1. Trouble in the Gulf Deepwater Horizon
An ultra-deepwater semi-submersible offshore oil drilling rig built in 2001 in South Korea.

2. Deepwater Horizon was a semi-submersible oil rig.
Different platforms are used depending on the depth of the water at the drill site.
Deepwater Horizon was a semi-submersible oil rig.
Different platforms are used depending on the depth of the water.

3. A semi-submersible platform is partially filled with water for stability.

4. The picture on the left shows the maximum water depth for each platform type. The yellow color is the seafloor. Deepwater Horizon had drilled to about 13,000 feet below the seafloor.

5. Zooming in…
Deepwater Horizon was located in the Gulf of Mexico.

6. Gulf of Mexico: The light blue is shallow water near land
Gulf of Mexico: The light blue is shallow water near land. The darker blue is deeper water.

7. Deepwater Horizon Wellhead
Deepwater Horizon was doing exploratory drilling in water 5,000 feet deep. It is approximately 41 miles off the Louisiana coast.

8. Digital Terrain Image
NOAA's Office of Coast Survey constructed this digital terrain model of the sea floor in the vicinity of the Deepwater Horizon oil rig using multibeam survey data collected during the 1990s. The hydrographic data and model can help experts better understand ocean circulation.

9. What happened?

10. A different rig would be used to pump the oil they had found.
Exploratory work had been completed and the well was being prepped for Deepwater Horizon to move to another location.
A different rig would be used to pump the oil they had found.
The reservoir was estimated to contain
15 billion gallons of oil.

11. Step-by-Step
The following slides will show a cross section of the drilling pipe. The illustration is NOT to scale. Different colors represent the thick drilling fluid known as “mud,” the cement used to temporarily shutdown the well, and the gas that made its way to the surface.

12. Heavy drilling fluid, “mud,” was used during exploratory drilling operations to keep any natural gas from rising up the pipe.
The picture on the left shows the entire rig and pipe. The picture on the right is a zoom in on the area where the pipe enters the seafloor.
The investigation continues, but based on what is known experts have worked out the most likely scenario. This diagram of the well’s lining is vastly foreshortened to emphasize the well’s layers.
Engineers constructed the well out of telescoping segments of metal casing that became narrower as the reached deeper below the surface.
Natural gas was locked in a high-pressure reservoir, trying to get to the surface.
Heavy drilling fluid (known as mud) kept the gas from rising.
Source: Transocean testimony and Wall Street Journal research

13. As they prepared to leave the site, cement was pumped into the well to seal it until the next rig came to remove the oil.
Because the cement is heavier than the mud, it sinks to the bottom of the well.
3. Workers pumped cement to seal off the sides of the well.
BP didn’t test the cement to see if it was solid.
Oil and gas may have gotten into the inside of the casing
Any gas rising up the side of the well would have expanded, pushing against both the inner pipe within the well and a seal at the top.
Due to the design of the well, the gas had a straight shot to the top of the well.

14. This is commonly known as a “blowout.”
As one of the final steps to prep the pipe, the heavy mud was removed and replaced with much lighter seawater.
The gas easily moved through the seawater and up the pipe to the surface where it caught fire.
This is commonly known as a “blowout.”
Blowouts rarely happen.
Gas somehow got into the pipe.
Workers DID NOT set a final cement plug before removing the heavy mud. This cement plug would have stopped gas from in the well from reaching the surface.
The heavy mud was the only thing keeping the gas from coming to the surface.
On April 20, workers began removing the mud and replacing it with seawater allowing gas to shoot to the surface where it caught fire.

15. Both of the emergency devices meant to prevent such an accident failed:
Blowout preventer
Sheer rams
The 2 emergency devices which were meant to prevent an accident like the one that occurred both failed.
Source: Congressional testimony from BP

16. On Tuesday, April 20, 2010 an explosion rocked the oil drilling platform.
On Tuesday, April 20, 2010 an explosion rocked the oil drilling platform, sending a column of fire into the sky and touching off a frantic search at sea for at least 11 originally reported missing (now presumed killed in the initial explosion). Seventeen people were hurt. There were 126 workers on the rig at the time of the explosion.

17. Coast Guard vessels try to extinguish the fire on DEEPWATER HORIZON.
Photo Courtesy: Dan McDonald - This picture is believed to have been taken by a nearby Chevron worker

19. After burning for 36 hours, the rig sank on April 22, 2010

20. The oil rig is now resting on the seafloor 5,000 feet deep and about ¼ mile northwest of the well.
Drawing is not to scale

21. They were unsuccessful.
Oil flows into the Gulf
Remotely operated vehicles (ROVs) were used to attempt to close the blowout preventer valve which would have stopped the oil flow.
They were unsuccessful.

22. Another attempt to stop the flow
The initial collar and cap didn’t work because of the force of the oil flowing from the blowout preventer.
Source: BP
In this drawing you get a sense of the size of the blowout preventer.
A man is standing on the left for scale.

23. After a number of attempts, on July 15, a 75-ton cap stopped the oil flow
A tightly fitting cap with 3 valves was placed over the well. Each valve was slowly closed, allowing the cap to stem the flow without being blown off by the pressure. This is a temporary fix until the well can be permanently plugged with mud and cement.

24. An estimated 184 million gallons of oil flowed into the Gulf before they were able to cap the well.
On September 19, 2010, after a weekend of pouring cement into the base of the ruptured well in the Gulf of Mexico, pressure tests conducted confirmed the permanent seal was holding and the well was permanently capped.
(left pix)
(right pix)

25. Notice how the plug will be set far below the sea floor and wellhead.
Heavy drilling fluid (mud) and cement will permanently cap the well. This is commonly known as “bottom kill.”
Notice how the plug will be set far below the sea floor and wellhead.

26. Update…
Along with the oil that reached the surface, an underwater plume had also formed after the spill. While much of oil at the surface is not longer visible, the spill formed a underwater plume still persists. Even at lower concentrations, this plume can have devastating effects such as being toxic to the creatures living there, coating organisms, and forming dead zones.

27. This image shows the actual data gathered.
This map shows the underwater plume that the oil has formed. The oil is in black (the outline of which is an approximation based on the data collected).
The blue line represents the path of the unmanned submarine which was taking the samples. Notice how it zig-zagged across the oil plume. The rainbow colored portion (red, yellow, aqua) visually represent the amount of distinguishing petroleum hydrocarbons found. The researchers detected a class of petroleum hydrocarbons at concentrations of more than 50 micrograms per liter. The water samples collected at these depths had no odor of oil and were clear. “The plume was not a river of Hershey’s Syrup,” said Reddy (Christopher Reddy, a WHOI marine geochemist and oil spill expert ). “But that’s not to say it isn’t harmful to the environment.”
For the scale: Blue indicates low methane concentrations, red high. So places where the scale is aqua, yellow or red indicated the presence of oil in the water.
Pix: