe to the surface was sealed in two ways. It too was filled with cement, and it also contained two mechanical valves designed to stop the flow of oil and gas. All of these failed, allowing oil and gas to travel up the pipe towards the surface.\nPressure test misinterpreted\nThe crew carried out various pressure tests to determine whether the well was sealed or not. The results of these tests were misinterpreted, so they thought the well was under control.\nLeak not spotted soon enough\nWhether a well is under control or not, the crew at the surface should be able to detect a flow of oil and gas towards the surface by looking for unexpected increases in pressure in the well. Exactly this kind of increase occurred about 50 minutes before the rig exploded, but it was not interpreted as a leak.\nValve failure no. 2\nAbout 8 minutes before the explosion, a mixture of mud and gas began pouring onto the floor of the rig. The crew immediately attempted to close a valve in a device called the blowout preventer, which sits on the ocean floor over the top of the well borehole. It did not work properly.\nOverwhelmed separator\nThe crew had the option of diverting the mud and gas away from the rig, venting it safely through pipes over the side. Instead, the flow was diverted to a device on board the rig designed to separate small amounts of gas from a flow of mud. The so-called mud-gas separator was quickly overwhelmed and flammable gas began to engulf the rig.\nNo gas alarm\nThe rig had an onboard gas detection system that should have sounded the alarm and triggered the closure of ventilation fans to prevent the gas reaching potential causes of ignition, such as the rig’s engines. This system failed.\nNo battery for BOP\nThe explosion destroyed the control lines the crew were using to attempt to close safety valves in the blowout preventer. However, the blowout preventer has its own safety mechanism in which two separate systems should have shut the valves automatically when it lost contact with the surface. One system seems to have had a flat battery and the other a defective switch. Consequently, the blowout preventer did not close.\n“It is evident that a series of complex events, rather than a single mistake or failure, led to the tragedy. Multiple parties, including BP, [oilfield services company] Halliburton and [offshore drilling company] Transocean, were involved,” said Tony Hayward, BP’s chief executive.\nTopics:","attrs_markdown":"Close\n\nAdvertisement\n\n[Skip to content](https:\/\/www.newscientist.com\/article\/dn19425-the-eight-failures-that-caused-the-gulf-oil-spill\/#first-link)\n\n[Sign in](https:\/\/www.newscientist.com\/login\/ \"Sign In page link\")\n\nLight\n\n- [Curiosity engine](https:\/\/www.newscientist.com\/curiosity-engine)\n- [Events](https:\/\/www.newscientist.com\/science-events\/)\n- [Tours](https:\/\/www.newscientist.com\/tours\/)\n- [Shop](https:\/\/shop.newscientist.com\/)\n\n[Subscribe now](https:\/\/subscription.newscientist.com\/packages\/p\/cms\/TB)\n\n### Explore by section\n- [News](https:\/\/www.newscientist.com\/section\/news\/)\n- [Features](https:\/\/www.newscientist.com\/section\/features\/)\n- [Newsletters](https:\/\/www.newscientist.com\/sign-up\/)\n- [Podcasts](https:\/\/www.newscientist.com\/podcasts\/)\n- [Video](https:\/\/www.newscientist.com\/video\/)\n- [Comment](https:\/\/www.newscientist.com\/section\/comment\/)\n- [Culture](https:\/\/www.newscientist.com\/section\/culture\/)\n- [Games](https:\/\/www.newscientist.com\/games\/)\n- \\|\n- [This week's magazine](https:\/\/www.newscientist.com\/issues\/current\/)\n\n### Explore by subject\n- [Health](https:\/\/www.newscientist.com\/subject\/health\/)\n- [Space](https:\/\/www.newscientist.com\/subject\/space\/)\n- [Physics](https:\/\/www.newscientist.com\/subject\/physics\/)\n- [Technology](https:\/\/www.newscientist.com\/subject\/technology\/)\n- [Environment](https:\/\/www.newscientist.com\/subject\/environment\/)\n- [Mind](https:\/\/www.newscientist.com\/subject\/mind\/)\n- [Humans](https:\/\/www.newscientist.com\/subject\/humans\/)\n- [Life](https:\/\/www.newscientist.com\/subject\/life\/)\n- [Mathematics](https:\/\/www.newscientist.com\/subject\/mathematics\/)\n- [Chemistry](https:\/\/www.newscientist.com\/subject\/chemistry\/)\n- [Earth](https:\/\/www.newscientist.com\/subject\/earth\/)\n- [Society](https:\/\/www.newscientist.com\/subject\/society\/)\n\n### Explore