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 Petroleum, also known as crude oil or simply oil, is a naturally occurring, yellowish-black liquid chemical mixture found in geological formations, consisting mainly of hydrocarbons. The term ''petroleum'' refers both to naturally occurring un ...

that lies in rock formations beneath the seabed. Most commonly, the term is used to describe drilling activities on the

continental shelf A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an islan ...

, though the term can also be applied to drilling in lakes, inshore waters and inland seas. Offshore drilling presents all environmental challenges, both offshore and onshore from the produced

hydrocarbons In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic; their odor is usually faint, and may b ...

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 barges and swamp barges), combined drilling and production facilities either bottom founded or floating platforms, and deepwater mobile offshore drilling units (MODU) including

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 ...

s or

drillship 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 ...

s. These are capable of operating in water depths up to . In shallower waters the mobile units are anchored to the seabed; however, in water deeper than , the semi-submersibles and drillships are maintained at the required drilling location using dynamic positioning.

History

Around 1891, the first submerged oil wells were drilled from platforms built on piles in the fresh waters of the Grand Lake St. Marys in

Ohio Ohio ( ) is a U.S. state, state in the Midwestern United States, Midwestern region of the United States. It borders Lake Erie to the north, Pennsylvania to the east, West Virginia to the southeast, Kentucky to the southwest, Indiana to the ...

. 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 field extending under the Santa Barbara Channel in

California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

. 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 Erie Lake Erie ( ) is the fourth-largest lake by surface area of the five Great Lakes in North America and the eleventh-largest globally. It is the southernmost, shallowest, and smallest by volume of the Great Lakes and also has the shortest avera ...

in the 1900s and Caddo Lake in

Louisiana Louisiana ( ; ; ) is a state in the Deep South and South Central regions of the United States. It borders Texas to the west, Arkansas to the north, and Mississippi to the east. Of the 50 U.S. states, it ranks 31st in area and 25 ...

in the 1910s. Shortly thereafter wells were drilled in tidal zones along the

Texas Texas ( , ; or ) is the most populous U.S. state, state in the South Central United States, South Central region of the United States. It borders Louisiana to the east, Arkansas to the northeast, Oklahoma to the north, New Mexico to the we ...

and Louisiana gulf coast. The Goose Creek Oil Field near Baytown, Texas is one such example. In the 1920s drilling activities occurred from concrete platforms in

Venezuela Venezuela, officially the Bolivarian Republic of Venezuela, is a country on the northern coast of South America, consisting of a continental landmass and many Federal Dependencies of Venezuela, islands and islets in the Caribbean Sea. It com ...

's Lake Maracaibo. One of the oldest subsea wells is the Bibi Eibat well, which came on stream in 1923 in

Azerbaijan Azerbaijan, officially the Republic of Azerbaijan, is a Boundaries between the continents, transcontinental and landlocked country at the boundary of West Asia and Eastern Europe. It is a part of the South Caucasus region and is bounded by ...

. The well was located on an artificial island in a shallow portion of the

Caspian Sea The Caspian Sea is the world's largest inland body of water, described as the List of lakes by area, world's largest lake and usually referred to as a full-fledged sea. An endorheic basin, it lies between Europe and Asia: east of the Caucasus, ...

. In the early 1930s, the Texas Company developed the first mobile steel barges for drilling in the brackish coastal areas of the

Gulf of Mexico The Gulf of Mexico () is an oceanic basin and a marginal sea of the Atlantic Ocean, mostly surrounded by the North American continent. It is bounded on the northeast, north, and northwest by the Gulf Coast of the United States; on the southw ...

. In 1937, Pure Oil and its partner Superior Oil used a fixed platform to develop a field offshore of Calcasieu Parish, Louisiana in of water. In 1938,

Humble Oil Humble Oil and Refining Co. was an American oil company founded in 1911 in Humble, Texas. In 1919, a 50% interest in Humble was acquired by the Standard Oil of New Jersey which acquired the rest of the company in September 1959. The Humble bran ...

built a mile-long wooden trestle with railway tracks into the sea at McFadden Beach on the Gulf of Mexico, placing a derrick at its end – this was later destroyed by a hurricane. In 1945, concern for American control of its offshore oil reserves caused President

Harry Truman Harry S. Truman (May 8, 1884December 26, 1972) was the 33rd president of the United States, serving from 1945 to 1953. As the 34th vice president in 1945, he assumed the presidency upon the death of Franklin D. Roosevelt that year. Subsequen ...

to issue an Executive Order unilaterally extending American territory to the edge of its continental shelf, an act that effectively ended the 3-mile limit " freedom of the seas" regime. In 1946,

