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August 10, 2018updated 31 Jan 2020 7:49am

The five biggest oil spills offshore: lessons to learn

There’s no getting around it, oil spills are costly, destructive and potentially deadly to offshore workers and the local marine environment. But, what lessons can the offshore oil industry learn from such disasters?

By Talal Husseini

API Energy’s Oil Spill Prevention and Response guidelines give three primary objectives to deal with the resulting fallout: prevent the spill from reaching shore, reduce the impact on marine life, and speed the degradation of any unrecovered oil. With this in mind, Offshore Technology takes a look at the five biggest oil spills worldwide and the key reasons behind them to uncover what lessons can be learned to prevent repeating mistakes of the past.

Biggest oil spills 1: 260 million gallons

Gulf War – Persian Gulf – 19 January 1991

The biggest oil spill on the list was technically not an accident. During the first Gulf War, Iraqi troops retreating from Kuwait opened the valves of several offshore oil wells and pipelines to slow down the approaching US Army. The aftermath resulted in one of the biggest oil spills in world history, with around 260 million gallons of crude oil flowing into the Persian Gulf, according to government sources. The 4in-thick oil slick spread across an area the size of Hawaii.

According to UNESCO’s Intergovernmental Oceanographic Commission, the spill resulted in little permanent damage to local fisheries and coral ecosystems.

Lesson: expect the unexpected

Abdul Nabi Al-Ghadban of Kuwait Institute for Scientific Research said: “If you have an offshore operation, you need to have a good contingency plan in case of spillage, damage, earthquake, or a problem with the pipeline.

“We learned the lesson that we have to have an action plan – you have to expect the unexpected.”

Biggest oil spills 2: 210 million gallons

Deepwater Horizon – Mexican Gulf – 20 April to 15 July 2010

The largest accidental oil spill was recorded in the Gulf of Mexico in 2010. On 20 April, an explosion at the Deepwater Horizon offshore drilling rig caused oil to gush from the sea-floor 5,000ft below. The blast itself killed 11 workers on the platform and injured 17 others. The leak was finally brought under control three months later by capping the wellhead, but only after it had released around 210 million gallons into the sea.

The oil spill caused extensive damage to marine ecosystems and severely disrupted the Gulf’s fishing and tourism industries. In an attempt to protect US coasts, authorities used skimmer ships, floating containment booms, anchored barriers and sandbags along the shoreline.

Lesson: procedural complacency can kill

Investigations later revealed that the cement pumped in to seal BP’s Macondo Well a day before the explosion was not given enough time to set properly, and that two safety defences subsequently failed. A witness report by oil-field cementing expert Glen Benge said: “The BP engineers chose to accept additional risks when designing the cement job with the awareness that remedial cementing work could be done at a later date.”

Biggest oil spills 3: 140 million gallons

Ixtoc-1 – Mexican Gulf – 3 June 1979 to 23 March 1980

Another accidental spill located in the Gulf of Mexico, this time a Pemex operated oil well in the Bay of Campeche, collapsed after building pressure underwater caused an explosion on 3 June 1979. This triggered the release of 140 million gallons of crude into the Mexican Gulf over a ten-month period, and the resulting slick measured around 1,100 square miles, an area a bit larger than Luxemburg.

Mud, steel, iron and lead balls were dropped down Ixtoc-1’s shaft in order to block the flow of oil. While the methods slowed the leakage, Pemex was unable to stop the oil until two relief wells were drilled nearby.

Lesson: tropical environments seem more resilient, but the true damage may be hidden

A report from Frontiers in Marine Science found two revealing facts in the aftermath of Ixtoc-1. It said: “Given their rich biodiversity, tropical systems are more resilient and perhaps can recover faster from a disturbance than a temperate system.” However, this was not a wholly positive statement.

It went onto say: “In regions such as Campeche Sound, with a high input of biogenic hydrocarbons from estuarine systems, the detection of petrogenic hydrocarbons in sediments or animal tissues can have a masking effect.”

The biological diversity in a tropical ecosystem could impede the ability to measure the real long-term destruction of the marine environment, making it much more difficult to clean up the spills.

While it may not assist prevention, knowledge of the local marine environment is crucial when undertaking clean-ups to mitigate disasters.

Biggest oil spills 4: 90 million gallons

Atlantic Empress – Caribbean Sea – 19 July 1979

A bad year for the biggest oil spills. In July 1979, two fully loaded Greek supertankers, Atlantic Empress and Aegean Captain, collided with each other in the Caribbean Sea off the Trinidadian coast. Together, both vessels leaked 90 million gallons of crude and caught fire. The Atlantic Empress exploded around 300 nautical miles offshore and 26 crew members were killed. On 3 August 1979, the Empress sunk, leaving a behind a fiery slick of oil and not much else.

In the fallout of the collision, no impact study was conducted on the level of pollution exhibited. Follow-up reports found the Empress was more than 100 degrees off course and neither vessel provided adequate lookouts or could successfully reduce their speed. Coverage of the disaster was ultimately eclipsed by the Ixtoc-1 explosion.

Lesson: navigation technology is useful when properly manned

Four days after the collision, Trinidad and Tobago deputy commissioner of customs Victor Cockburn explained that supertankers as big as the Empress and the Captain need six miles between them to turn safely.

While advancements in ship navigation technology have helped to reduce the number of large-scale collisions since the Atlantic Empress, accidents still occur.

Many tankers these days are fitted with the latest radar and navigation systems, including GPS tracking, automatic identifications systems, and radio communications. Royal United Services Institute director of military sciences Peter Roberts says: “Provided you are keeping a radar watch and a visual lookout, then collisions are avoidable.”

Roberts added that he had travelled on ships where in some instances there is no-one manning the bridge, adding: “An alarm is going off on the radar and they’re reliant on that alarm waking whoever is on watch.”

Over-reliance on technology may be a zeitgeist in 2018, but if no-one is interpreting and relaying the emergency then another disaster as large as the Atlantic Empress spill could happen.

Biggest oil spills 5:  80 million gallons

ABT Summer – Offshore Angola – 28 May 1991

The South Korean-built Liberian oil tanker ABT Summer exploded off the coast of Angola while heading to Rotterdam in the Netherlands. A blast onboard caused the ship to catch fire and the entire payload spilled into the South Atlantic Ocean. The blast was said to be caused by a corroded ballast tank. The tanker burned for three days before sinking and the oil slick spread across 80 square miles.

Thanks to the incident’s offshore location, the clean-up was mitigated by the high seas, which broke up the oil slick at little cost to the marine environment.

Lesson: keep up-to-date with new marine safety standards

Despite the smaller impact due to the fortunate position of the disaster, several maritime incidents have been caused by the corrosion of ballast tanks, prompting the need for more stringent regulations. The Performance Standard for Ballast Tank Coatings (PSPC) came into effect in 2008, specifying how protective coatings should be applied during vessel construction and requiring a re-coating every 15 years.

The Ballast Water Management Convention was enacted in 2017. It aimed to avoid the presence of invasive species in ballast tanks while also mitigating corrosion, finding new water treatment systems that kill species without damaging tanks. Double-hull tankers have since become the standard, with shipbuilders investing more funds in coatings. Single-hull tankers, such as ABT Summer, have generally been phased out.   

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