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
hydrocarbonsPetroleum or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth's surface. Petroleum is recovered mostly through oil drilling...
which lie in rock formations beneath the seabed. Most commonly, the term is used to describe drilling activities on the
continental shelfThe continental shelf is the extended perimeter of each continent and associated coastal plain. Much of the shelf was exposed during glacial periods, but is now submerged under relatively shallow seas and gulfs, and was similarly submerged during other interglacial periods. The continental margin,...
, though the term can also be applied to drilling in lakes, inshore waters and inland seas.
Offshore drilling presents environmental challenges, both from the produced hydrocarbons and the materials used during the drilling operation. Controversies include the ongoing US offshore drilling debate.
There are many different types of facilities from which offshore drilling operations take place. These include bottom founded drilling rigs (
jackup bargesA jack-up rig is a type of mobile platform that is able to stand still on the sea floor, resting on a number of supporting legs. The most popular designs use 3 independent legs, although some jackups have 4 legs or more...
and swamp barges), combined drilling and production facilities either bottom founded or floating platforms and deepwater mobile offshore drilling units (MODU) including semi-submersibles and drillships. These are capable of operating in water depths up to 10,000 ft. In shallower waters the mobile units are anchored to the seabed, however in deeper water (>5,000 ft) the
semisubmersiblesA 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...
or
drillshipA drillship is a maritime vessel that has been fitted with drilling apparatus. It is most often used for exploratory offshore drilling of new oil or gas wells in deep water or for scientific drilling. The drillship can also be used as a platform to carry out well maintenance or completion work such...
s are maintained at the required drilling location using
dynamic positioningDynamic positioning is a computer controlled system to automatically maintain a vessel's position and heading by using its own propellers and thrusters...
.
History
Around 1891, the first submerged oil wells were drilled from platforms built on piles in the fresh waters of the
Grand Lake St. MarysGrand Lake Saint Marys State Park is an Ohio state park, west of St. Marys, and south-east of Celina, south-west of Lima in the north-western part of the U.S. state of Ohio.Grand Lake covers in Mercer and Auglaize counties...
(a.k.a. Mercer County Reservoir) in
OhioOhio is a Midwestern state in the United States. The 34th largest state by area in the U.S.,it is the 7th‑most populous with over 11.5 million residents, containing several major American cities and seven metropolitan areas with populations of 500,000 or more.The state's capital is Columbus...
. The wells were developed by small local companies such as Bryson, Riley Oil, German-American, and Banker's Oil.
Around 1896, the first submerged oil wells in salt water were drilled in the portion of the
Summerland fieldThe Summerland Oil Field is an inactive oil field in Santa Barbara County, California, about four miles east of the city of Santa Barbara, within and next to the unincorporated community of Summerland...
extending under the
Santa Barbara ChannelThe Santa Barbara Channel is a portion of the Pacific Ocean which separates the mainland of California from the northern Channel Islands. It is generally south of the city of Santa Barbara, and west of the city of Ventura....
in
CaliforniaCalifornia is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
. The wells were drilled from piers extending from land out into the channel.
Other notable early submerged drilling activities occurred on the Canadian side of
Lake ErieLake Erie is the fourth largest lake of the five Great Lakes in North America, and the tenth largest globally. It is the southernmost, shallowest, and smallest by volume of the Great Lakes and therefore also has the shortest average water residence time. It is bounded on the north by the...
in the 1900s and
Caddo LakeCaddo Lake is a lake and wetland located on the border between Texas and Louisiana, in northern Harrison County and southern Marion County in Texas and western Caddo Parish in Louisiana. The lake is named after the Southeastern culture of Native Americans called Caddoans or Caddo, who lived in...
in
LouisianaLouisiana is a state located in the southern region of the United States of America. Its capital is Baton Rouge and largest city is New Orleans. Louisiana is the only state in the U.S. with political subdivisions termed parishes, which are local governments equivalent to counties...
in the 1910s. Shortly thereafter wells were drilled in tidal zones along the
TexasTexas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...
and Louisiana
gulf coastThe Gulf Coast of the United States, sometimes referred to as the Gulf South, South Coast, or 3rd Coast, comprises the coasts of American states that are on the Gulf of Mexico, which includes Texas, Louisiana, Mississippi, Alabama, and Florida and are known as the Gulf States...
