Offshore construction

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Oil platform

Offshore construction is the installation of structures and facilities in a marine environment, usually for the production and transmission of electricity, oil, gas and other resources. It is also called maritime engineering.

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Construction and pre-commissioning is typically performed as much as possible onshore. To optimize the costs and risks of installing large offshore platforms, different construction strategies have been developed. [1]

One strategy is to fully construct the offshore facility onshore, and tow the installation to site floating on its own buoyancy. Bottom founded structure are lowered to the seabed by de-ballasting (see for instance Condeep or Cranefree), whilst floating structures are held in position with substantial mooring systems. [1]

The size of offshore lifts can be reduced by making the construction modular, with each module being constructed onshore and then lifted using a crane vessel into place onto the platform. [1] A number of very large crane vessels were built in the 1970s which allow very large single modules weighing up to 14,000 tonnes to be fabricated and then lifted into place.[ citation needed ]

Specialist floating hotel vessels known as flotels or accommodation rigs are used to accommodate workers during the construction and hook-up phases. This is a high cost activity due to the limited space and access to materials.[ clarification needed ]

Oil platforms are key fixed installations from which drilling and production activity is carried out. Drilling rigs are either floating vessels for deeper water or jack-up designs which are a barge with liftable legs. [2] Both of these types of vessel are constructed in marine yards but are often involved during the construction phase to pre-drill some production wells.

Other key factors in offshore construction are the weather windows which define periods of relatively light weather during which continuous construction or other offshore activity can take place. Safety of personnel is another key construction parameter, an obvious hazard being a fall into the sea from which speedy recovery in cold waters is essential. Environmental issues are also often a major concern, and environmental impact assessment may be required during planning.

The main types of vessels used for pipe laying are the "derrick barge (DB)", the "pipelay barge (LB)" and the "derrick/lay barge (DLB)" combination. Closed diving bells in offshore construction are mainly used for saturation diving in water depths greater than 120 feet (40 m), less than that, the surface oriented divers are transported through the water in a wet bell or diving stage (basket), a suspended platform deployed from a launch and recovery system (LARS, or "A" frame) on the deck of the rig or a diving support vessel. The basket is lowered to the working depth and recovered at a controlled rate for decompression. Closed bells can go to 1,500 feet (460 m), but are normally used at 400 to 800 feet (120 to 240 m).[ citation needed ]

Offshore construction includes foundations engineering, structural design, construction, and/or repair of offshore structures, both commercial and military. [1]

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Related Research Articles

<span class="mw-page-title-main">Oil platform</span> Large offshore structure with oil drilling and related facilities

An oil platform is a large structure with facilities to extract and process petroleum and natural gas that lie in rock formations beneath the seabed. Many oil platforms will also have facilities to accommodate the workers, although it is also common to have a separate accommodation platform bridge linked to the production platform. Most commonly, oil platforms engage in activities on the continental shelf, though they can also be used in lakes, inshore waters, and inland seas. Depending on the circumstances, the platform may be fixed to the ocean floor, consist of an artificial island, or float. In some arrangements the main facility may have storage facilities for the processed oil. Remote subsea wells may also be connected to a platform by flow lines and by umbilical connections. These sub-sea facilities may include of one or more subsea wells or manifold centres for multiple wells.

<span class="mw-page-title-main">Semi-submersible platform</span> Marine vessel used in offshore roles wtth good stability and seakeeping

A semi-submersible platform is a specialised marine vessel used in offshore roles including as offshore drilling rigs, safety vessels, oil production platforms, and heavy lift cranes. They have good ship stability and seakeeping, better than drillships.

<span class="mw-page-title-main">Malaysia Marine and Heavy Engineering</span>

Malaysia Marine and Heavy Engineering Holdings Berhad is a Malaysian owned shipbuilding and heavy engineering industries company. It was formerly known as Malaysia Shipyard and Engineering Sdn Bhd. MHB has been long involved in oil and gas engineering and construction works.

