2.7 Case Study: Oil Pollution Event

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What Is Oil Pollution?

Oil pollution happens when crude oil or refined oil products are released into the environment — usually into the ocean, a river, or a coastline — where they do not belong. This can happen because of accidents involving oil tankers (large ships that carry oil), explosions on offshore oil rigs (platforms built in the sea to drill for oil), or pipeline leaks.

Oil is a thick, dark liquid, and even a relatively small spill can spread across a huge area of water and cause enormous damage to wildlife and human communities.

Background — What Happened?

• The Deepwater Horizon was an offshore oil drilling rig (a large platform floating in the Gulf of Mexico, off the coast of the southern United States).
• On 20 April 2010, a sudden explosion occurred on the rig caused by a blowout — this means high-pressure oil and gas burst upward uncontrollably from deep underground through the drill pipe.
• The explosion killed 11 workers and injured many others.
• The rig caught fire and sank two days later.
• Because the wellhead (the opening of the oil well on the seabed, about 1,500 metres underwater) could not be sealed quickly, oil gushed freely into the ocean for 87 days before it was finally capped.
• An estimated 4.9 million barrels of crude oil (roughly 780 million litres) spilled into the Gulf of Mexico — making it the largest marine oil spill ever recorded.

Causes of the Spill

Understanding why the spill happened helps us learn how to prevent future ones:

• Equipment failure: A key safety device called the blowout preventer (a large valve designed to seal the well in an emergency) failed to work properly. It did not close off the pipe when the blowout began.
• Human error: Investigations found that workers and company managers made poor decisions about the drilling process, ignoring warning signs that pressure in the well was building dangerously.
• Cost-cutting: The company operating the rig (BP — British Petroleum) was found to have prioritised saving money over following the safest procedures.
• Depth of the well: Because the well was extremely deep underwater, it was very difficult for engineers to reach and repair the problem quickly.