. The
Goose Creek Oil FieldThe Goose Creek Oil Field is a large oil field in Baytown, Texas, on Galveston Bay. Discovered in 1903, and reaching maximum production in 1918 after a series of spectacular gushers, it was one of the fields which contributed to the Texas Oil Boom of the early 20th century...
near
Baytown, TexasBaytown is a city within Harris County and partially in Chambers County in the Gulf Coast region of the U.S. state of Texas. Located within the Houston–Sugar Land–Baytown metropolitan area, it lies along both State Highway 146 and Interstate 10. As of 2010, Baytown had an population of 71,802...
is one such example. In the 1920s drilling activities occurred from concrete platforms in
VenezuelaVenezuela , officially called the Bolivarian Republic of Venezuela , is a tropical country on the northern coast of South America. It borders Colombia to the west, Guyana to the east, and Brazil to the south...
’s
Lake MaracaiboLake Maracaibo is a large brackish bay in Venezuela at . It is connected to the Gulf of Venezuela by Tablazo Strait at the northern end, and fed by numerous rivers, the largest being the Catatumbo. It is commonly considered a lake rather than a bay or lagoon, and at 13,210 km² it would be the...
.
One of the oldest subsea wells is the Bibi Eibat well, which came on stream in 1923 in
AzerbaijanAzerbaijan , officially the Republic of Azerbaijan is the largest country in the Caucasus region of Eurasia. Located at the crossroads of Western Asia and Eastern Europe, it is bounded by the Caspian Sea to the east, Russia to the north, Georgia to the northwest, Armenia to the west, and Iran to...
. The well was located on an artificial island in a shallow portion of the
Caspian SeaThe Caspian Sea is the largest enclosed body of water on Earth by area, variously classed as the world's largest lake or a full-fledged sea. The sea has a surface area of and a volume of...
. In the early 1930s, the Texas Co., later Texaco (now
ChevronChevron Corporation is an American multinational energy corporation headquartered in San Ramon, California, United States and active in more than 180 countries. It is engaged in every aspect of the oil, gas, and geothermal energy industries, including exploration and production; refining,...
) developed the first mobile steel barges for drilling in the brackish coastal areas of the Gulf of Mexico.
In 1937, Pure Oil (now
ChevronChevron Corporation is an American multinational energy corporation headquartered in San Ramon, California, United States and active in more than 180 countries. It is engaged in every aspect of the oil, gas, and geothermal energy industries, including exploration and production; refining,...
) and its partner Superior Oil (now
ExxonMobilExxon Mobil Corporation or ExxonMobil, is an American multinational oil and gas corporation. It is a direct descendant of John D. Rockefeller's Standard Oil company, and was formed on November 30, 1999, by the merger of Exxon and Mobil. Its headquarters are in Irving, Texas...
) used a fixed platform to develop a field 1 mile offshore of
Calcasieu Parish, LouisianaCalcasieu Parish[p] is a parish located in the U.S. state of Louisiana. The parish seat is Lake Charles. As of 2010, the parish population was 192,768...
in 14 feet of water.
In 1946, Magnolia Petroleum (now
ExxonMobilExxon Mobil Corporation or ExxonMobil, is an American multinational oil and gas corporation. It is a direct descendant of John D. Rockefeller's Standard Oil company, and was formed on November 30, 1999, by the merger of Exxon and Mobil. Its headquarters are in Irving, Texas...
) drilled at a site 18 miles off the coast, erecting a platform in 18 feet of water off
St. Mary Parish, LouisianaSt. Mary Parish is a parish located in the U.S. state of Louisiana. The parish seat is Franklin. As of 2000, the population was 53,500.The Morgan City Micropolitan Statistical Area includes all of St. Mary Parish.-Geography:...
.
