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Oil Extraction from Sea Floor - Different Types of Offshore Production Platforms.

written by: Raunekk • edited by: Lamar Stonecypher • updated: 3/31/2009

If during the exploratory drills the companies feel that they have struck gold then plans to setup offshore production platforms are made. In this article we will learn about the different types of production platforms that companies use for drilling out oil.

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    Introduction

    Once the process of exploring oil is completed and the site for drilling is decided, companies start planning for installing platforms that would stay there for decades. The drilling sites are generally ones that face extremely rough weather conditions and for this reason it is required that the platforms are firmly installed at their sites. The choice of a platform depends on a number of factors. The platform selected should be such that it is worth the massive investment and expenses. Let's have a look at the different types of offshore production platforms that a company can choose from.

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    Fixed platform.

    This platforms are meant for deep sea drilling. The platform is formed of concrete and steel. Tons of material is required in constructing this type of platform.They can operate at a depth of 1500 or less. This type of platforms are extremely stable due to their weights. It is hard to imagine that these structures are not fixed to the sea surface, they stay stable at the drilling site just due to their concrete weight.The whole oil rig rests on the concrete slab.

    platform-fixed1 

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    Compliant tower

    They are almost similar to fixed platforms. The only difference is that the amount of concrete that is used in constructing the platform is much less, this is done by making the structure narrower. It is made to drill at a depths of 1500-3000 feet. The stability is far lesser than the fixed platforms. They get easily affected by rough weather and winds.

    platform-compliant-tower1 

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    Sea star platform

    Sea star platfroms are almost same like semisubmersible platforms. The oil rig rests on hollow barges that can be filled with water and then lowered in the water. Just as in semisubmersible platforms, in sea star platforms the hollow barges are filled upto the operating height. Then instead of anchors, tension legs are lowered in the water. These tension legs are tubes that fixes firmly to the sea surface allowing a bit of movement to absorb jerks due to rough weather and winds. They are made to operate at depth of 500-3500 feet.

    sea star 

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    Floating production system

    Through this system, companies can drill even at a depth of 6,000 feet. In this type of system, the drilling apparatus is fixed to the surface of the sea bed. The oil that is drilled is sent to the platform through tubes know as risers. The platform is kept stationary with the help of anchors or dynamically positioning system.

    floating production platform 

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    Tension leg platform

    Tension leg platform is similar to sea star platform. But unlike in sea star, the tension legs dont go all the way to the sea floor. Due to this the platform experiences more horizontal motion due to the jerks from the rough weather. This platform allows drilling at an amazing depth of 7000 feet.

    tension leg platform 

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    Subsea system.

    This platform has features from all the platforms that we discussed earlier. It is used to drill at depths of 7000 and above. The drilling apparatus is fixed on the sea bed and the drilled oil is sent up with the help of risers.

    -subsea-system 

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    Lateral catenary system

    In the catenary system, the drilling apparatus is in the shape of a cylinder. Unlike other systems, the risers are lowered to the sea floor from inside the cylinder apparatus. The platform is extremely firm and can withstand rough climate. It is also used for depths of 7000 feet.

    catenary system 

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    References

    How offshore drilling works by Robert Lamb

    Image Credits

    http://www.globalsecurity.org/military/systems/ship/images/platform-fixed1.jpg

    http://www.globalsecurity.org/military/systems/ship/images/platform-compliant-tower1.jpg

    http://www.atlantia.com/seastar/images/scenarios_drytree.jpg

    http://www.offshore-technology.com/features/feature_images/feature1412/5-subsea-system.jpg

    http://www.globalsecurity.org/military/systems/ship/images/spars-image2.jpg

    http://www.offshore-technology.com/projects/thunderhawke/images/1-thunder-hawk.jpg

    http://www.globalsecurity.org/military/systems/ship/images/platform-tension-leg1.jpg

    http://www.offshore-technology.com/projects/balder/images/balder3.jpg