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Prudhoe Bay Oil Field is a large
oil field A petroleum reservoir or oil and gas reservoir is a subsurface accumulation of hydrocarbons contained in porous or fractured rock formations. Such reservoirs form when kerogen (ancient plant matter) is created in surrounding rock by the prese ...
on
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 ...
's North Slope. It is the largest oil field in North America, covering and originally contained approximately of oil.Prudhoe Bay Fact Sheet
. BP. August 2006. (Adobe Acrobat *.PDF document)
The amount of recoverable oil in the field is more than double that of the next largest field in the United States by acreage (the East Texas Oil Field), while the largest by reserves is the Permian Basin (North America). The field was operated by BP; partners were
ExxonMobil Exxon Mobil Corporation ( ) is an American multinational List of oil exploration and production companies, oil and gas corporation headquartered in Spring, Texas, a suburb of Houston. Founded as the Successors of Standard Oil, largest direct s ...
and
ConocoPhillips ConocoPhillips Company is an American multinational corporation engaged in hydrocarbon exploration and production. It is based in the Energy Corridor district of Houston, Texas. The company has operations in 15 countries and has production in t ...
until August 2019; when BP sold all its Alaska assets to Hilcorp.


Location

The field is located north of Fairbanks and north of
Anchorage Anchorage, officially the Municipality of Anchorage, is the most populous city in the U.S. state of Alaska. With a population of 291,247 at the 2020 census, it contains nearly 40 percent of the state's population. The Anchorage metropolita ...
, north of the
Arctic Circle The Arctic Circle is one of the two polar circles, and the northernmost of the five major circle of latitude, circles of latitude as shown on maps of Earth at about 66° 34' N. Its southern counterpart is the Antarctic Circle. The Arctic Circl ...
, and south of the
North Pole The North Pole, also known as the Geographic North Pole or Terrestrial North Pole, is the point in the Northern Hemisphere where the Earth's rotation, Earth's axis of rotation meets its surface. It is called the True North Pole to distingu ...
. It is on the North Slope and lies between the National Petroleum Reserve–Alaska to the west and the
Arctic National Wildlife Refuge The Arctic National Wildlife Refuge (ANWR, pronounced as “''ANN-warr''”) or Arctic Refuge is a national wildlife refuge in northeastern Alaska, United States, on traditional Inupiaq, Iñupiaq and Gwichʼin, Gwich'in lands. The refuge is of ...
to the east. It is accessible by road from Fairbanks, Alaska via the
Elliott Highway The Elliott Highway is a highway in the U.S. state of Alaska that extends 152 miles (245 km) from Fox, about 10 miles (16 km) north of Fairbanks, to Manley Hot Springs. It was completed in 1959 and is part of Alaska Route 2. Rou ...
and
Dalton Highway The James W. Dalton Highway, usually referred to as the Dalton Highway (and signed as Alaska Route 11), is a road in Alaska. It begins at the Elliott Highway, north of Fairbanks, and ends at Deadhorse (an unincorporated community within t ...
.


Leasing

The State of Alaska owns the land and leases the area as the Prudhoe Bay Unit.Staff, Alaska Oil and Gas Conservation Commission.
Oil and Gas Pools – Statistics Pages
Accessed April 14, 2013
In the terminology that the State of Alaska uses in its leasing program, the "Prudhoe Bay Oil Field" is called the Prudhoe Bay Oil Pool. Oil pools within the Prudhoe Bay Unit include the following – maps showing the location of each pool are in the associated reference.


History

The area was originally identified as a potential oil field and selected in the early 1960s as part of the 100 million acres the federal government allotted to the new state of Alaska under the Alaska Statehood Act as a form of economic support. Tom Marshall, a key state employee tasked with selecting the 100 million acres, said the geology reminded him of big oil basins he'd seen in Wyoming. Commercial oil exploration started in Prudhoe Bay area in the 1960s and, after a number of fruitless years, a rig produced a natural gas flare in December 1967. The oil field was confirmed on March 12, 1968, by
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 ...
(which later became part of
Exxon Exxon Mobil Corporation ( ) is an American multinational oil and gas corporation headquartered in Spring, Texas, a suburb of Houston. Founded as the largest direct successor of John D. Rockefeller's Standard Oil, the modern company was form ...
) and Atlantic Richfield Company (ARCO), with the well Prudhoe Bay State #1. ARCO was the operating partner. Drilling sites for the discovery and confirmation wells were staked by geologist Marvin Mangus. BP was among the companies that had been active in the region, and BP was able to establish itself as a major player in the western part of the Prudhoe field. The field was initially operated as two separate developments, the BP Western Operating Area and the ARCO Eastern Operating Area. Upon acquisition of ARCO by BP and sale of ARCO Alaska assets to Phillips Petroleum in 2000, the two operating areas were consolidated and BP became the sole operator of the field.International Mapping on behalf of BP
BP in Alaska, animated map
In 1974 the State of Alaska's Division of Geological & Geophysical Surveys estimated that the field held of oil and of natural gas. Production did not begin until June 20, 1977 when the Alaska Pipeline was completed. The site of the field's discovery was listed on the
National Register of Historic Places The National Register of Historic Places (NRHP) is the Federal government of the United States, United States federal government's official United States National Register of Historic Places listings, list of sites, buildings, structures, Hist ...
in 2000, and has a commemorative marker. A well was operated at that site until 1985.