In early 1947, Superior Oil erected a drilling and production platform in 20 feet of water some 18 miles off Vermilion Parish, La. But it was Kerr-McGee Oil Industries (now Anadarko Petroleum), as operator for partners Phillips Petroleum (
ConocoPhillipsConocoPhillips Company is an American multinational energy corporation with its headquarters located in the Energy Corridor district of Houston, Texas in the United States...
) and Stanolind Oil & Gas (
BPBP p.l.c. is a global oil and gas company headquartered in London, United Kingdom. It is the third-largest energy company and fourth-largest company in the world measured by revenues and one of the six oil and gas "supermajors"...
) that completed its historic Ship Shoal Block 32 well in October 1947, months before Superior actually drilled a discovery from their Vermilion platform farther offshore. In any case, that made Kerr-McGee’s well the first oil discovery drilled out of sight of land.
When offshore drilling moved into deeper waters of up to 100 feet, fixed platform rigs were built, until demands for drilling equipment was needed in the 100- to 400-foot depth of the Gulf of Mexico, the first
jack-up rigsA jack-up rig is a type of mobile platform that is able to stand still on the sea floor, resting on a number of supporting legs. The most popular designs use 3 independent legs, although some jackups have 4 legs or more...
began appearing from specialized offshore drilling contractors such as forerunners of ENSCO International.
The first
semi-submersibleA 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...
resulted from an unexpected observation in 1961. Blue Water Drilling Company owned and operated the four-column submersible Blue Water Rig No.1 in the Gulf of Mexico for
Shell Oil CompanyShell Oil Company is the United States-based subsidiary of Royal Dutch Shell, a multinational oil company of Anglo Dutch origins, which is amongst the largest oil companies in the world. Approximately 22,000 Shell employees are based in the U.S. The head office in the U.S. is in Houston, Texas...
. As the pontoons were not sufficiently buoyant to support the weight of the rig and its consumables, it was towed between locations at a draught mid-way between the top of the pontoons and the underside of the deck. It was noticed that the motions at this draught were very small, and Blue Water Drilling and Shell jointly decided to try operating the rig in the floating mode. The concept of an anchored, stable floating deep-sea platform had been designed and tested back in the 1920's by
Edward Robert ArmstrongEdward Robert Armstrong was a Canadian born engineer and inventor who in 1927 proposed a series of "seadrome" floating airport platforms for airplanes to land on and refuel for transatlantic flights...
for the purpose of operating aircraft with an invention known as the 'seadrome'. The first purpose-built drilling
semi-submersibleA 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...
Ocean Driller was launched in 1963. Since then, many semi-submersibles have been purpose-designed for the drilling industry mobile offshore fleet.
The first offshore
drillshipA drillship is a maritime vessel that has been fitted with drilling apparatus. It is most often used for exploratory offshore drilling of new oil or gas wells in deep water or for scientific drilling. The drillship can also be used as a platform to carry out well maintenance or completion work such...
was the
CUSS 1 developed for the Mohole project to drill into the Earth's crust.
As of June, 2010, there were over 620 mobile offshore drilling rigs (Jackups, semisubs, drillships, barges) available for service in the competitive rig fleet.
The world's deepest platform is currently the Perdido in the Gulf of Mexico, floating in 2,438 meters of water. It is operated by
Royal Dutch ShellRoyal Dutch Shell plc , commonly known as Shell, is a global oil and gas company headquartered in The Hague, Netherlands and with its registered office in London, United Kingdom. It is the fifth-largest company in the world according to a composite measure by Forbes magazine and one of the six...
and was built at a cost of $3 billion.
Main offshore fields
Notable offshore fields today are found in the
North SeaIn the southwest, beyond the Straits of Dover, the North Sea becomes the English Channel connecting to the Atlantic Ocean. In the east, it connects to the Baltic Sea via the Skagerrak and Kattegat, narrow straits that separate Denmark from Norway and Sweden respectively...
, the
Gulf of MexicoThe Gulf of Mexico is a partially landlocked ocean basin largely surrounded by the North American continent and the island of Cuba. It is bounded on the northeast, north and northwest by the Gulf Coast of the United States, on the southwest and south by Mexico, and on the southeast by Cuba. In...