our products and services\n- [Curiosity engine](https:\/\/www.newscientist.com\/curiosity-engine)\n- [Events](https:\/\/www.newscientist.com\/science-events\/)\n- [Tours](https:\/\/www.newscientist.com\/tours\/)\n- [Shop](https:\/\/shop.newscientist.com\/)\n\n[Subscribe now](https:\/\/subscription.newscientist.com\/packages\/p\/cms\/TB)\n\n[Subscribe now](https:\/\/subscription.newscientist.com\/packages\/p\/cms\/TB)\n\n#### [Earth](https:\/\/www.newscientist.com\/subject\/earth\/)\n# The eight failures that caused the Gulf oil spill\nBy [Justin Mullins](https:\/\/www.newscientist.com\/author\/justin-mullins\/)\n\n8 September 2010\n\nEight catastrophic failures led to the explosion that destroyed the Deepwater Horizon drilling rig in the Gulf of Mexico, killing 11 people and leading to one of the [biggest oil leaks in history](https:\/\/www.newscientist.com\/special\/deepwater-horizon-oil-spill), according to [BP’s long-awaited investigation into the accident](http:\/\/www.bp.com\/liveassets\/bp_internet\/globalbp\/globalbp_uk_english\/incident_response\/STAGING\/local_assets\/downloads_pdfs\/Deepwater_Horizon_Accident_Investigation_Report.pdf).\n\nBP accepts its role in the disaster but also points the finger at two of its contractors.\n\nThe [accident occurred on 20 April](https:\/\/www.newscientist.com\/article\/mg20627595-100-oil-slick-fight-continues-with-robots-and-fire) as the team aboard Deepwater Horizon was preparing to temporarily abandon a well it had drilled some 70 kilometres from the US coast.\n\nThe day before the accident, the crew had pumped cement to the bottom of the borehole, a standard procedure intended to prevent oil leaking out. On the day of the accident, the team were conducting checks to determine that that the well had been properly sealed.\n\nAdvertisement\n\nBP says the accident was caused by the failure of eight different safety systems that were meant to prevent this kind of incident:\n\n## Dodgy cement\nThe cement at the bottom of the borehole did not create a seal, and oil and gas began to leak through it into the pipe leading to the surface. BP says the cement formulation seems not to have been up to the job.\n\n## Valve failure\nThe bottom of the pipe to the surface was sealed in two ways. It too was filled with cement, and it also contained two mechanical valves designed to stop the flow of oil and gas. All of these failed, allowing oil and gas to travel up the pipe towards the surface.\n\n## Pressure test misinterpreted\nThe crew carried out various pressure tests to determine whether the well was sealed or not. The results of these tests were misinterpreted, so they thought the well was under control.\n\n## Leak not spotted soon enough\nWhether a well is under control or not, the crew at the surface should be able to detect a flow of oil and gas towards the surface by looking for unexpected increases in pressure in the well. Exactly this kind of increase occurred about 50 minutes before the rig exploded, but it was not interpreted as a leak.\n\n## Valve failure no. 2\nAbout 8 minutes before the explosion, a mixture of mud and gas began pouring onto the floor of the rig. The crew immediately attempted to close a valve in a device called the blowout preventer, which sits on the ocean floor over the top of the well borehole. It did not work properly.\n\n## Overwhelmed separator\nThe crew had the option of diverting the mud and gas away from the rig, venting it safely through pipes over the side. Instead, the flow was diverted to a device on board the rig designed to separate small amounts of gas from a flow of mud. The so-called mud-gas separator was quickly overwhelmed and flammable gas began to engulf the rig.\n\n## No gas alarm\nThe rig had an onboard gas detection system that should have sounded the alarm and triggered the closure of ventilation fans to prevent the gas reaching potential causes of ignition, such as the rig’s engines. This system failed.\n\n## No battery for BOP\nThe explosion destroyed the control lines the crew were using to attempt to close safety valves in the blowout preventer. However, the blowout preventer has its own safety mechanism in which two separate systems should have shut the valves automatically when it lost contact with the surface. One system seems to have had a flat battery and the other a defective switch. Consequently, the blowout preventer did not close.\n\n“It is evident that a series of complex events, rather than a single mistake or failure, led to the tragedy. Multiple parties, including BP, \\[oilfield services company\\] Halliburton and \\[offshore drilling company\\] Transocean, were involved,” said Tony Hayward, BP’s chief executive.\n\nTopics:\n\n- [environment](https:\/\/www.newscientist.com\/article-topic\/environment\/) \/\n- [Deepwater Horizon](https:\/\/www.newscientist.com\/article-topic\/deepwater-horizon\/)\/\n- [pollution](https:\/\/www.newscientist.com\/article-topic\/pollution\/)\/\n- [oil](https:\/\/www.newscientist.com\/article-topic\/oil\/)\n\nAdvertisement\n\n## Sign up to our weekly newsletter\nReceive a weekly dose of discovery in your inbox. We'll also keep you up to date with  *New Scientist*  events and special offers.\n\n[Sign up](https:\/\/www.newscientist.com\/sign-up\/weekly)\n\n## More from *New Scientist*\nExplore the latest news, articles and features\n\n[![](https:\/\/images.newscientist.com\/wp-content\/uploads\/2026\/02\/20133249\/SEI_285864477.jpg) Life Fish-based pet food may expose cats and dogs to forever chemicals News](https:\/\/www.newscientist.com\/article\/2516516-fish-based-pet-food-may-expose-cats-and-dogs-to-forever-chemicals\/)\n\n[![](https:\/\/images.newscientist.com\/wp-content\/uploads\/2026\/02\/19145520\/SEI_285836324.jpg) Environment Atmospheric pollution caused by space junk could be a huge problem News](https:\/\/www.newscientist.com\/article\/2516338-atmospheric-pollution-caused-by-space-junk-could-be-a-huge-problem\/)\n\n[![Satellite-filled sky](https:\/\/images.newscientist.com\/wp-content\/uploads\/2025\/10\/08124959\/SEI_269483965.jpg) Earth How worried should we be about noxious chemicals from dead satellites? Features](https:\/\/www.newscientist.com\/article\/2499326-how-worried-should-we-be-about-noxious-chemicals-from-dead-satellites\/)\n\n[![](https:\/\/images.newscientist.com\/wp-content\/uploads\/2025\/07\/18161543\/SEI_259378106.jpg) Life Exposure to microplastic makes animals want to eat it more News](https:\/\/www.newscientist.com\/article\/2488923-exposure-to-microplastic-makes-animals-want-to-eat-it-more\/)\n\n#### Popular articles\nTrending *New Scientist* articles\n\n[1 The Shroud of Turin bears DNA from many people, plants and animals](https:\/\/www.newscientist.com\/article\/2521236-the-shroud-of-turin-bears-dna-from-many-people-plants-and-animals\/)\n\n[2 Surprising male G-spot found in most detailed study of the penis yet](https:\/\/www.newscientist.com\/article\/2520982-surprising-male-g-spot-found-in-most-detailed-study-of-the-penis-yet\/)\n\n[3 AI data centres can warm surrounding areas by up to 9.1°C](https:\/\/www.newscientist.com\/article\/2521256-ai-data-centres-can-warm-surrounding-areas-by-up-to-9-1c\/)\n\n[4 The profound effect the heart-brain connection has on your health](https:\/\/www.newscientist.com\/article\/2519667-the-profound-effect-the-heart-brain-connection-has-on-your-health\/)\n\n[5 Food shock is inevitable due to the Iran war – and it could get bad](https:\/\/www.newscientist.com\/article\/2521311-food-shock-is-inevitable-due-to-the-iran-war-and-it-could-get-bad\/)\n\n[6 The brain's cleaning system can be boosted to rid Alzheimer's proteins](https:\/\/www.newscientist.com\/article\/2520849-the-brains-cleaning-system-can-be-boosted-to-rid-alzheimers-proteins\/)\n\n[7 The weird physics of plant-based milks is only just coming to light](https:\/\/www.newscientist.com\/article\/2521037-the-weird-physics-of-plant-based-milks-is-only-just-coming-to-light\/)\n\n[8 The shocking fossils that show T. rex wasn't the king of the dinosaurs](https:\/\/www.newscientist.com\/article\/2519003-the-shocking-fossils-that-show-t-rex-wasnt-the-king-of-the-dinosaurs\/)\n\n[9 How Anthony Leggett pushed the boundaries of quantum physics](https:\/\/www.newscientist.com\/article\/2521212-how-anthony-leggett-pushed-the-boundaries-of-quantum-physics\/)\n\n[10 How working out like an astronaut can reduce back pain and slow ageing](https:\/\/www.newscientist.com\/article\/2519666-how-working-out-like-an-astronaut-can-reduce-back-pain-and-slow-ageing\/)\n\nAdvertisement\n\n[![Piano