Operations

The field was initially operated as two separate developments, the BP Western Operating Area (WOA: Oil Rim) and the ARCO Eastern Operating Area (EOA: Gas Cap). Upon the acquisition of ARCO by BP and the sale of ARCO Alaska assets to Phillips Petroleum in 2000, the two operating areas were consolidated and BP became the sole operator of the field. In the field, oil is moved through pipelines from about 1000 wells to a pumping station at the head of the Trans-Alaska Pipeline; "flow lines" carry oil from the wells to local processing centers, then through "transit lines" to the pumping station. According to a 2007 recording of a BP representative, to replace the "huge volume of material" BP removes from beneath the ground, seawater is injected that is collected from Prudhoe Bay.


Production

North Slope oil production peaked in 1989 at (Greater Prudhoe Bay: , but had fallen to in 2005, while Greater Prudhoe averaged in December 2006 and Prudhoe itself averaged . Total production from 1977 through 2005 was . As of August 2006, BP estimated that of recoverable oil remain and can be recovered with current technology. Hilcorp energy is the field operator at Prudhoe Bay and has engaged in an aggressive redevelopment of the aging field since taking over as operator in mid-2019 from BP. Prudhoe Bay production was in February compared with barrels per day in January and barrels per day year-over-year in February, 2021.


Associated oil fields

The Milne Point oil field is west of Prudhoe Bay and the leased area, called the Milne Point Unit by the State of Alaska, includes the Kuparuk River Oil Pool,Staff, Alaska Oil and Gas Conservation Commission.
AOGCC Pool Statistics, Milne Point Unit, Kuparuk River Oil Pool
Sag River Oil Pool,Staff, Alaska Oil and Gas Conservation Commission.

and the Schrader Bluff Oil Pool.Staff, Alaska Oil and Gas Conservation Commission.

The
source rock In petroleum geology, source rock is a sedimentary rock which has generated hydrocarbons or which has the potential to generate hydrocarbons. Source rocks are one of the necessary elements of a working petroleum system. They are organic-rich sedim ...
for the Prudhoe Bay Oil Field and neighboring reserves is a potential source for
tight oil Tight oil (also known as shale oil, shale-hosted oil or light tight oil, abbreviated LTO) is light crude oil contained in Unconventional (oil & gas) reservoir, unconventional petroleum-bearing formations of low Permeability (earth sciences), perme ...
and
shale gas Shale gas is an unconventional natural gas that is found trapped within shale formations. Since the 1990s, a combination of horizontal drilling and hydraulic fracturing has made large volumes of shale gas more economical to produce, and ...
. As of 2013 mineral rights to 500,000 acres overlying the North Slope oil shale had been leased by Great Bear Petroleum whose principal is the petroleum geologist Ed Duncan. Paul Basinski, who has been called "one of the fathers of fracking", drove the exploration of fracking of the highly radioactive zone shale (HRZ shale) at Prudhoe Bay Oil Field; he died in 2018 of complications following a heart transplant.


