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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
Dynamic positioning (DP) is a computer-controlled system to automatically maintain a vessel's position and heading by using its own propellers and thrusters. Position reference sensors, combined with wind sensors, motion sensors and gyrocompass ...
systems.
History
The first drillship was the ''
CUSS I
Project Mohole was an attempt in the early 1960s to drill through the Earth's crust to obtain samples of the Mohorovičić discontinuity, or Moho, the boundary between the Earth's crust and mantle. The project was intended to provide an e ...
'', designed by Robert F. Bauer of Global Marine in 1955. The ''CUSS I'' had drilled in 400-foot-deep waters by 1957.
[Schempf, F. (2007). Pioneering Offshore: The Early Years. ulsa, OK PennWell Custom Pub..]
Robert F. Bauer became the first president of Global Marine in 1958.
In 1961 Global Marine started a new drillship era. They ordered several self-propelled drillships each with a rated centerline drilling of 20,000 foot-wells in water depths of 600 feet. The first was named ''CUSS (
Glomar) II'', a 5,500-deadweight-ton vessel, costing around $4.5 million. Built by a Gulf Coast shipyard, the vessel was almost twice the size of the ''CUSS I'', and became the world's first drillship built as a new construction which set sail in 1962.
In 1962, The Offshore Company elected to build a new type of drillship, larger than that of the ''Glomar'' class. This new drillship would feature a first-ever anchor mooring array based on a unique turret system. The vessel was named ''Discoverer I''. The ''Discoverer I'' had no main propulsion engines,
meaning it needed to be towed out to the drill site.
Application
A drillship can be used as a platform to carry out well maintenance or completion work such as casing and tubing installation, subsea tree installations, and well capping. Drillships are often built to the design specifications set by the oil production company and/or investors.
From the first drillship ''CUSS I'' to the ''Deepwater Asgard'', the fleet size has been growing ever since. In 2013 the worldwide fleet of drillships topped 80 ships, more than double its size in 2009. Drillships are not only growing in size but also in capability, with new technology assisting operations from academic research to ice-breaker class drilling vessels. U.S. President
Barack Obama
Barack Hussein Obama II ( ; born August 4, 1961) is an American politician who served as the 44th president of the United States from 2009 to 2017. A member of the Democratic Party, Obama was the first African-American president of the U ...
's decision in late March 2010 to expand U.S. domestic exploratory drilling seemed likely to increase further developments of drillship technology.
Design
![Mohopix-1](https://upload.wikimedia.org/wikipedia/commons/2/2b/Mohopix-1.gif)
Drillships are just one way to perform various types of drilling. This function can also be performed by
semi-submersibles
Semi-submersible may refer to a self-propelled vessel, such as:
* Heavy-lift ship, which partially submerge to allow their cargo (another ship) to float into place for transport
* Narco-submarine, some of which remained partially on the surface
* ...
, jackups,
barges
Barge nowadays generally refers to a flat-bottomed boat, flat-bottomed inland waterway vessel which does not have its own means of mechanical propulsion. The first modern barges were pulled by tugs, but nowadays most are pushed by Pusher (boat) ...
, or platform rigs.
Drillships have the functional ability of semi-submersible drilling rigs and also have a few unique features that separate them from all others, first being the ship-shaped design. A drillship has greater mobility and can move quickly under its own propulsion from drill site to drill site in contrast to semi-submersibles and jackup barges and platforms. Drillships have the ability to save time sailing between oilfields worldwide. A drillship takes 20 days to move from the Gulf of Mexico to offshore Angola, whereas a semi-submersible drilling unit must be towed and takes 70 days.
[Leffler, W., Sterling, G., & Pattarozzi, R. (2011). Deepwater Petroleum Exploration & Production: A Nontechnical Guide. Tulsa, Okla.: PennWell Corp.] Drillship construction costs are much higher than that of a semi-submersible. Although mobility comes at a high price, the drillship owners can charge higher day rates and get the benefit of lower idle times between assignments.
The table below depicts the industry's way of classifying drill sites into different vintages, depending on their age and water depth.
The drilling operations are very detailed and in-depth. A simple way to understand what a drillship does to drill, is that a marine riser is lowered from the drillship to the seabed with a blowout preventer (BOP) at the bottom that connects to the wellhead. The BOP is used to quickly disconnect the riser from the wellhead in times of emergency or in any needed situation. Underneath the derrick is a moonpool, an opening through the hull covered by the rig floor. Some of the modern drillships have larger derricks that allow dual activity operations, for example, simultaneous drilling and casing handling.
Types
There are different types of
offshore drilling
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 te ...
units such as the
oil platform
An oil platform (or oil rig, offshore platform, oil production platform, and similar terms) is a large structure with facilities to extract and process petroleum and natural gas that lie in rock formations beneath the seabed. Many oil platfor ...
,
jackup rig
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 a ...