End Banner](https:\/\/images.newscientist.com\/wp-content\/uploads\/2024\/04\/17102106\/new-scientist-social-meta-image.png)]()\n\nClose\n\n[![Piano Exit Overlay Banner Mobile](https:\/\/images.newscientist.com\/wp-content\/uploads\/2024\/04\/17102106\/new-scientist-social-meta-image.png) ![Piano Exit Overlay Banner 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[Educational](https:\/\/landing.newscientist.com\/group-subscriptions\/)\n- [Corporate](https:\/\/landing.newscientist.com\/group-subscriptions\/)\n\n#### Support\n- [Contact us](https:\/\/www.newscientist.com\/contact-us\/)\n- [FAQs](https:\/\/www.newscientist.com\/help\/)\n- [About us](https:\/\/www.newscientist.com\/about\/)\n- [Press room](https:\/\/www.newscientist.com\/press-room\/)\n- [Advertise](https:\/\/experience.newscientist.com\/advertise)\n- [Write for us](https:\/\/www.newscientist.com\/freelancers\/)\n\n#### Tools\n- [Events](https:\/\/www.newscientist.com\/science-events\/)\n- [CoLab](https:\/\/colab.newscientist.com\/)\n- [Syndication](https:\/\/www.newscientist.com\/in216-syndication-information\/)\n- [RSS feeds](https:\/\/www.newscientist.com\/rss-feeds\/)\n\n#### Legal and privacy\n- [Complaint policy](https:\/\/www.newscientist.com\/complaint-policy\/)\n- [Privacy policy](https:\/\/www.newscientist.com\/privacy\/)\n- [Cookie policy](https:\/\/www.newscientist.com\/cookie-policy\/)\n- [Terms & conditions](https:\/\/www.newscientist.com\/terms\/)\n- Cookie Settings\n\n#### © Copyright New Scientist Ltd.\nBack to the top","attrs_readable_markdown":"Eight catastrophic failures led to the explosion that destroyed the Deepwater Horizon drilling rig in the Gulf of Mexico, killing 11 people and leading to one of the [biggest oil leaks in history](https:\/\/www.newscientist.com\/special\/deepwater-horizon-oil-spill), according to [BP’s long-awaited investigation into the accident](http:\/\/www.bp.com\/liveassets\/bp_internet\/globalbp\/globalbp_uk_english\/incident_response\/STAGING\/local_assets\/downloads_pdfs\/Deepwater_Horizon_Accident_Investigation_Report.pdf).\n\nBP accepts its role in the disaster but also points the finger at two of its contractors.\n\nThe [accident occurred on 20 April](https:\/\/www.newscientist.com\/article\/mg20627595-100-oil-slick-fight-continues-with-robots-and-fire) as the team aboard Deepwater Horizon was preparing to temporarily abandon a well it had drilled some 70 kilometres from the US coast.\n\nThe day before the accident, the crew had pumped cement to the bottom of the borehole, a standard procedure intended to prevent oil leaking out. On the day of the accident, the team were conducting checks to determine that that the well had been properly sealed.\n\nBP says the accident was caused by the failure of eight different safety systems that were meant to prevent this kind of incident:\n\n## Dodgy cement\nThe cement at the bottom of the borehole did not create a seal, and oil and gas began to leak through it into the pipe leading to the surface. BP says the cement formulation seems not to have been up to the job.\n\n## Valve failure\nThe bottom of the pipe to the surface was sealed in two ways. It too was filled with cement, and it also contained two mechanical valves designed to stop the flow of oil and gas. All of these failed, allowing oil and gas to travel up the pipe towards the surface.\n\n## Pressure test misinterpreted\nThe crew carried out various pressure tests to determine whether the well was sealed or not. The results of these tests were misinterpreted, so they thought the well was under control.\n\n## Leak not spotted soon enough\nWhether a well is under control or not, the crew at the surface should be able to detect a flow of oil and gas towards the surface by looking for unexpected increases in pressure in the well. Exactly this kind of increase occurred about 50 minutes before the rig exploded, but it was not interpreted as a leak.\n\n## Valve failure no. 2\nAbout 8 minutes before the explosion, a mixture of mud and gas began pouring onto the floor of the rig. The crew immediately attempted to close a valve in a device called the blowout preventer, which sits on the ocean floor over the top of the well borehole. It did not work properly.