Geology

The field is an
anticline In structural geology, an anticline is a type of Fold (geology), fold that is an arch-like shape and has its oldest Bed (geology), beds at its core, whereas a syncline is the inverse of an anticline. A typical anticline is convex curve, c ...
structure located on the Barrow Arch, with
faulting In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic ...
on the north side of the arch and a
Lower Cretaceous Lower may refer to: * ''Lower'' (album), 2025 album by Benjamin Booker * Lower (surname) * Lower Township, New Jersey *Lower Receiver (firearms) * Lower Wick Gloucestershire, England See also * Nizhny {{Disambiguation ...
unconformity An unconformity is a buried erosional or non-depositional surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval ...
on the east. Claims on
petroleum seep A petroleum seep is a place where natural liquid or gaseous hydrocarbons escape to the Earth's atmosphere and surface, normally under low pressure or flow. Seeps generally occur above either natural terrestrial or underwater petroleum accumu ...
s in the Cape Simpson area were first made in 1915 by a group consisting of T.L. Richardson, W.B. Van Valen, O. Hansen, B. Panigeo and Egowa after these last two,
Eskimo ''Eskimo'' () is a controversial Endonym and exonym, exonym that refers to two closely related Indigenous peoples: Inuit (including the Alaska Native Iñupiat, the Canadian Inuit, and the Greenlandic Inuit) and the Yupik peoples, Yupik (or Sibe ...
s, pointed out two large mounds fifty feet high and 200 feet in diameter.
Gold Gold is a chemical element; it has chemical symbol Au (from Latin ) and atomic number 79. In its pure form, it is a brightness, bright, slightly orange-yellow, dense, soft, malleable, and ductile metal. Chemically, gold is a transition metal ...
prospectors Prospecting is the first stage of the geological analysis (followed by exploration) of a territory. It is the search for minerals, fossils, precious metals, or mineral specimens. It is also known as fossicking. Traditionally prospecting rel ...
Smith and Berry also discovered these seeps and formed an investment group in San Francisco led by R.D. Adams, who funded an investigation led by the geologist H.A. Campbell. His report noted disputing claims by
Standard Oil Company Standard Oil Company was a corporate trust in the petroleum industry that existed from 1882 to 1911. The origins of the trust lay in the operations of the Standard Oil Company (Ohio), which had been founded in 1870 by John D. Rockefeller. The ...
. This led to the establishment of the Naval Petroleum Reserve No. 4 in 1923, after which the Navy engaged the
United States Geological Survey The United States Geological Survey (USGS), founded as the Geological Survey, is an agency of the U.S. Department of the Interior whose work spans the disciplines of biology, geography, geology, and hydrology. The agency was founded on Mar ...
to survey the area from 1923 until 1926, who concluded the best objectives were
Cretaceous The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...
rocks. From 1943 until 1953, the Navy drilled eighty wells, including the area at Cape Simpson and Umiat but none flowed more than 250 barrels per day. The discovery of the Swanson River Oil Field on the Kenai Peninsula in 1957 by the Richfield Oil Corporation prompted the company to send geologists to the Arctic starting in 1959 and seismic survey crews in 1963, which recorded a reconnaissance line across what was identified as the Prudhoe structure in 1964. In 1965, during the state lease sale, Richfield partnered with Humble Oil and acquired leases over what was later identified as the gas cap while BP was awarded leases over the "oil ring". In 1968, Prudhoe Bay State No. 1 encountered the
Permian The Permian ( ) is a geologic period and System (stratigraphy), stratigraphic system which spans 47 million years, from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.902 Mya. It is the s ...
-
Triassic The Triassic ( ; sometimes symbolized 🝈) is a geologic period and system which spans 50.5 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.4 Mya. The Triassic is t ...
Sadlerochit formation at 8200 feet which flowed gas at 1.25 million cubic feet per day with 20–27 per cent
porosity Porosity or void fraction is a measure of the void (i.e. "empty") spaces in a material, and is a fraction of the volume of voids over the total volume, between 0 and 1, or as a percentage between 0% and 100%. Strictly speaking, some tests measure ...
and "tens of millidarcies" permeability. Oil, condensate and gas are produced from the Triassic, Ivishak
sandstone Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...
. This reservoir was deposited as a complex amalgamation of fan deltas and alluvial fans. The continuity of this fan delta was shown to extend seven miles away when the ARCO-Humble Sag River State No. 1 well was drilled. During the field's early life the oil-bearing sandstone in some locations was thick. Today, the oil bearing zone's average thickness is about and the initial estimate of
Oil in place Oil in place (OIP) (not to be confused with original oil-in-place (OOIP)) is a specialist term in petroleum geology that refers to the total oil content of an oil reservoir. As this quantity cannot be measured directly, it has to be estimated from ...
was 2.3 billion barrels. The original target of the Prudhoe Bay State No. 1 was the Mississippian Lisburne
limestone Limestone is a type of carbonate rock, carbonate sedimentary rock which is the main source of the material Lime (material), lime. It is composed mostly of the minerals calcite and aragonite, which are different Polymorphism (materials science) ...
, encountered at 8,800 feet and flowed 1,152 barrels of oil per day in the 9,505 to 9,825 foot interval along with 1.3 million cubic feet of gas. This initial oil was burned "because there wasn't ample storage", the flames of which were spotted by a passing airline. The Department of Energy in 1991 estimated oil in place for this formation at 3.1 billion barrels.


