The Engineering and Construction of Offshore Oil Platforms

It's estimated that 84% of all Earth's natural resources are located under our oceans. How do we get it out?
Trevor English

The world uses roughly 100 million barrels of oil each and every day in 2019. That's a significant amount of fuel that has to be pumped from underground, processed, and delivered to fueling stations across the world. This significant intake of non-renewable resources also means that oil companies are constantly looking for new oil reserves to tap into to meet the high demand.

In the arctic circle alone, it's estimated that 13% of the entire world's oil reserves are trapped under the ocean floor. In terms of what's under the entire world's oceans, it's estimated that 84% of all non-renewable fuels the earth has is found under the ocean floor. That poses a significant problem, just how do you get all that carbon-based fuel out?

Through offshore drilling and oil platforms.

The development of offshore oil platforms

The first offshore oil platform was constructed in 1897 off of the coast of California. Oil companies invested heavily in the technology over the next several decades.

By 1928, a Texan company placed a mobile offshore oil platform in the wetlands bordering Texas and Louisiana. The structure was essentially just a barge with an oil drill mounted to the top, but it signaled just what might be possible in the industry with more and more innovation.

By 1947, a group of oil companies built the first platform not visible from land in the Gulf of Mexico. 


These first offshore rigs are dwarfed by the offshore rigs of today. Some rigs now have underwater towers that extend to lengths of 4,000 feet or 1200 meters into the ocean. For reference, the Burj Khalifa, the world's tallest building, is just 2,722 feet tall.

In fact, the largest structure mankind has ever moved is a massive oil rig.

How did the oil get underwater?

Any person with the knowledge of how oil is formed, through the compression of carbon-based life-forms over time, might be wondering how the vast amount of the world's oil got trapped under the oceans. The answer is fairly simple.

Roughly 10 to 600 million years ago, all this oil started as plankton and over time, the plankton was compacted through the buildup of sand and mud. 

How do oil companies find oil?

In order to find where all of this oil is located under the seafloor, companies have to use "sniffer equipment." This equipment takes in samples of seawater and determines if there are trace amounts of oil or natural gas.

When they signal they have found something, researchers then have to do a magnetic survey on the seafloor to determine where there might be anomalies underground.

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These survey research teams can also use seismic surveying, which sends shock waves through the seafloor and listens for how those waves are returned through hydrophones.

Once a reserve of oil has been determined, the information is passed off to the respective oil company, and offshore drilling can begin.


Installing an offshore oil platform

The first step after an underwater oil reserve has been found is the installation of exploratory wells. Each of these wells takes 2 to 3 months to install, and they're used to take samples of the rock layers underneath the seafloor. This is the same geological process used for building large buildings on land, except that the process has to be done thousands of feet underwater.

The Engineering and Construction of Offshore Oil Platforms
1 & 2) conventional fixed platforms; 3) compliant tower; 4, 5) vertically moored tension leg and mini-tension leg platform; 6) spar; 7 & 8) semi-submersibles; 9) floating production, storage, and offloading facility; 10) sub-sea completion and tie-back to host facility Source: Wikimedia/Public Domain

Once the core samples taken from the exploratory wells yield more accurate survey results, companies will map out the subsurface structure and determine the exact place to drill the production well. 

Production wells are the main source of any given offshore oil platform, and they're what these platforms are put in place to run. Once the exact location of the production well is determined, engineers start developing plans of how to place the offshore oil well atop it.


One thing you might not be aware of is that these oil wells and platforms don't just drill straight down. Thanks to directional drilling technology, oil platforms have the capability of tapping into tens of different reserves in the same general location. Directional drills have the ability to turn and weave through the underground surface, essentially allowing them to bore to the exact location where oil is located.

The entire process of installing an offshore oil rig takes roughly 2 to 3 years. The average price for one of these rigs is roughly $650 million too, so companies are hedging significant bets on any given location when they choose to install a rig. That said, the aforementioned underground mapping gives enough information that these companies can be fairly certain their investment will pay off over time.

If you're looking to watch an entire documentary on the process, the following video gives an in-depth look.

Operating the well

Offshore oil wells dive deep into the earth's crust, several miles in most cases. Oil platforms will have drilling equipment that allows them to keep drilling wells deeper and deeper or further and further out. 

The drill itself is made up of roughly 10-meter sections that all fit together. So, as the length of these sections is drilled, oil workers just install another section and keep drilling. Again, this process is similar to how oil drilling is carried out on land, rather offshore platforms have the added challenge of being miles out to sea.

Between the oil rig and the floor where the actual drilling is occurring, there's a flexible tube that holds the rotating drill. This tube is called a marine riser, which protects the drill from the elements and breakage while in the ocean.

Once the drill reaches the oil, the process can get a little bit more dangerous. Oftentimes, sub-sea oil reserves can be highly pressurized, which means that oftentimes drilling a hole in them can be much like popping a balloon. This can cause a massive explosion of crude oil on the surface of the rig if not protected against. Oil companies have installed blowout prevention systems that essentially function as specialized valves that only operate when a blowout is detected.

The Engineering and Construction of Offshore Oil Platforms
 Subsea well containment operations. Source: Wikimedia/Public Domain

Once the oil (or natural gas) is tapped into, the offshore rig can function as the initial processing and management of the oil or natural gas collection process. 

Day to day life on an offshore oil rig

As you can imagine, oil rig workers are completely isolated from the rest of the world, meaning that these rigs have to have everything needed not only for oil production but also for the daily life of the workers. If a rig is close enough to shore, workers might be transported on ships or helicopters for their shifts, but for rigs further out to sea, it makes more sense for there to be accommodations on the rig for the workers to live.

The living quarters for rigs are typically built as far away from the hazards of oil production as possible and as close as possible to the escape boats. This is to ensure that if something were to go wrong with the offshore rig, human loss is as minimized as possible.

While the manning needs of an oil platform varies drastically based on its size, platforms in generall will have about 100-150 workers onboard to keep everything running smoothly. 

Offshore rigs run 24 hours, 365 days a year, which means that everyone on a rig works in day/night shifts.

Being that this job requires the workers to be away from their families and loved ones for extended periods of time, they are compensated fairly well. Entry-level positions are roughly $50,000 per year, whereas more specialized engineering positions can earn upwards of $200,000 per year. Another thing to note is that all of your living expenses are taken care of while on the rig, so your expenses are drastically lower on rigs where you are out to sea for extended periods of time.

To see a little bit more about the daily life on an oil rig, take a look at the video below.


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