\n\n## Overwhelmed separator\nThe crew had the option of diverting the mud and gas away from the rig, venting it safely through pipes over the side. Instead, the flow was diverted to a device on board the rig designed to separate small amounts of gas from a flow of mud. The so-called mud-gas separator was quickly overwhelmed and flammable gas began to engulf the rig.\n\n## No gas alarm\nThe rig had an onboard gas detection system that should have sounded the alarm and triggered the closure of ventilation fans to prevent the gas reaching potential causes of ignition, such as the rig’s engines. This system failed.\n\n## No battery for BOP\nThe explosion destroyed the control lines the crew were using to attempt to close safety valves in the blowout preventer. However, the blowout preventer has its own safety mechanism in which two separate systems should have shut the valves automatically when it lost contact with the surface. One system seems to have had a flat battery and the other a defective switch. Consequently, the blowout preventer did not close.\n\n“It is evident that a series of complex events, rather than a single mistake or failure, led to the tragedy. Multiple parties, including BP, \\[oilfield services company\\] Halliburton and \\[offshore drilling company\\] Transocean, were involved,” said Tony Hayward, BP’s chief executive.\n\nTopics:","meta_canonical":null}

3. Robots.txt Check

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4. Spam/Ban Check

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5. Seen Status Check

ℹ️ Skipped - page is already crawled

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CRAWLED

17 days ago

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Page Info Filters

Filter	Status	Condition	Details
HTTP status	PASS	`download_http_code = 200`	HTTP 200
Age cutoff	PASS	`download_stamp > now() - 6 MONTH`	0.6 months ago
History drop	PASS	`isNull(history_drop_reason)`	No drop reason
Spam/ban	PASS	`fh_dont_index != 1 AND ml_spam_score = 0`	ml_spam_score=0
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URL	https://www.newscientist.com/article/dn19425-the-eight-failures-that-caused-the-gulf-oil-spill/
Last Crawled	2026-03-31 01:55:00 (17 days ago)
First Indexed	2015-08-15 03:35:43 (10 years ago)
HTTP Status Code	200
Meta Title	The eight failures that caused the Gulf oil spill \| New Scientist
Meta Description	Eight catastrophic failures led to the explosion that destroyed the Deepwater Horizon drilling rig in the Gulf of Mexico, killing 11 people and leading to one of the biggest oil leaks in history , according to BP's long-awaited investigation into the accident . BP accepts its role in the disaster but also points the finger …
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Boilerpipe Text	Eight catastrophic failures led to the explosion that destroyed the Deepwater Horizon drilling rig in the Gulf of Mexico, killing 11 people and leading to one of the biggest oil leaks in history , according to BP’s long-awaited investigation into the accident . BP accepts its role in the disaster but also points the finger at two of its contractors. The accident occurred on 20 April as the team aboard Deepwater Horizon was preparing to temporarily abandon a well it had drilled some 70 kilometres from the US coast. The day before the accident, the crew had pumped cement to the bottom of the borehole, a standard procedure intended to prevent oil leaking out. On the day of the accident, the team were conducting checks to determine that that the well had been properly sealed. BP says the accident was caused by the failure of eight different safety systems that were meant to prevent this kind of incident: Dodgy cement The cement at the bottom of the borehole did not create a seal, and oil and gas began to leak through it into the pipe leading to the surface. BP says the cement formulation seems not to have been up to the job. Valve failure The bottom of the pipe to the surface was sealed in two ways. It too was filled with cement, and it also contained two mechanical valves designed to stop the flow of oil and gas. All of these failed, allowing oil and gas to travel up the pipe towards the surface. Pressure test misinterpreted The crew carried out various pressure tests to determine whether the well was sealed or not. The results of these tests were misinterpreted, so they thought the well was under control. Leak not spotted soon enough Whether a well is under control or not, the crew at the surface should be able to detect a flow of oil and gas towards the surface by looking for unexpected increases in pressure in the well. Exactly this kind of increase occurred about 50 minutes before the rig exploded, but it was not interpreted as a leak. Valve failure no. 2 About 8 minutes before the explosion, a mixture of mud and gas began pouring onto the floor of the rig. The crew immediately attempted to close a valve in a device called the blowout preventer, which sits on the ocean floor over the top of the well borehole. It did not work properly. Overwhelmed separator The crew had the option of diverting the mud and gas away from the rig, venting it safely through pipes over the side. Instead, the flow was diverted to a device on board the rig designed to separate small amounts of gas from a flow of mud. The so-called mud-gas separator was quickly overwhelmed and flammable gas began to engulf the rig. No gas alarm The rig had an onboard gas detection system that should have sounded the alarm and triggered the closure of ventilation fans to prevent the gas reaching potential causes of ignition, such as the rig’s engines. This system failed. No battery for BOP The explosion destroyed the control lines the crew were using to attempt to close safety valves in the blowout preventer. However, the blowout preventer has its own safety mechanism in which two separate systems should have shut the valves automatically when it lost contact with the surface. One system seems to have had a flat battery and the other a defective switch. Consequently, the blowout preventer did not close. “It is evident that a series of complex events, rather than a single mistake or failure, led to the tragedy. Multiple parties, including BP, [oilfield services company] Halliburton and [offshore drilling company] Transocean, were involved,” said Tony Hayward, BP’s chief executive. Topics:
Markdown	Close Advertisement [Skip to content](https://www.newscientist.com/article/dn19425-the-eight-failures-that-caused-the-gulf-oil-spill/#first-link) [Sign in](https://www.newscientist.com/login/ "Sign In page link") Light - [Curiosity engine](https://www.newscientist.com/curiosity-engine) - [Events](https://www.newscientist.com/science-events/) - [Tours](https://www.newscientist.com/tours/) - [Shop](https://shop.newscientist.com/) [Subscribe now](https://subscription.newscientist.com/packages/p/cms/TB) ### Explore by section - [News](https://www.newscientist.com/section/news/) - [Features](https://www.newscientist.com/section/features/) - [Newsletters](https://www.newscientist.com/sign-up/) - [Podcasts](https://www.newscientist.com/podcasts/) - [Video](https://www.newscientist.com/video/) - [Comment](https://www.newscientist.com/section/comment/) - [Culture](https://www.newscientist.com/section/culture/) - [Games](https://www.newscientist.com/games/) - \\| - [This week's magazine](https://www.newscientist.com/issues/current/) ### Explore by subject - [Health](https://www.newscientist.com/subject/health/) - [Space](https://www.newscientist.com/subject/space/) - [Physics](https://www.newscientist.com/subject/physics/) - [Technology](https://www.newscientist.com/subject/technology/) - [Environment](https://www.newscientist.com/subject/environment/) - [Mind](https://www.newscientist.com/subject/mind/) - [Humans](https://www.newscientist.com/subject/humans/) - [Life](https://www.newscientist.com/subject/life/) - [Mathematics](https://www.newscientist.com/subject/mathematics/) - [Chemistry](https://www.newscientist.com/subject/chemistry/) - [Earth](https://www.newscientist.com/subject/earth/) - [Society](https://www.newscientist.com/subject/society/) ### Explore our products and services - [Curiosity engine](https://www.newscientist.com/curiosity-engine) - [Events](https://www.newscientist.com/science-events/) - [Tours](https://www.newscientist.com/tours/) - [Shop](https://shop.newscientist.com/) [Subscribe now](https://subscription.newscientist.com/packages/p/cms/TB) [Subscribe now](https://subscription.newscientist.com/packages/p/cms/TB) #### [Earth](https://www.newscientist.com/subject/earth/) # The eight failures that caused the Gulf oil spill By [Justin Mullins](https://www.newscientist.com/author/justin-mullins/) 8 September 2010 Eight catastrophic failures led to the explosion that destroyed the Deepwater Horizon drilling rig in the Gulf of Mexico, killing 11 people and leading to one of the [biggest oil leaks in history](https://www.newscientist.com/special/deepwater-horizon-oil-spill), according to [BP’s long-awaited investigation into the accident](http://www.bp.com/liveassets/bp_internet/globalbp/globalbp_uk_english/incident_response/STAGING/local_assets/downloads_pdfs/Deepwater_Horizon_Accident_Investigation_Report.pdf). BP accepts its role in the disaster but also points the finger at two of its contractors. The [accident occurred on 20 April](https://www.newscientist.com/article/mg20627595-100-oil-slick-fight-continues-with-robots-and-fire) as the team aboard Deepwater Horizon was preparing to temporarily abandon a well it had drilled some 70 kilometres from the US coast. The day before the accident, the crew had pumped cement to the bottom of the borehole, a standard procedure intended to prevent oil leaking out. On the day of the accident, the team were conducting checks to determine that that the well had been properly sealed. Advertisement BP says the accident was caused by the failure of eight different safety systems that were meant to prevent this kind of incident: ## Dodgy cement The cement at the bottom of the borehole did not create a seal, and oil and gas began to leak through it into the pipe leading to the surface. BP says the cement formulation seems not to have been up to the job. ## Valve failure The bottom of the pipe to the surface was sealed in two ways. It too was filled with cement, and it also contained two mechanical valves designed to stop the flow of oil and gas. All of these failed, allowing oil and gas to travel up the pipe towards the surface. ## Pressure test misinterpreted The crew carried out various pressure tests to determine whether the well was sealed or not. The results of these tests were misinterpreted, so they thought the well was under control. ## Leak not spotted soon enough Whether a well is under control or not, the crew at the surface should be able to detect a flow of oil and gas towards the surface by looking for unexpected increases in pressure in the well. Exactly this kind of increase occurred about 50 minutes before the rig exploded, but it was not interpreted as a leak. ## Valve failure no. 2 About 8 minutes before the explosion, a mixture of mud and gas began pouring onto the floor of the rig. The crew immediately attempted to close a valve in a device called the blowout preventer, which sits on the ocean floor over the top of the well borehole. It did not work properly. ## Overwhelmed separator The crew had the option of diverting the mud and gas away from the rig, venting it safely through pipes over the side. Instead, the flow was diverted to a device on board the rig designed to separate small amounts of gas from a flow of mud. The so-called mud-gas separator was quickly overwhelmed and flammable gas began to engulf the rig. ## No gas alarm The rig had an onboard gas detection system that should have sounded the alarm and triggered the closure of ventilation fans to prevent the gas reaching potential causes of ignition, such as the rig’s engines. This system failed. ## No battery for BOP The explosion destroyed the control lines the crew were using to attempt to close safety valves in the blowout preventer. However, the blowout preventer has its own safety mechanism in which two separate systems should have shut the valves automatically when it lost contact with the surface. One system seems to have had a flat battery and the other a defective switch. Consequently, the blowout preventer did not close. “It is evident that a series of complex events, rather than a single mistake or failure, led to the tragedy. Multiple parties, including BP, \[oilfield services company\] Halliburton and \[offshore drilling company\] Transocean, were involved,” said Tony Hayward, BP’s chief executive. Topics: - [environment](https://www.newscientist.com/article-topic/environment/) / - [Deepwater Horizon](https://www.newscientist.com/article-topic/deepwater-horizon/)/ - [pollution](https://www.newscientist.com/article-topic/pollution/)/ - [oil](https://www.newscientist.com/article-topic/oil/) Advertisement ## Sign up to our weekly newsletter Receive a weekly dose of discovery in your inbox. We'll also keep you up to date with New Scientist events and special offers. 