<span class="mw-page-title-main">Drillship</span> Vessel fitted for offshore drilling

A drillship is a merchant vessel designed for use in exploratory offshore drilling of new oil and gas wells or for scientific drilling purposes. In recent years the vessels have been used in deepwater and ultra-deepwater applications, equipped with the latest and most advanced dynamic positioning systems.

<span class="mw-page-title-main">Marine engineering</span> Engineering and design of shipboard systems

Marine engineering is the engineering of boats, ships, submarines, and any other marine vessel. Here it is also taken to include the engineering of other ocean systems and structures – referred to in certain academic and professional circles as “ocean engineering.”

Marine architecture is the design of architectural and engineering structures which support coastal design, near-shore and off-shore or deep-water planning for many projects such as shipyards, ship transport, coastal management or other marine and/or hydroscape activities. These structures include harbors, lighthouses, marinas, oil platforms, offshore drillings, accommodation platforms and offshore wind farms, floating engineering structures and building architectures or civil seascape developments. Floating structures in deep water may use suction caisson for anchoring.

<span class="mw-page-title-main">Offshore drilling</span> Mechanical process where a wellbore is drilled below the seabed

Offshore drilling is a mechanical process where a wellbore is drilled below the seabed. It is typically carried out in order to explore for and subsequently extract petroleum that lies in rock formations beneath the seabed. Most commonly, the term is used to describe drilling activities on the continental shelf, though the term can also be applied to drilling in lakes, inshore waters and inland seas.

Subsea technology involves fully submerged ocean equipment, operations, or applications, especially when some distance offshore, in deep ocean waters, or on the seabed. The term subsea is frequently used in connection with oceanography, marine or ocean engineering, ocean exploration, remotely operated vehicle (ROVs) autonomous underwater vehicles (AUVs), submarine communications or power cables, seafloor mineral mining, oil and gas, and offshore wind power.

"Offshore", when used in relation to hydrocarbons, refers to operations undertaken at, or under the, sea in association with an oil, natural gas or condensate field that is under the seabed, or to activities carried out in relation to such a field. Offshore is part of the upstream sector of the oil and gas industry.

<span class="mw-page-title-main">Jackup rig</span> Type of mobile platform

A jackup rig or a self-elevating unit is a type of mobile platform that consists of a buoyant hull fitted with a number of movable legs, capable of raising its hull over the surface of the sea. The buoyant hull enables transportation of the unit and all attached machinery to a desired location. Once on location the hull is raised to the required elevation above the sea surface supported by the sea bed. The legs of such units may be designed to penetrate the sea bed, may be fitted with enlarged sections or footings, or may be attached to a bottom mat. Generally jackup rigs are not self-propelled and rely on tugs or heavy lift ships for transportation.

Deepwater drilling, or deep well drilling, is the process of creating holes in the Earth's crust using a drilling rig for oil extraction under the deep sea. There are approximately 3400 deepwater wells in the Gulf of Mexico with depths greater than 150 meters.

Offshore concrete structures, or concrete offshore structures, are structures built from reinforced concrete for use in the offshore marine environment. They serve the same purpose as their steel counterparts in oil and gas production and storage. The first concrete oil platform was installed in the North Sea in the Ekofisk oil field in 1973 by Phillips Petroleum, and they have become a significant part of the marine construction industry. Since then at least 47 major concrete offshore structures have been built.

<span class="mw-page-title-main">Grup Servicii Petroliere</span>

Grup Servicii Petroliere is a Romanian company providing offshore integrated services for oil and gas industry. The company, established in 2004, is a member of UPETROM Group.

<span class="mw-page-title-main">Pipe-laying ship</span> Ship type used to lay subsea pipelines

A pipelaying ship is a maritime vessel used in the construction of subsea infrastructure. It serves to connect oil production platforms with refineries on shore. To accomplish this goal a typical pipelaying vessel carries a heavy lift crane, used to install pumps and valves, and equipment to lay pipe between subsea structures.

