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  • Lim Shen Huan

Blood in the water: Deepwater Horizon from a chemical engineering perspective

Edited by Amelia Gross.

At 9:41 pm on the 20th of April 2010, the lights blew out on the Deepwater Horizon oil rig. Roars of mechanical thumping and the eerie beeping of the combustible gas sensors spread throughout the darkness and echoed into the deep blue abyss of the Gulf of Mexico surrounding the rig. Sudden jolts of pressure shook the ground as horrified and panicked workers stumbled through the dark, attempting desperately to seal the well. Some cried, many prayed. And then the lights came back on (fig.1).

(Fig. 1) Fireball of the Deepwater Horizon oil rig- National Geographic 2021 (Accessed: 15 June)

Instantly, the oil rig was engulfed in a massive explosion resulting in an intense fireball scorching the night sky. Accompanied with a deafening boom- heavy chunks of metal debris rained from the sky, destroying many parts of the rig instantaneously and crushing several workers. The deadly heat burned several others to death, leaving 11 Deepwater Horizon workers to perish in the initial explosion and the subsequent firestorm.

In the aftermath of the Deepwater Horizon chemical disaster, the sinking of the rig unleashed an ecological catastrophe. The oil well's exposure to ocean currents led to the largest marine oil spill in history with an estimated 210,000,000 US gallons of oil being discharged into the sea. This spillage caused the killing and destruction of entire marine wildlife ecosystems within the Gulf of Mexico and effectively extinguished fishing and tourism industries that relied on the Gulf to make a living (fig. 2). But even with all these terrible consequences, the worst result of the disaster was the pain and heartache dealt upon by the deceased's families who, up until this day, continue to fight for safer off-shore drilling regulations within the oil industry.

(Fig. 2) A boat cuts through an immense layer of oil covering the entire surface of the Gulf of Mexico- Sean Gardner/ Reuters File (Accessed: 15 June)

However, the Deepwater Horizon chemical disaster was entirely preventable. In order to understand how we can prevent the chemical disaster from happening, we first have to learn how offshore drilling is carried out in industry. In order to extract diesel oil from gas reservoirs deep below the seafloor, semi-submersible oil rigs like the Deepwater Horizon (fig. 4) use a long tube (called the riser) with a drill at the end. This drill is used to create a wellbore (fig. 3) beneath the sea floor to reach the natural gas and oil reserves.

(Fig. 3) (Left) Diagram of a wellbore- US Chemical Safety and Hazard Investigation Board (CSB) (Accessed: 15 June)

(Fig. 4) (Right) Diagram of semi-submersible oil rig platform- Shanghai China Petroleum Instrument Co. (Accessed: 15 June)

Occasionally, when the pressure of the drilled rock is higher than the hydrostatic pressure within the riser, oil and gas are forced out of the wellbore and into the pipe. This unplanned entry of oil up the tubing is called a kick in the chemical industry and is extremely dangerous as enough kicks can lead to a blowout- a large, uncontrollable, and powerful release of pressurised oil and gas up the riser and into the oil rig. Blowouts occur at random and are very deadly as the gases collected are highly flammable and, because the collection is sudden and unplanned by the oil rig workers, the gases can quickly find an ignition source leading to an explosion killing many on the oil rig surface. The Deepwater Horizon disaster is a prime example of a catastrophic blowout.

In order to prevent these kicks, risers have drilling mud (fig. 6) flowing in between the oil and the piping to maintain a high enough hydrostatic pressure within the pipe, successfully preventing the necessary pressure differential for a kick (Fig. 5).

(Fig. 5) (Left) Diagram of hydrostatic pressure from the drill mud working against the formation pressure from the drilled rocks- Christina Apostolidou (Accessed: 15 June)

(Fig. 6) (Right) Diagram showing cross section of riser- US Chemical Safety and Hazard Investigation Board (CSB) (Accessed: 15 June)

If, for some reason, the mud fails to maintain a constant pressure, the last line of defence to protect the drill crew at the oil rig is a device called a blowout preventer which is directly connected to the riser at the seabed. The blowout preventer (fig. 7), or BOP, is a complex hydraulically and electrically powered device that’s sole purpose is to block oil and gas from moving up the riser in the event of a kick or blowout. To accomplish this, the crew can manually control the BOP to close pipe rams (fig. 8) and use annular preventers (circular rubber corks) (fig. 9) to physically seal the pipe- fully preventing the flow of oil. If the pipe rams or annular preventers fail to work, the BOP is also equipped with a blind shear ram (a pair of sharp blades) to forcefully cut the pipe and seal the well (fig. 10).

(Fig. 7) (Left) Image of a blowout preventer- US Chemical Safety and Hazard Investigation Board (CSB) (Accessed: 15 June)

(Fig. 8) (Top Right) Diagram showing how a pipe ram closes the riser- US Chemical Safety and Hazard Investigation Board (CSB) (Accessed: 15 June)

(Fig. 9) (Bottom Right) Diagram showing how an annular preventer closes the riser- US Chemical Safety and Hazard Investigation Board (CSB) (Accessed: 15 June)

(Fig. 10) Diagram showing the cutting mechanism of a blind shear ram- Dejan Brkić (Accessed: 15 June)

If all of these safety measures were perfectly working the night of the Deepwater Horizon chemical disaster, the catastrophe would never have happened. But unfortunately, everything that could’ve gone wrong went wrong that night.

Firstly, at the time of the disaster, BP (the company that owned and operated the Deepwater Horizon oil rig), was carrying out a major sealing process of the oil well as they didn’t want to extract any more oil from it. In order to seal the well, they had to install three giant concrete plugs in the column to prevent any oil and gas from leaking. However, BP decided to remove the drilling mud from the riser to increase speed and cut costs. This choice was reckless and dangerous as it now led to the riser lacking the necessary hydraulic pressure to counteract the force from the surrounding rock near the oil well. This, in turn, led to a catastrophic blowout due to the significant difference in pressure.

Furthermore, as the high-pressured oil and gas travelled up the riser in the blowout, the pipe ram, annular preventer, and BOP should’ve prevented the catastrophe from occurring by blocking the oil’s path, but unfortunately they didn’t. At the time of the incident, the annular preventer was damaged and the BOP malfunctioned due to lack of maintenance. Instead of cutting off the pipe completely and sealing it, the BOP instead only bent the pipe slightly- still allowing the oil to flow.

(Fig. 11) Diagram of BOP malfunction- The Times Picayune (Accessed: 15 June)

As for the annular preventer, BP already knew it was broken, as a few weeks prior a worker had moved the shaft while the annular was being used and thus, ripped it to shreds. BP did not replace the annular or fix the BOP due to the fact that the oil well was being sealed soon and they did not want to incur any additional costs to the rig shut down. Additionally, the piperams, too, were useless to prevent the disaster as they couldn’t be controlled properly due to an issue with the control panels not working.

From the evidence gathered, we now know the multitude of ways chemical engineering could’ve prevented the Deepwater Horizon chemical disaster. This catastrophe serves as a stark reminder of the gravity of negligence and the lack of responsibility can lead to deadly outcomes and destructive pathways. In the end- BP had created the worst man-made environmental disaster in the history of the United States, resulting in the loss of life of 11 innocent workers and the destruction of countless wildlife habitats. Hopefully the future can look back on this disaster and learn what not to do when running an oil rig.

(Fig. 12) Image of the Deepwater Horizon Oil Spill from space- National Aeronautics and Space Association (NASA) (Accessed: 15 June)



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