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The energy industry has a long history of using spar platforms to operate in the sea. The oil and gas industry uses spars to drill for oil and gas in the ocean safely. The wind energy industry also uses this technology to install offshore wind turbines.
There are many different types of spar platforms. Each has its benefits and disadvantages, as well as various design characteristics. This article will discuss the purpose of spar platforms subjected to ocean waves and modern platform classifications that have evolved throughout the years.
A spar is a floating platform primarily utilized in intense waters. It is named after logs used as buoys in shipping and moored vertically. Engineers developed spar buoy foundations as an alternative to traditional floating platforms. Deep draft spars are less affected by wind, waves, and currents, enabling dry tree and subsea production.
History and Evolution
Spars have been effective platforms for riser support, processing, and drilling, with exceptional performance and dependability. Today, these offshore structures cover three generations of spar technology traditional, truss, and cell spars. Spars encompass both dry-tree and wet-tree applications, with and without platform rigs. In addition, ocean engineering has improved to develop new technologies over the past years.
1976
The Brent Spar was the first spar production platform constructed to store and offload crude oil products. In June 1976, Shell installed it at the Brent Oilfield.
1990
By the 1990s, Greenpeace was outraged by the platform’s attempted deep-sea disposal. Shell disassembled the spar and built a quay in Norway with the remains.
1996
Kerr McGee installed the Neptune spar in the Gulf of Mexico in September 1996, the first intended for production (now Anadarko).
2010
Perdido, a truss spar in the Gulf of Mexico, has the world’s deepest production platform, with a mean water depth of 2,438 meters. Shell operates Perdido.
Spar Platform as an Offshore Structure
Offshore structures include:
- Pipelines
- Fixed and floating platforms
- Floating production storage and offloading facilities (FPSOs)
- Pipeline end manifolds
- Pipeline end terminals
- Countless other significant constructions
Some of these structures or pieces are buried in the sea floor. Others are in the seawater or splash zone, submerged and exposed above the water level at others.
A series of deck support rooms for oil and gas separation, drilling rigs, production facilities, and crew housing is on the surface. These structures are on steel legs directly anchored to the seabed. These platforms are immobile and intended for long-term use.
Steel jacket, concrete caisson, and floating steel are three types of structures for specific functions and purposes. Steel jackets are vertical pieces of tubular steel members deposited into the seabed. These elements are frequently utilized as flotation chambers in floating structures to stabilize the system.
Components of Spar Platform Design
SPARs are primarily intended to be:
- A standard one-piece cylindrical hull
- A truss SPAR, with truss elements linking the buoyant upper hull (called a hard tank) to the soft bottom tank with permanent ballast
- A SPAR cell made out of numerous vertical cylinders
Hard Tank
Top tensioned risers are installed in a center well that runs the entire length of the hard tank. Instead of hydraulic tensioners used on TLPs, buoyancy cans support the risers, which provide top riser tension. The buoyancy cans have guides that act as lateral restraints.
Midsection Tank
The SPAR trusses are X-braced similarly to offshore jacket X-bracing, and they serve as a stiff structure between the hard tank above and the keel tank below. Heave plates are frequently installed on trusses to attenuate heave reaction.
Soft Tank
In classic spars, fixed ballast is added to the soft tank at the bottom of the hull, followed by variable ballast added to the hard tank at the top. The soft tank may use water or hematite as a fixed ballast. Finally, the structure’s keel provides buoyancy and is flooded to upend the hull.
Vertical Cylinder
The Spar Platform consists of a single large-diameter vertical cylinder that supports a deck. It has a standard FP topside (surface deck with drilling and production equipment), three different risers (production, drilling, and export), and a hull secured with a taut catenary system of 6–20 lines anchored into the sea floor.
Spar Platform Types
Classic Spar
A traditional spar comprises a tall, cylindrical hull with tanks for substantial ballast positioned at the bottom of the cylinder.
Truss Spar
In motion control systems, Truss Spar platforms differ from semisubmersible platforms and TLPs. One of the Truss structure’s distinguishing features is that its center of gravity is constantly lower than the center of buoyancy, ensuring a positive GM. As a result, the Truss Spar is unconditionally stable. In addition, because the Truss Spar’s mooring method provides no stability, it does not list or capsize even when removed from its mooring.
