Was the Deepwater Horizon Incident Really Unprecedented?

Deepwater Horizon

Published May 5, 2020 7:58 PM by Thibaut Eude

Ten years ago, the accident of the Deepwater Horizon drilling platform occurred, killing 11 oil workers and resulting in the largest oil spill in US history (3,190,000 bbl). Eighty-seven days was needed for the largest peacetime response organization to regain control over an ultra-deep offshore oil well gone wild.

Some have compared this accident with two other cases that have caused marine oil spills: the blowout of the Ixtoc I drilling platform and the grounding of the Exxon Valdez supertanker.

I believe that these two comparisons are irrelevant, and even if we can observe some similarities on the surface, the Deepwater Horizon case remains unprecedented.

The Ixtoc 1 drilling platform oil spill (1979)

Ixtoc I was a drilling platform operated on behalf of PEMEX, the Mexican national operator, in the Bay of Campêche, off Mexico. In 1979, this platform also suffered a blowout and generated extensive marine pollution (although it was never officially registered), which WHOI estimated at 2,914,592 bbl. (approx. 477,000 m3).

The Ixtoc I wellhead was only about 50 meters deep compared to the 1,500 meters of the well drilled by Deepwater Horizon. At this depth, there is no natural light, no human access, and this requires a fully instrumented and remotely operated working environment. The well descends to a geological depth of approximately 4,000 meters and it is one of the so-called High Pressure High Temperature (HPHT) wells with a high Gas on Oil Ratio (GOR) which makes it a reactive well.

Taken back to the technology of each respective epoch, the well drilled by Deepwater Horizon was a challenge of a magnitude far greater than that the one drilled by Ixtoc I.

The grounding of the Very Large Crude Carrier (VLCC) Exxon Valdez (1989)

"At four minutes past midnight, on 24 March [1989], the vessel went hard aground. The Exxon Valdez, loaded with 1,264,155 barrels of North Slope crude oil [approx. 200,985 m³], had grounded on the hard rock reef below [Bligh Reef in Alaska’s pristine Prince William Sound], opening eight of its eleven tanks."

The oil spill was estimated between 41,639 m3 and 121,133 m3.

The Exxon Valdez case has been very often cited, because it is the origin of a profound reform of the American legislation on pollution at sea, the Oil Pollution Act, which has been in force in the United States since 1990. This is also the only known case of major marine pollution in US waters.

"The Exxon Valdez oil spill has entered American cultural consciousness as an iconic cataclysm. In journalistic accounts of the Deepwater Horizon blowout, the Exxon Valdez was used repeatedly as a bench mark against which to measure the scope of the Gulf of Mexico tragedy."

In fact, the whole pollution response system has been sized accordingly and has never been reviewed since.

However, the Exxon Valdez was a vessel with a finite quantity of oil in its tanks, which makes it possible to estimate the maximum quantities that could be released and therefore to adjust pollution response accordingly. Predicting and measuring the "production" from a blow-out well is much more complicated. The quantity is virtually unlimited, in the sense that it may be out of all proportion to what an existing tanker can carry. Finally, the spill is localized at the bottom of the sea, bringing an additional dimension to the diffusion of the oil into the environment.

"Experience and response methods applicable to other oil spills [including the Exxon Valdez] have often proved either impossible or ineffective."

Admiral Thad Allen, then National Incident Commander (NIC), wrote in his report: "The Deepwater Horizon oil spill is the largest and most complex our nation has ever confronted, more analogous to the challenges posed by Apollo 13 than the Exxon Valdez spill of 1989."


There was therefore an unprecedented discrepancy between the ability to produce oil and the ability to treat pollution.

The state of the art of pollution response engineers has remained essentially the same since the grounding of the Exxon Valdez, while the state of the art of drilling engineers has shifted in scale.

Existent oil pollution response capacities (means, methods, organizations) have been overwhelmed. It was the innovative, original solutions designed and developed during the crisis that made it possible to contain the leak and finally shut the well.

"The U.S. Geological Survey estimated that approximately 17 percent of the oil that emanated from the blowout was recovered by devices that were designed, fabricated, and installed in the riser or on the blowout preventer after the release began. This was by far the most successful spill response method." 

The Deepwater Horizon disaster was unprecedented.

Thibaut Eude is a PhD holder from the engineering school Mines Paristech in France. His PhD thesis focused on the Deepwater Horizon accident.


1 https://www.epa.gov/sites/production/files/2015-01/documents/phase2ruling.pdf 
2 https://www.arlis.org/docs/vol1/B/31206602/31206602v1.pdf 
3 https://academic.oup.com/jah/article/99/1/219/854785 
4 https://www.pnas.org/content/109/50/20212 
5 https://biotech.law.lsu.edu/climate/docs/BPDWH.pdf 

The opinions expressed herein are the author's and not necessarily those of The Maritime Executive.