Magnolia ''Magnolia'' is a large genus of about 210 to 340The number of species in the genus ''Magnolia'' depends on the taxonomic view that one takes up. Recent molecular and morphological research shows that former genera ''Talauma'', ''Dugandiodendr ...

drilled at a site off the coast, erecting a platform in of water off St. Mary Parish, Louisiana. In early 1947, Superior Oil erected a drilling and production platform in of water some off Vermilion Parish, La. But it was Kerr-Magee, as operator for partners Phillips Petroleum and Stanolind Oil & Gas 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 , fixed platform rigs were built, until demands for drilling

equipment Equipment most commonly refers to a set of tool A tool is an Physical object, object that can extend an individual's ability to modify features of the surrounding environment or help them accomplish a particular task. Although many Tool use by ...

was needed in the to depth of the Gulf of Mexico, the first jack-up rigs began appearing from specialized offshore drilling contractors. The first

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 Company. 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 midway 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 1920s by Edward Robert Armstrong for the purpose of operating aircraft with an invention known as the 'seadrome'. The first purpose-built drilling

''Ocean Driller'' was launched in 1963 by ODECO.. Since then, many semi-submersibles have been purpose-designed for the drilling industry mobile offshore fleet. Deepwater drilling systems 2

The first offshore

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, etc.) available for service in the worldwide offshore rig fleet. One of the world's deepest hubs is currently the Perdido in the Gulf of Mexico, floating in of water. It is operated by

Royal Dutch Shell Shell plc is a British multinational oil and gas company, headquartered in London, England. Shell is a public limited company with a primary listing on the London Stock Exchange (LSE) and secondary listings on Euronext Amsterdam and the New ...

and was built at a cost of $3 billion. The deepest operational platform is the Petrobras America Cascade FPSO in the Walker Ridge 249 field in of water.

Drilling platforms

Types of offshore oil and gas structures

Offshore drilling is usually done from platforms generically known as mobile offshore drilling units (MODU), which can be of one of several formats, depending on the water depth: * Jackup rig * Submersible drilling rig *

Semi-submersible platform 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 dr ...

Drillship 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 ...

Main offshore fields

Notable offshore fields include: Northstar Offshore Island Beaufort Sea

* the

North Sea The North Sea lies between Great Britain, Denmark, Norway, Germany, the Netherlands, Belgium, and France. A sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and the Norwegian Se ...

* the

(offshore

Mississippi Mississippi ( ) is a U.S. state, state in the Southeastern United States, Southeastern and Deep South regions of the United States. It borders Tennessee to the north, Alabama to the east, the Gulf of Mexico to the south, Louisiana to the s ...

, and

Alabama Alabama ( ) is a U.S. state, state in the Southeastern United States, Southeastern and Deep South, Deep Southern regions of the United States. It borders Tennessee to the north, Georgia (U.S. state), Georgia to the east, Florida and the Gu ...

) *

(in the

Los Angeles Basin The Los Angeles Basin is a sedimentary Structural basin, basin located in Southern California, in a region known as the Peninsular Ranges. The basin is also connected to an wikt:anomalous, anomalous group of east–west trending chains of mountai ...

and Santa Barbara Channel, part of the Ventura Basin) * the Caspian Sea (notably some major fields offshore

) * the Campos and Santos Basins off the coasts of

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

Newfoundland Newfoundland and Labrador is the easternmost province of Canada, in the country's Atlantic region. The province comprises the island of Newfoundland and the continental region of Labrador, having a total size of . As of 2025 the population ...

and

Nova Scotia Nova Scotia is a Provinces and territories of Canada, province of Canada, located on its east coast. It is one of the three Maritime Canada, Maritime provinces and Population of Canada by province and territory, most populous province in Atlan ...

(

Atlantic Canada Atlantic Canada, also called the Atlantic provinces (), is the list of regions of Canada, region of Eastern Canada comprising four provinces: New Brunswick, Newfoundland and Labrador, Nova Scotia, and Prince Edward Island. As of 2021, the landma ...

) * several fields off

West Africa West Africa, also known as Western Africa, is the westernmost region of Africa. The United Nations geoscheme for Africa#Western Africa, United Nations defines Western Africa as the 16 countries of Benin, Burkina Faso, Cape Verde, The Gambia, Gha ...

most notably west of

Nigeria Nigeria, officially the Federal Republic of Nigeria, is a country in West Africa. It is situated between the Sahel to the north and the Gulf of Guinea in the Atlantic Ocean to the south. It covers an area of . With Demographics of Nigeria, ...

and

Angola Angola, officially the Republic of Angola, is a country on the west-Central Africa, central coast of Southern Africa. It is the second-largest Portuguese-speaking world, Portuguese-speaking (Lusophone) country in both total area and List of c ...