Statistics

Statistics for the Greater Prudhoe Bay Field: * Discovery well: Prudhoe Bay State #1 * Discovery date: December 26, 1967"The Prize" Daniel Yergin * Step-out well March 1968 confirmed * Production start: June 20, 1977 * Total field area: * Oil production wells: 1114 * Total capacity: ** Produced: as of March 28, 2013 ** Total recoverable: ** Remaining recoverable: * Peak production: 1.97 million barrels per day (1988) * Natural gas: ** Total: (estimated) ** Recoverable: * Greater Prudhoe Bay satellite fields: ** East Operating Area (formerly ARCO)(production start date: 1977) ** West Operating Area (BP Exploration)(production start date: 1977) ** Midnight Sun (production start date: 1998) ** Aurora (production start date: 2000) ** Orion (production start date: 2002) ** Polaris (production start date: 1999) ** Borealis (production start date: 2001) * Ownership: ** BP Exploration (Operator): 26% ** ConocoPhillips.: 36% ** ExxonMobil: 36% ** Others: 2% *On 27 August 2019 BP announces the agreement to sell all its Alaska operations and interests to Hilcorp for $5.6 billion. The transaction includes interests in giant Prudhoe Bay field and Trans Alaska Pipeline.


March 2006 oil spill

On March 2, 2006, a worker for BP Exploration (Alaska) discovered an oil spill in western Prudhoe Bay. Up to were spilled, making it the largest oil spill on Alaska's north slope to date. The spill was attributed to a pipeline rupture. In October 2007, BP was found guilty of a misdemeanor violation of the Clean Water Act to resolve criminal liability relating to pipeline leaks of crude oil. As a result of the guilty plea, BP Alaska agreed to pay $20 million which included the criminal fine, community service payments and criminal restitution.


August 2006 shutdown

The March 2006 oil spill led the
United States Department of Transportation The United States Department of Transportation (USDOT or DOT) is one of the executive departments of the U.S. federal government. It is headed by the secretary of transportation, who reports directly to the president of the United States a ...
to mandate that the transit lines be inspected for corrosion. As a result, BP announced on 6 August 2006 they had discovered severe corrosion, with losses of 70 to 81 percent in the 3/8-inch thickness of the pipe walls. Oil leaking was reported in one area, with the equivalent of four to five barrels of oil spilled. The damage required replacement of 16 of of pipeline at the Prudhoe Bay. BP said it was surprised to find such severe corrosion and that it had been 14 years since they had used a pipeline inspection gauge ("pig") to clean out its lines because the company believed the use of the pigging equipment might damage pipe integrity. BP Exploration announced that they were shutting down the oil field indefinitely, due to the severe corrosion and a minor leak in the oil transit lines. This led to an 8% reduction in the amount of oil produced by the United States, as Prudhoe Bay was the country's largest oil producer, producing over . BP initially estimated up to 2 to 3 months before the pipelines would be fully operational. This caused increases in world oil prices, and BP revised the estimated operational date to January 2007. London
brent crude Brent Crude may refer to any or all of the components of the Brent Complex, a physically and financially traded oil market based around the North Sea of Northwest Europe; colloquially, Brent Crude usually refers to the price of the ICE (Intercon ...
hit an intra-day high of $77.73/barrel, the all-time high, at that time, being $78.18/barrel. United States
crude oil 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 u ...
peaked at $76.67/barrel. The state of Alaska, which gets most of its revenue from taxing the oil industry, lost as much as $6.4 million each day until production restarted. No part of the Alaska Pipeline was affected, although Alyeska said that lower crude oil volumes could slow pumping during the BP shutdown. The field has since reopened. In mid-June 2007, however, a small leak occurred in one of the pipelines that connect the field to the Trans-Alaska Pipeline, shutting down the field for a week. In March 2009 the State of Alaska sued BP in matter number 3AN-09-06181-CI alleging that BP was negligent in its management of rigging operations and corrosion control in the transit lines leading from the field into pumping station one of the Trans Alaska Pipeline. The state is seeking damages for lost royalty and tax revenues. The case seems to have been dismissed in 2010.


See also

* Mount Elbert Gas Hydrate Site


References


Further reading

* Jamison, H.C., Brockett, L.D., and McIntosh, R.A., 1980, Prudhoe Bay – A 10-Year Perspective, in Giant Oil and Gas Fields of the Decade: 1968–1978, AAPG Memoir 30, Tulsa: American Association of Petroleum Geologists, . *


External links


Oil and Gas Resources of the Arctic Alaska Petroleum Province

NPRA

Milne Point goes mainstream. Inc. oilfield
('' Alaska Business Monthly'', April 1995.)
Prudhoe Bay, Alaska
Aerial photos from the Prudhoe Bay area, July 2010 {{Petroleum industry 1968 establishments in Alaska ARCO BP oil and gas fields ConocoPhillips oil and gas fields ExxonMobil oil and gas fields Geography of North Slope Borough, Alaska Industry in the Arctic Oil fields in Alaska