Cell Spar
Red Hawk Cell Spar platforms made history by being commissioned as the first of their kind. It was hailed as the first cell spar ever made, and it is still the only cell spar ever created just over a decade later.
Like the existing spars, the system is unconditionally stable since the center of buoyancy is above the center of gravity. The upper portion of the Cell Spar comprises six outside cells surrounding a central cell. These higher cells provide the buoyancy needed to keep the vessel afloat. Three outer cells are extended down to the keel to create the lowest portion of the spar. Fixed ballast is included within the lower amount of these legs to assure the structure’s stability.
Mounting Structures of Spar Platforms
MMS is a floating platform that supports all necessary components that keep them floating. The floating platform is moored to prevent displacement due to changes in water level.
Pure-floats Design
The modular system may be combined with pins or bolts to build a big platform. It employs a specially constructed float that can directly handle PV panels. In addition, each system’s unit has primary and secondary floats. The auxiliary float’s primary function is to provide a walkway for maintenance and additional buoyancy.
Pontoon Design With Metal Structures
Another frequent design employed by some project developers uses a metal framework similar to a land-based system with pontoons to give buoyancy, removing the need for specifically built floats.
Anchoring And Mooring System
A floating platform’s mooring system is often attached with nylon polyester or nautical nylon ropes linked to bank bollards and lashed at each corner. Different mooring techniques include anchoring to a nearby bank, the bottom of a lake, reservoir, or pilings erected on the subsoil of a water body.
Design
The standard floating structure holds PV arrays, inverters, combiner boxes, lightning arresters, and other components on a floating bed constructed of fiber-reinforced plastic (FRP), high-density polyethylene (HDPE), or metal constructions. Anchoring and mooring systems help to buoy the entire floating bed. Operators should perform initial site assessments of the planned waterbody to determine the feasibility of the site for the development of the FSPV project.
Spar Structures Conversion To Wave and Wind Energy
There are numerous floating platform solutions for offshore wind turbines, such as spar buoys, tension leg platforms (TLPs), barges, and hybrid models.
Among the floating wind turbine concepts offered, spar-types such as catenary moored spar (CMS) and tension leg spar (TLS) wind turbines appear to be well-suited to the extreme environmental conditions in the North Sea.
Catenary Moored Spar (CMS)
A catenary-moored spar wind turbine (CMS) platform with moored spars supports a wind turbine. The wind turbine includes the tower, nacelle, and rotor. Because we are dealing with an aero-servo-hydro-elastic multi-body system, the dynamic behavior of the integrated structure is complex. The stiff and elastic modes can be excited by wind and wave motions caused by time- and geometry-dependent loading.
Tension Leg Spar (TLS)
A Tension Leg Spar (TLS) wind turbine is a spar platform with pre-tensioned mooring lines that support a wind turbine. This line is a tubular element with a diameter of 1.0m. Due to additional nonlinearities from tension leg effects, the dynamic behavior of the TLS may be more complicated than that of the CMS. Wind and wave motions can trigger stiff and elastic modes via time- and geometry-dependent loading. Because of the tension leg, the emotions are strongly connected.
Bigger, Better Floating Platforms
Investment in conventional platform systems increases as they become more critical in complex deep-water operations. Expanding the capabilities of technology for floating systems, from FPSOs to semisubmersible platforms, is a vital industry priority.
Atlantis
Another of BP’s fields pushing the limits of floating technology is Atlantis. The semisubmersible platform can accommodate 18 wells and is the deepest moored one, operating in nearly 7,000 feet of water. The water depths and reservoir structure make Atlantis one of BP’s most technologically complex developments.
Shell’s Perdido
This project will use a new method to cluster several wells on the seafloor and connect them to a spar platform – the world’s deepest spar production platform. In terms of spar design, light deck load platforms are a significant priority for the future.
Conclusion
Spar platform design, manufacturing, and installation are not limited to offshore oil and gas. Spar platforms benefit from wind power production, water desalination, wave energy converters, and other marine renewable energy sources.
Spar platforms, floating offshore constructions, have grown in popularity over the years due to their unique characteristics, making them suited for various functions and applications in the ocean environment.
Their investment increases as floating production systems become more significant in complex deep-water operations. We may expect more unique buildings to be developed at sea as research on this technology continues.