A drillship is a maritime vessel that has been fitted with drilling apparatus. It is most often used for exploratory offshore drilling
Offshore drilling refers to a mechanical process where a wellbore is drilled through the seabed. It is typically carried out in order to explore for and subsequently produce hydrocarbons which lie in rock formations beneath the seabed...
of new oil or gas wells in deep water or for scientific drilling
Scientific drilling is a way to probe down into the Earth, allowing scientists and students to obtain samples of sediments, crust, and upper mantle. In addition to rock samples, drilling technology allows humans to obtain samples of connate fluids and of the subsurface biosphere, mostly microbial...
. The drillship can also be used as a platform to carry out well maintenance or completion work such as casing and tubing installation or subsea tree installations. It is often built to the design specification of the oil production company and/or investors, but can also be a modified tanker
A tanker is a ship designed to transport liquids in bulk. Major types of tankship include the oil tanker, the chemical tanker, and the liquefied natural gas carrier.-Background:...
hull outfitted with a dynamic positioning
Dynamic positioning is a computer controlled system to automatically maintain a vessel's position and heading by using its own propellers and thrusters...
system to maintain its position over the well.
The greatest advantages these modern drillships have is their ability to drill in water depths of more than 2500 meters and the time saved sailing between oilfields worldwide. Drillships are completely independent, in contrast to semi-submersible
A semi-submersible is a specialised marine vessel with good stability and seakeeping characteristics. The semi-submersible vessel design is commonly used in a number of specific offshore roles such as for offshore drilling rigs, safety vessels, oil production platforms and heavy lift cranes.The...
s and jackup barges.
In order to drill, a marine riser is lowered from the drillship to the seabed with a blowout preventer
A blowout preventer is a large, specialized valve used to seal, control and monitor oil and gas wells. Blowout preventers were developed to cope with extreme erratic pressures and uncontrolled flow emanating from a well reservoir during drilling. Kicks can lead to a potentially catastrophic...
(BOP) at the bottom that connects to the wellhead.
Drillships are just one way to perform exploratory drilling. This function can also be performed by semi-submersibles, jackup barges, barges, or platform rigs.
The first drillship was the Cuss 1
Project Mohole was an ambitious attempt to drill through the Earth's crust into the Mohorovičić discontinuity, and to provide an Earth science complement to the high profile Space Race. The project was initially led by the American Miscellaneous Society with funding from the National Science...
, and the fleet size has been growing ever since. By 2013 the worldwide fleet of drillships is expected to top 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 drilling. U.S. President Barack Obama
Barack Hussein Obama II is the 44th and current President of the United States. He is the first African American to hold the office. Obama previously served as a United States Senator from Illinois, from January 2005 until he resigned following his victory in the 2008 presidential election.Born in...
's decision in late March 2010 to expand U.S. domestic exploratory drilling seems likely to increase further developments of drillship technology.
Stena drillings 'DrillMAX ICE' being constructed by Samsung Heavy Industries
Samsung Heavy Industries
Samsung Heavy Industries or SHI is one of the largest shipbuilders in the world and one of the "Big Three" shipbuilders of South Korea...
in South Korea
The Republic of Korea , , is a sovereign state in East Asia, located on the southern portion of the Korean Peninsula. It is neighbored by the People's Republic of China to the west, Japan to the east, North Korea to the north, and the East China Sea and Republic of China to the south...
is to be the most expensive drillship built to date and is to complete exploration in Arctic regions when completed in 2012.