<span class="mw-page-title-main">Suction caisson</span> Open bottomed tube anchor embedded and released by pressure differential

Suction caissons are a form of fixed platform anchor in the form of an open bottomed tube embedded in the sediment and sealed at the top while in use so that lifting forces generate a pressure differential that holds the caisson down. They have a number of advantages over conventional offshore foundations, mainly being quicker to install than deep foundation piles and being easier to remove during decommissioning. Suction caissons are now used extensively worldwide for anchoring large offshore installations, like oil platforms, offshore drillings and accommodation platforms to the seafloor at great depths. In recent years, suction caissons have also seen usage for offshore wind turbines in shallower waters.

<span class="mw-page-title-main">Offshore geotechnical engineering</span> Sub-field of engineering concerned with human-made structures in the sea

Offshore geotechnical engineering is a sub-field of geotechnical engineering. It is concerned with foundation design, construction, maintenance and decommissioning for human-made structures in the sea. Oil platforms, artificial islands and submarine pipelines are examples of such structures. The seabed has to be able to withstand the weight of these structures and the applied loads. Geohazards must also be taken into account. The need for offshore developments stems from a gradual depletion of hydrocarbon reserves onshore or near the coastlines, as new fields are being developed at greater distances offshore and in deeper water, with a corresponding adaptation of the offshore site investigations. Today, there are more than 7,000 offshore platforms operating at a water depth up to and exceeding 2000 m. A typical field development extends over tens of square kilometers, and may comprise several fixed structures, infield flowlines with an export pipeline either to the shoreline or connected to a regional trunkline.

<span class="mw-page-title-main">Submarine pipeline</span> Pipeline that is laid on the seabed or below it inside a trench

A submarine pipeline is a pipeline that is laid on the seabed or below it inside a trench. In some cases, the pipeline is mostly on-land but in places it crosses water expanses, such as small seas, straits and rivers. Submarine pipelines are used primarily to carry oil or gas, but transportation of water is also important. A distinction is sometimes made between a flowline and a pipeline. The former is an intrafield pipeline, in the sense that it is used to connect subsea wellheads, manifolds and the platform within a particular development field. The latter, sometimes referred to as an export pipeline, is used to bring the resource to shore. Sizeable pipeline construction projects need to take into account many factors, such as the offshore ecology, geohazards and environmental loading – they are often undertaken by multidisciplinary, international teams.

<span class="mw-page-title-main">Subsea production system</span> Wells located on the seabed

Subsea production systems are typical wells located on the seabed, shallow or deep water. Generally termed as Floating production system, where the petroleum is extracted at the seabed and the same can be tied back to an already existing production platform or an onshore facility. The oil platform well is drilled by a movable rig and the extracted oil or natural gas is transported by submarine pipeline under the sea and then to rise to a processing facility. It is classified into

Ocean development refers to the establishing of human activities at sea and use of the ocean, as well as its governance.

References

  1. 1 2 3 4 5 6 7 8 9 10 11 12 Gerwick, Ben C. Jr (2007). Construction of Marine and Offshore Structures (third ed.). Taylor and Francis. ISBN   978-0-8493-3052-0.
  2. Bevan, John, ed. (2005). The Professional Divers's Handbook (second ed.). Alverstoke, GOSPORT, Hampshire: Submex Ltd. ISBN   978-0950824260.
  3. Sadeghi, Kabir (2007). "An Overview of Design, Analysis, Construction and Installation of Offshore Petroleum Platforms Suitable to Cypress/Oil Gas Fields". J. Soc. & Appl. Sci. 2 (4): 1–16.
  4. Sadeghi, Kabir (2008). "Significant Guidance for Design and Construction of Marine and Offshore structures". J. Soc. & Appl. Sci. 4 (7): 67–92.