,
submersible drilling rig,
semi-submersible
Semi-submersible may refer to a self-propelled vessel, such as:
* Heavy-lift ship, which partially submerge to allow their cargo (another ship) to float into place for transport
*Narco-submarine, some of which remained partially on the surface
* ...
platform and of course drillships.
All drillships have what is called a ”moon pool”. The
moon pool
A moon pool is a feature of marine drilling platforms, drillships and diving support vessels, some marine research and underwater exploration or research vessels, and underwater habitats, in which it is also known as a wet porch. It is an o ...
is an opening on the base of the hull and depending on the mission the vessel is on, drilling equipment, small submersible crafts and divers may pass through the moon pool. Since the drillship is also a vessel, it can easily relocate to any desired location. Due to their mobility, drillships are not as stable compared to semi-submersible platforms. To maintain its position, drillships may utilize their anchors or use the ship's computer-controlled system on board to run off its
dynamic positioning
Dynamic positioning (DP) is a computer-controlled system to automatically maintain a vessel's position and heading by using its own propellers and thrusters. Position reference sensors, combined with wind sensors, motion sensors and gyrocompass ...
.
[SOS-HOTLO. (n.d.). Off shore drilling. off shore drilling. Retrieved 4 April 2014, from ]
''Chikyū''
One of the world's best-known drillships is Japan's ocean-going drilling vessel ''
Chikyū
is a Japanese scientific drilling ship built for the Integrated Ocean Drilling Program (IODP). The vessel is designed to ultimately drill beneath the seabed, where the Earth's crust is much thinner, and into the Earth's mantle, deeper than a ...
'', which actually is a research vessel. The ''Chikyū'' has the remarkable ability to drill to a depth of below the seabed, bringing that to two to four times that of any other drillship.
[Pacella, R. (1 April 2010). How It Works: The Deepest Drill. '']Popular Science
''Popular Science'' (also known as ''PopSci'') is an American digital magazine carrying popular science content, which refers to articles for the general reader on science and technology subjects. ''Popular Science'' has won over 58 awards, incl ...
''. Retrieved 4 April 2014, from http://www.popsci.com/technology/article/2010-03/deepest-drill
''Dhirubhai Deepwater KG1''
In 2011 the
Transocean
Transocean Ltd. is an American company. It is the world's largest offshore drilling contractor based on revenue and is based in Vernier, Switzerland. The company has offices in 20 countries, including Canada, the United States, Norway, Unite ...
drillship ''Dhirubhai Deepwater KG1'' set the world water-depth record at 10,194 feet of water (3,107 meters) while working for
Reliance – LWD and
directional drilling
Directional drilling (or slant drilling) is the practice of drilling non-vertical bores. It can be broken down into four main groups: oilfield directional drilling, utility installation directional drilling, directional boring (horizontal dire ...
done by Sperry Drilling in India.
[Transocean Ltd. Transocean Historical Timeline. Retrieved from http://www.deepwater.com/Prebuilt/timeline/ ]
Drillship operators
*
Diamond Offshore Drilling
Diamond Offshore Drilling, Inc. is an offshore drilling contractor. The company is headquartered in Katy, Texas, United States, and has major offices in Australia, Brazil, Mexico, Scotland, Singapore, and Norway.
The company operates 15 drilling ...
*
International Ocean Discovery Program
The International Ocean Discovery Program (IODP) is an international marine research collaboration dedicated to advancing scientific understanding of the Earth through drilling, coring, and monitoring the subseafloor. The research enabled by IODP ...
*
Noble Corporation
Noble Corporation plc is an offshore drilling contractor organized in London, United Kingdom. Its affiliate, Noble Corporation, is organized in the Cayman Islands. It is the corporate successor of Noble Drilling Corporation.
The company operate ...
*
Seadrill
Seadrill is a deepwater drilling contractor for the petroleum industry. It is incorporated in Bermuda for tax purposes and managed from London and Houston The company operates semi-submersible platforms, jackup rigs and drillships.
History
Seadr ...
*
Transocean
Transocean Ltd. is an American company. It is the world's largest offshore drilling contractor based on revenue and is based in Vernier, Switzerland. The company has offices in 20 countries, including Canada, the United States, Norway, Unite ...
*
Türkiye Petrolleri Anonim Ortaklığı
Türkiye Petrolleri Anonim Ortaklığı (TPAO) (Turkish Petroleum Corporation) was founded in 1954 by Law No. 6327 with the responsibility of being involved in hydrocarbon exploration, drilling, production, refinery and marketing activities of ...
(TPAO)
*
Valaris plc
Valaris plc is an offshore drilling contractor headquartered in Houston, Texas, and incorporated in the UK. It is the largest offshore drilling and well drilling company in the world, and owns 56 rigs, including 40 offshore jackup rigs, 11 dril ...
References
{{ModernMerchantShipTypes
Ship
A ship is a large watercraft that travels the world's oceans and other sufficiently deep waterways, carrying cargo or passengers, or in support of specialized missions, such as defense, research, and fishing. Ships are generally distinguished ...
Offshore engineering