, the
CamposCampos Basin is a petroleum rich area located offshore of Rio de Janeiro, Brazil. It has a total area of 100,000 square kilometres, with 40 fields discovered and operated by Petrobras....
and
Santos BasinThe Santos Basin is an offshore pre-salt basin. It is located in the south Atlantic Ocean, some south east of São Paulo, Brazil. One of the largest Brazilian sedimentary basins, it is the site of several recent significant oil fields, including Tupi and Jupiter....
s off the coasts of
BrazilBrazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
,
NewfoundlandNewfoundland and Labrador is the easternmost province of Canada. Situated in the country's Atlantic region, it incorporates the island of Newfoundland and mainland Labrador with a combined area of . As of April 2011, the province's estimated population is 508,400...
and
Nova ScotiaNova Scotia is one of Canada's three Maritime provinces and is the most populous province in Atlantic Canada. The name of the province is Latin for "New Scotland," but "Nova Scotia" is the recognized, English-language name of the province. The provincial capital is Halifax. Nova Scotia is the...
(
Atlantic CanadaAtlantic Canada is the region of Canada comprising the four provinces located on the Atlantic coast, excluding Quebec: the three Maritime provinces – New Brunswick, Prince Edward Island, and Nova Scotia – and Newfoundland and Labrador...
), several fields off
West AfricaWest Africa or Western Africa is the westernmost region of the African continent. Geopolitically, the UN definition of Western Africa includes the following 16 countries and an area of approximately 5 million square km:-Flags of West Africa:...
most notably west of
NigeriaNigeria , officially the Federal Republic of Nigeria, is a federal constitutional republic comprising 36 states and its Federal Capital Territory, Abuja. The country is located in West Africa and shares land borders with the Republic of Benin in the west, Chad and Cameroon in the east, and Niger in...
and
AngolaAngola, officially the Republic of Angola , is a country in south-central Africa bordered by Namibia on the south, the Democratic Republic of the Congo on the north, and Zambia on the east; its west coast is on the Atlantic Ocean with Luanda as its capital city...
, as well as offshore fields in South East Asia and
SakhalinSakhalin or Saghalien, is a large island in the North Pacific, lying between 45°50' and 54°24' N.It is part of Russia, and is Russia's largest island, and is administered as part of Sakhalin Oblast...
, Russia. Also major offshore oil fields are located in the
Persian GulfThe Persian Gulf, in Southwest Asia, is an extension of the Indian Ocean located between Iran and the Arabian Peninsula.The Persian Gulf was the focus of the 1980–1988 Iran-Iraq War, in which each side attacked the other's oil tankers...
such as Safaniya, Manifa, and Marjan which belong to Saudi Arabia and are developed by Saudi Aramco.
Challenges
Offshore oil and gas production is more challenging than land-based installations due to the remote and harsher environment. Much of the innovation in the offshore petroleum sector concerns overcoming these challenges, including the need to provide very large production facilities. Production and drilling facilities may be very large and a large investment, such as the
Troll A platformThe Troll A platform is a condeep offshore natural gas platform in the Troll gas field off the west coast of Norway. It is the tallest construction that has ever been moved to another position, relative to the surface of the Earth, and is among the largest and most complex engineering projects in...
standing on a depth of 300 meters.
Another type of offshore platform may float with a mooring system to maintain it on location. While a floating system may be lower cost in deeper waters than a fixed platform, the dynamic nature of the platforms introduces many challenges for the drilling and production facilities.
The ocean can add several hundred meters or more to the fluid column. The addition increases the equivalent circulating density and downhole pressures in drilling wells, as well as the energy needed to lift produced fluids for separation on the platform.
The trend today is to conduct more of the production operations
subseaSubsea is a general term frequently used to refer to equipment, technology, and methods employed in marine biology, undersea geology, offshore oil and gas developments, underwater mining, and offshore wind power industries.- Oil and gas :...
