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How Offshore Drilling Works

More Offshore Production Platforms
A spar production platform floats at sunset in the Gulf of Mexico. The structure's massive cylindrical hull extends down into the depths for hundreds of feet.
A spar production platform floats at sunset in the Gulf of Mexico. The structure's massive cylindrical hull extends down into the depths for hundreds of feet.
Getty Images/Handout/Getty Images News/Getty Images

­­In the last section, we looked at some of the varieties of offshore production platforms that allow petroleum companies to reach drill sites as deep as 3,500 feet (1,067 meters). But there's a great deal of oil under the world's oceans, and more than a few methods of reaching it. Some of these designs do away with the traditional concept of an oil platform altogether, while others elevate some of the designs from the last section to even grander proportions.

Floating production system: These platforms can take the form of either floating semisubmersible platforms or drill ships. The basic idea behind their design is that, once the well has been drilled, much of the production equipment can be mounted on the seafloor and the petroleum pumped to the surface facilities through flexible risers. Meanwhile, the platform or ship stays in position with anchors or a dynamic positioning system. This approach allows oil companies to reach depths of up to 6,000 feet (1,829 meters).

Tension leg platform: This platform is essentially a king-sized version of the Sea Star platform, except the tension legs extend from the ocean floor to the platform itself. It experiences more horizontal motion and a certain degree of vertical motion, but it allows oil companies to drill at depths of up to 7,000 feet (2,134 meters), well over a mile (1.6 kilometers) beneath the waves.

Subsea system: This approach takes the idea of mounting the wellhead on the sea floor and applies it to even greater depths -- 7,000 feet (2,1334 meters) or more. Once the well has been drilled by a surface platform, the automated systems transfer the oil and natural gas to production facilities by either risers or undersea pipelines.

­Spar platform: Finally, if you absolutely need to drill a hole at a depth of 10,000 feet (3,048 meters), then the spar platform is the oil rig for you. With this design, the drilling platform sits atop a giant, hollow cylindrical hull. The other end of the cylinder descends around 700 feet (213 meters) into the ocean depths. While the cylinder stops far above the ocean floor, its weight stabilizes the platform. A network of taunt cables and lines trail out from the cylinder to secure it to the ocean floor in what is called a lateral catenary system. The drill string descends down through the length of the cylinder's interior and down to the ocean floor.

As technology improves and existing petroleum reserves wane, exploration will continue to dive into the subterranean depths. This combination of deeper waters and deeper oil wells will pose even greater challenges for oil companies.

While technology plays a vital role in offshore drilling, these massive constructions are also home to large crews of workers. In the next section, we'll take a look at life on an oil rig.