* offshore fields in

South East Asia Southeast Asia is the geographical United Nations geoscheme for Asia#South-eastern Asia, southeastern region of Asia, consisting of the regions that are situated south of China, east of the Indian subcontinent, and northwest of the Mainland Au ...

and Sakhalin, Russia * major offshore oil fields are located in the

Persian Gulf The Persian Gulf, sometimes called the Arabian Gulf, is a Mediterranean seas, mediterranean sea in West Asia. The body of water is an extension of the Arabian Sea and the larger Indian Ocean located between Iran and the Arabian Peninsula.Un ...

such as Safaniya, Manifa and Marjan which belong to Saudi Arabia and are developed by

Saudi Aramco Saudi Aramco ( ') or Aramco (formerly Arabian-American Oil Company), officially the Saudi Arabian Oil Company, is a majority state-owned petroleum and natural gas company that is the national oil company of Saudi Arabia. , it is the fourth- l ...

. * fields in

India India, officially the Republic of India, is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area; the List of countries by population (United Nations), most populous country since ...

(Mumbai High, K G Basin-East Coast Of India, Tapti Field,

Gujarat Gujarat () is a States of India, state along the Western India, western coast of India. Its coastline of about is the longest in the country, most of which lies on the Kathiawar peninsula. Gujarat is the List of states and union territories ...

, India) * the Taranaki Basin in

New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...

* the

Kara Sea The Kara Sea is a marginal sea, separated from the Barents Sea to the west by the Kara Strait and Novaya Zemlya, and from the Laptev Sea to the east by the Severnaya Zemlya archipelago. Ultimately the Kara, Barents and Laptev Seas are all ...

north of Siberia * the

Arctic Ocean The Arctic Ocean is the smallest and shallowest of the world's five oceanic divisions. It spans an area of approximately and is the coldest of the world's oceans. The International Hydrographic Organization (IHO) recognizes it as an ocean, ...

off the coasts of

Alaska Alaska ( ) is a non-contiguous U.S. state on the northwest extremity of North America. Part of the Western United States region, it is one of the two non-contiguous U.S. states, alongside Hawaii. Alaska is also considered to be the north ...

and Canada's

Northwest Territories The Northwest Territories is a federal Provinces and territories of Canada, territory of Canada. At a land area of approximately and a 2021 census population of 41,070, it is the second-largest and the most populous of Provinces and territorie ...

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 platform The Troll A platform is a Condeep gravity-based structure offshore natural gas platform in the Troll gas field off the west coast of Norway. Built from reinforced concrete, , it was the tallest structure that has ever been moved to another pos ...

standing on a depth of . 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 thousand 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 subsea, 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 had been inaccessible—and overcome challenges posed by sea ice such as in the

Barents Sea The Barents Sea ( , also ; , ; ) is a marginal sea of the Arctic Ocean, located off the northern coasts of Norway and Russia and divided between Norwegian and Russian territorial waters.World Wildlife Fund, 2008. It was known earlier among Russi ...

. One such challenge in shallower environments is seabed gouging by drifting ice features (means of protecting offshore installations against ice action includes burial in the seabed). 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 The petroleum industry, also known as the oil industry, includes the global processes of hydrocarbon exploration, exploration, extraction of petroleum, extraction, oil refinery, refining, Petroleum transport, transportation (often by oil tankers ...

, at least in the western world. These efforts among others are contained in the established term integrated operations. 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 spill An oil spill is the release of a liquid petroleum hydrocarbon into the environment, especially the marine ecosystem, due to human activity, and is a form of pollution. The term is usually given to marine oil spills, where oil is released into th ...

s from oil tankers or pipelines transporting oil from the platform to onshore facilities, and from leaks and accidents on the platform (e.g.

Deepwater Horizon oil spill The ''Deepwater Horizon'' oil spill was an environmental disaster off the coast of the United States in the Gulf of Mexico, on the BP-operated Macondo Prospect. It is considered the largest marine oil spill in the history of the petroleum in ...

and Ixtoc I oil spill). Produced water is also generated, which is water brought to the surface along with the oil and gas; it is usually highly saline and may include dissolved or unseparated hydrocarbons.

References

External links

Center for Biological Diversity v Dept of the Interior
17Apr2009 DC Appellate Decision stopping offshore Alaska Oil Leases.

* ttps://books.google.com/books?id=LQEAAAAAMBAJ&dq=popular+science+1930&pg=PA106 "New Oil from the Deep Ocean Floor."''Popular Science'', October 1975, pp. 106–108. {{DEFAULTSORT:Offshore Drilling Drilling technology Natural gas technology Petroleum production

History

Drilling platforms

Main offshore fields

Challenges

Effects on the environment

See also

References

External links