Offshore Asset Construction

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Offshore wind turbines

Offshore wind turbines are installed individually and in groups, called wind farms. Wind turbine systems comprise a tower, hub and blades (the rotor), and nacelle (houses the generator. They are typically attached to a reinforced concrete foundation. Based on the wind characteristics of the site, these structures are generally designed to conform to the International Electrotechnical Commission (IEC) 61400-1 wind turbine design class.

800

Unknown

The platform construction class is not known.

801

Caisson

Caisson platforms use large diameter caissons to support a single well completion with a minimal deck. The deck is capable of supporting limited production, control equipment, and navigational aids. Caisson platform completions are limited to water depths of 100 feet or less.

802

Compliant Tower

Compliant Towers consist of narrow, flexible towers and piled foundations that can support a conventional deck for drilling and production operations. Unlike fixed platforms, Compliant Towers withstand large lateral forces by sustaining significant lateral deflections and are usually used in water depths between 1,000 and 2,000 feet.

803

Fixed Jacket Platform

Fixed platforms consist of jackets (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. Fixed platforms are economically feasible for installation in water depths up to 1,500 feet.

804

Jackup

Jackups are platforms that can be jacked up above the sea using legs that can be lowered like jacks. These platforms, used in relatively low depths, are designed to move from place to place and then anchor themselves by deploying the jack-like legs.

805

Mini Tension Leg Platform

Mini Tension Leg Platforms (MTLP) are floating platforms of relatively low cost developed for production of smaller deepwater reserves that would be uneconomic to produce using more conventional deepwater production systems. They can also be used as a utility, satellite, or early production platform for larger deepwater discoveries.

806

Drill Rig

Drill rig

807

Semi-Submersible Floating Production System

Semi-submersible floating production platforms have legs of sufficient buoyancy to cause the structure to float, but weight sufficient to keep the structure upright. These rigs can be moved from place to place and ballasted up or down by altering the amount of flooding in buoyancy tanks. They are generally anchored by cable anchors during drilling operations, though they can also be kept in place by the use of dynamic positioning. Semi-submersibles can be used in depths from 200 to 6,000 feet.

808

Drill Ship

Drill ships are maritime vessels that have been fitted with drilling apparatuses. They are most often used for exploratory drilling of new oil or gas wells in deep water, but can also be used for scientific drilling. They are often built on modified tanker hulls and outfitted with dynamic positioning systems to maintain their position over a well. Drill ships are able to drill in water depths of over 6,500 feet.

809

SPAR Floating Production System

SPARs consist of a large diameter single vertical cylinder supporting a deck. They have typical fixed platform topsides (surface decks with drilling and production equipment), three types of risers (production, drilling, and export), and hulls moored with taut caternary systems of six to 20 lines anchored into the seafloor. SPARs are generally used in water depths up to 3,000 feet.

810

Submersible Production System

Floating vessels, usually used as mobile offshore drilling units (MODUs), that are supported primarily on large pontoon-like structures submerged below the sea surface. The operating decks are elevated 100 or more feet above the pontoons on large steel columns. Once on the desired location, this type of structure is slowly flooded until it rests on the sea floor. After the well is completed, the water is pumped out of the buoyancy tanks, and the vessel is refloated and towed to the next location. Submersibles operate in relatively shallow water, since they must rest on the seafloor.

811

Underwater Production Units, Completion Units, and Templates

Subsea Systems range from single subsea wells producing to a nearby platform, FPS, or TLP to multiple wells producing through a manifold and pipeline system to a distant production facility. These systems are presently used in water depths greater than 5,000 feet.

812

Tension Leg Platform

Tension Leg Platforms (TLPs) consist of a floating structure held in place by vertical, tensioned tendons connected to the sea floor by pile-secured templates. Tensioned tendons provide for the use of a TLP in a broad water depth range with limited vertical motion. Larger TLPs have been successfully deployed in water depths approaching 4,000 feet.

813

Well Protector

Well head protection structures