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 gyrocompas ...

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 ear ...

'', 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 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 was the 44th president of the United States from 2009 to 2017. A member of the Democratic Party, he was the first African American president in American history. O ...

's decision in late March 2010 to expand U.S. domestic exploratory drilling seemed likely to increase further developments of drillship technology.

Design

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 *S ...

, jackups,

barges A barge is typically a flat-bottomed vessel which does not have its own means of mechanical propulsion. Original use was on inland waterways, while modern use is on both inland and marine water environments. The first modern barges were pull ...

, 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 ter ...

units such as the

oil platform An oil platform (also called an oil rig, offshore platform, oil production platform, etc.) 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 w ...

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 ...

, 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 *S ...

platform and of course drillships. All drillships have what is called a ”moon pool”. The

moon pool A moon pool is an equipment deployment and retrieval feature used by oil platforms, marine drilling platforms, drillships, diving support vessels, fishing vessels, oceanography, marine research and underwater exploration or research vessels, and ...

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

.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 an ...

'', 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 called pop-science or popsci) is an interpretation of science intended for a general audience. While science journalism focuses on recent scientific developments, popular science is more broad ranging. It may be written ...

''. 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 drilling company. It is the world's largest offshore drilling contractor based on revenue and is based in Steinhausen, Switzerland. The company has offices in 20 countries, including Canada, the United States, ...

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 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. It operates 15 drilling rigs incl ...

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, England. Its affiliate, Noble Corporation, is organized in the Cayman Islands. It is the corporate successor of Noble Drilling Corporation. The company operates 24 dr ...

Odfjell Drilling Odfjell Drilling Ltd. is an oil drilling, well service, and engineering company. Current operations The company has 3 divisions: * Mobile Offshore Drilling - Owns 6 drillships and operates in Norway, United Kingdom, Angola, Vietnam, and Brazil. ...

Seadrill Seadrill is an offshore drilling contractor providing worldwide offshore drilling services to the oil and gas industry. Its primary business is the ownership and operation of drillships, semi-submersible rigs, and jack-up rigs for operations in ...

Türkiye Petrolleri Anonim Ortaklığı TPAO or Turkish Petroleum Corporation has been established in order to perform hydrocarbon exploration, drilling, production, refinery and marketing activities on behalf of the Turkish Republic with the law 6327 in 1954. Many milestones in Turki ...

(TPAO) * Valaris Limited * Foresea

References

{{ModernMerchantShipTypes

Ship A ship is a large watercraft, vessel that travels the world's oceans and other Waterway, navigable waterways, carrying cargo or passengers, or in support of specialized missions, such as defense, research and fishing. Ships are generally disti ...

Offshore engineering