, by separating water from oil and re-injecting it rather than pumping it up to a platform, or by flowing to onshore, with no installations visible above the sea. Subsea installations help to exploit resources at progressively deeper waters, locations which have been inaccessible, and overcome challenges posed by sea ice, such as in the
Barents SeaThe Barents Sea is a marginal sea of the Arctic Ocean, located north of Norway and Russia. Known in the Middle Ages as the Murman Sea, the sea takes its current name from the Dutch navigator Willem Barents...
.
Offshore manned facilities also present logistics and human resources challenges. An offshore oil platform is a small community in itself with cafeteria, sleeping quarters, management, and other support functions. In the North Sea, staff members are transported by helicopter for a two-week shift. They usually receive higher salary than onshore workers do. Supplies and waste are transported by ship, and the supply deliveries need to be carefully planned because storage space on the platform is limited. Today, much effort goes into relocating as many of the personnel as possible onshore, where management and technical experts are in touch with the platform by video conferencing. An onshore job is also more attractive for the aging workforce in the petroleum industry, at least in the western world. These efforts among others are contained in the established term
integrated operationsIn the Petroleum industry, Integrated operations refers to new work processes and ways of doing oil and gas exploration and production, which has been facilitated by new information and communication technology. Multi-discipline collaboration in plant operation is one example...
. The increased use of subsea facilities helps achieve the objective of keeping more workers onshore. Subsea facilities are also easier to expand, with new separators or different modules for different oil types, and are not limited by the fixed floor space of an above-water installation.
Effects on the environment
Offshore oil production involves environmental risks, most notably
oil spillAn oil spill is the release of a liquid petroleum hydrocarbon into the environment, especially marine areas, due to human activity, and is a form of pollution. The term is mostly used to describe marine oil spills, where oil is released into the ocean or coastal waters...
s from oil tankers or pipelines transporting oil from the platform to onshore facilities, and from leaks and accidents on the platform.
Produced waterProduced water is a term used in the oil industry to describe water that is produced along with the oil and gas. Oil and gas reservoirs have a natural water layer that lies under the hydrocarbons. Oil reservoirs frequently contain large volumes of water, while gas reservoirs tend to have smaller...
is also generated, which is excess water from oil or gas production and includes varying amounts of oil, or other chemicals used in, or resulting from, oil production. According to the organization Culture Change, a
Gulf of MexicoThe Gulf of Mexico is a partially landlocked ocean basin largely surrounded by the North American continent and the island of Cuba. It is bounded on the northeast, north and northwest by the Gulf Coast of the United States, on the southwest and south by Mexico, and on the southeast by Cuba. In...
rig dumps about 90,000 tons of
drilling fluidIn geotechnical engineering, drilling fluid is a fluid used to aid the drilling of boreholes into the earth. Often used while drilling oil and natural gas wells and on exploration drilling rigs, drilling fluids are also used for much simpler boreholes, such as water wells. Liquid drilling fluid...
and cuttings over its lifetime, with its wells also contributing with heavy metals. See ecological effects of oil platforms.
See also
- Deep sea mining
- Jackup barge
- Offshore oil and gas in the United States
Offshore oil and gas in the United States provides a large portion of the nation’s oil and gas supply. Large oil and gas reservoirs are found in the sea nearby Louisiana, Texas, California, and Alaska...
- Oil drilling
- Oil platform
An oil platform, also referred to as an offshore platform or, somewhat incorrectly, oil rig, is a lаrge structure with facilities to drill wells, to extract and process oil and natural gas, and to temporarily store product until it can be brought to shore for refining and marketing...
- Drillship
A drillship is a maritime vessel that has been fitted with drilling apparatus. It is most often used for exploratory offshore drilling of new oil or gas wells in deep water or for scientific drilling. The drillship can also be used as a platform to carry out well maintenance or completion work such...
- 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...
- Shallow water drilling
Shallow water drilling is the process of oil and gas exploration and production in less than 500 feet of water.Shallow water drilling differs from deepwater drilling in several key aspects...
- Subsea
Subsea is a general term frequently used to refer to equipment, technology, and methods employed in marine biology, undersea geology, offshore oil and gas developments, underwater mining, and offshore wind power industries.- Oil and gas :...
External links