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Readable Markdown	Eight catastrophic failures led to the explosion that destroyed the Deepwater Horizon drilling rig in the Gulf of Mexico, killing 11 people and leading to one of the [biggest oil leaks in history](https://www.newscientist.com/special/deepwater-horizon-oil-spill), according to [BP’s long-awaited investigation into the accident](http://www.bp.com/liveassets/bp_internet/globalbp/globalbp_uk_english/incident_response/STAGING/local_assets/downloads_pdfs/Deepwater_Horizon_Accident_Investigation_Report.pdf). BP accepts its role in the disaster but also points the finger at two of its contractors. The [accident occurred on 20 April](https://www.newscientist.com/article/mg20627595-100-oil-slick-fight-continues-with-robots-and-fire) as the team aboard Deepwater Horizon was preparing to temporarily abandon a well it had drilled some 70 kilometres from the US coast. The day before the accident, the crew had pumped cement to the bottom of the borehole, a standard procedure intended to prevent oil leaking out. On the day of the accident, the team were conducting checks to determine that that the well had been properly sealed. BP says the accident was caused by the failure of eight different safety systems that were meant to prevent this kind of incident: ## Dodgy cement The cement at the bottom of the borehole did not create a seal, and oil and gas began to leak through it into the pipe leading to the surface. BP says the cement formulation seems not to have been up to the job. ## Valve failure The bottom of the pipe to the surface was sealed in two ways. It too was filled with cement, and it also contained two mechanical valves designed to stop the flow of oil and gas. All of these failed, allowing oil and gas to travel up the pipe towards the surface. ## Pressure test misinterpreted The crew carried out various pressure tests to determine whether the well was sealed or not. The results of these tests were misinterpreted, so they thought the well was under control. ## Leak not spotted soon enough Whether a well is under control or not, the crew at the surface should be able to detect a flow of oil and gas towards the surface by looking for unexpected increases in pressure in the well. Exactly this kind of increase occurred about 50 minutes before the rig exploded, but it was not interpreted as a leak. ## Valve failure no. 2 About 8 minutes before the explosion, a mixture of mud and gas began pouring onto the floor of the rig. The crew immediately attempted to close a valve in a device called the blowout preventer, which sits on the ocean floor over the top of the well borehole. It did not work properly. ## Overwhelmed separator The crew had the option of diverting the mud and gas away from the rig, venting it safely through pipes over the side. Instead, the flow was diverted to a device on board the rig designed to separate small amounts of gas from a flow of mud. The so-called mud-gas separator was quickly overwhelmed and flammable gas began to engulf the rig. ## No gas alarm The rig had an onboard gas detection system that should have sounded the alarm and triggered the closure of ventilation fans to prevent the gas reaching potential causes of ignition, such as the rig’s engines. This system failed. ## No battery for BOP The explosion destroyed the control lines the crew were using to attempt to close safety valves in the blowout preventer. However, the blowout preventer has its own safety mechanism in which two separate systems should have shut the valves automatically when it lost contact with the surface. One system seems to have had a flat battery and the other a defective switch. Consequently, the blowout preventer did not close. “It is evident that a series of complex events, rather than a single mistake or failure, led to the tragedy. Multiple parties, including BP, \[oilfield services company\] Halliburton and \[offshore drilling company\] Transocean, were involved,” said Tony Hayward, BP’s chief executive. Topics:
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