The production facilities sit atop a large submersible hull on a tower. When the lower hull fills with water, it sinks to a lower depth, providing stability while keeping the facilities high and dry. However, instead of giant anchors holding it in place, the Sea Star is connected to the ocean floor by tension legs. These long, hollow tubes remain rigid at all times, preventing any up-and-down motion on the platform.
The legs are just flexible enough to allow side-to-side motion, which helps absorb the stress of waves and wind.
These platforms operate from depths of to 3, feet to 1, meters and are typically used to tap smaller reservoirs in deep waters. 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, feet 1, 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, feet 2, meters , well over a mile 1.
Subsea system : This approach takes the idea of mounting the wellhead on the sea floor and applies it to even greater depths -- 7, feet 2, 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.
With this design, the drilling platform sits atop a giant, hollow cylindrical hull. The other end of the cylinder descends around feet meters into the ocean depths. While the cylinder stops far above the ocean floor, its weight stabilizes the platform. A network of taut 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. Deep-sea waters reach nearly freezing temperatures, contain pressures great enough to crack iron casings and are subject to rough, deep-sea currents. Engineers have to design equipment that can stand up to the pressure, while also preventing boiling oil from hot, underground depths from cooling to a solid form and rupturing pipes when it emerges into the chilly ocean environment.
While antifreeze has played an important part in preventing this thus far, more advanced methods are under development [source: Wired ]. Offshore production platforms may be marvels of modern engineering, but none of that valuable petroleum makes its way out of the wells and into refineries without a great deal of human labor.
In fact, larger oil rigs often employ more than a hundred workers to keep the platform running. As many of these rigs are located far from cities and shores, the employees who range from engineers and geologists to divers and doctors live for weeks at a time on these huge structures. There are definitely pros and cons to working on an offshore platform.
On the plus side, salary and benefits are usually pretty good, and employees typically enjoy long rest periods when they're not at sea. Employees will work one or two weeks on the oil rig, then spend one or two weeks at home. The downside, however, is that when they're at sea, they work hour days, seven days a week. The weeks away from home can strain workers' home lives, as they spend half the year away from their family.
To help cope with these issues, petroleum companies frequently put a great deal of effort into providing comfortable living conditions for offshore workers. In many cases, quarters are on par with those found on major cruise ships -- featuring private rooms, satellite TV and even gym, sauna and recreation facilities. The food onboard also tends to be above average -- and available 24 hours a day. After all, work on an oil rig continues day and night, with employees working rotating schedules of daytime and nighttime shifts.
Helicopters and ships bring in most of the necessary materials for day-to-day life on an oil rig, often through choppy weather conditions. Oil rigs aren't all Jacuzzis and cafeterias, though.
Outside the living quarters, life on an oil rig is a constant encounter with potentially deadly conditions. The business of an oil rig boils down to drawing extremely flammable fluids out of the Earth, burning some of it off in a giant jet of flame and separating highly poisonous hydrogen sulfide gas from the extracted petroleum. On top of this, workers have to deal with all the typical dangers associated with operating dangerous machinery and working at tall heights in windy, stormy conditions.
These measures not only help to safeguard the lives of their employees, but also protect their truly massive financial investment in constructing and sustaining an offshore production platform. Sign up for our Newsletter! Mobile Newsletter banner close. Mobile Newsletter chat close. Mobile Newsletter chat dots. Mobile Newsletter chat avatar.
Mobile Newsletter chat subscribe. Environmental Science. Energy Production. How Offshore Drilling Works. In this part of the world, waves frequently reach as high as 6 feet 2 meters. See more pictures of oil fields and drilling. Hunting for Fossil Fuels " ". Petroleum rises naturally to the surface at this tar seep in central California.
Drilling Rights. Exploratory Drilling " ". Drill ships like this one are often used to drill exploratory wells into suspected petroleum deposits.
Note the drill pipe segments stored on deck. Undersea Drilling " ". An enormous offshore platform lights up the night off the coast of Norway. Striking Oil " ". Offshore drilling platforms burn off excess natural gas, giving them their signature flares.
A Slippery Subject. Mobile Drilling Platforms " ". A jack-up rig can raise and lower itself on three or four massive "legs. Offshore Production Platforms " ". 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.
Hellish Heat and Chilling Depths. Oil Rigs: Cities on the Sea " ". A remote access technician dangles underneath a North Atlantic oil rig to inspect the structure's underbelly. Why is offshore drilling so controversial? What's oil shale? Have we reached peak oil? How do you clean up an oil spill? Coile, Zachery. June 17, April 12, Hale, Briony. June 18, March 12, May 27, In the search for oil and natural gas under the ocean, three general types of drilling rigs are used. A semi-submersible is the most common type of offshore drilling rig, used for drilling in waters more than feet 90 meters deep.
Semi-submersibles are floating vessels supported on large pontoon-like structures submerged below the sea surface. Semisubmersibles are attached to the ocean floor using strong chains or wire cables. Farther offshore, specially designed rigs mounted on ships can drill a well in waters over 10, feet meters deep. These rigs float and can be attached to the ocean bottom using traditional mooring and anchoring systems or they maintain their position by using thrusters to counteract winds, waves and currents.
Each drilling systems is designed to withstand the wide range of wind and wave forces, including severe winter storms and hurricanes. Following is a description of 7 most common types of platforms. A Fixed Platform FP consists of a jacket a tall vertical section made of tubular steel members supported by piles driven into the seabed with a deck placed on top, providing space for crew quarters, a drilling rig, and production facilities.
The fixed platform is economically feasible for installation in water depths up to 1, feet meters. A Compliant Tower CT consists of a narrow, flexible tower and a piled foundation that can support a conventional deck for drilling and production operations. It should be noted at this stage that these legs are fabricated as single units and are fitted with Strand Jacks and cables for installation.
They are not joined by lattice arrangement as per conventional steel jacket supports, but are fixed to the topsides by clamps. The topsides are loaded out of the fabrication shop onto supports on the transport barge and secured. The legs are lifted vertically by crane and clamped to the topsides brackets one by one, the suction piles suspended over the barge hull. Here the legs are lowered to the sea bed, the suction pumps attached by pressure hoses using ROV.
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