Prudhoe Bay Oil Field

Prudhoe Bay Oil Field is a large oil field on Alaska's North Slope. It is the largest oil field in North America, covering 213543 acre and originally contained approximately 25 Goilbbl of oil.[1] 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 and ConocoPhillips until August 2019; when BP sold all its Alaska assets to Hilcorp.[2]

Location

The field is located 400 mi north of Fairbanks and 650 mi north of Anchorage, 250 mi north of the Arctic Circle, and 358 mi south of the North Pole.[1]

Geology

The field is an anticline structure located on the Barrow Arch, with faulting on the north side of the arch and a Lower Cretaceous unconformity on the east.[39]

Claims on petroleum seeps 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, Eskimos, pointed out two large mounds fifty feet high and 200 feet in diameter.[40] Gold prospectors 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.[41] His report noted disputing claims by Standard Oil Company.[42] This led to the establishment of the Naval Petroleum Reserve No. 4 in 1923, after which the Navy engaged the United States Geological Survey to survey the area from 1923 until 1926, who concluded the best objectives were Cretaceous rocks.[43] 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.[44]

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.[45] 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".[46]

In 1968, Prudhoe Bay State No. 1 encountered the Permian-Triassic Sadlerochit formation at 8200 feet which flowed gas at 1.25 million cubic feet per day with 20–27 per cent porosity and "tens of millidarcies" permeability.[47] Oil, condensate and gas are produced from the Triassic, Ivishak sandstone. 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.[48] During the field's early life the oil-bearing sandstone in some locations was 600 ft thick. Today, the oil bearing zone's average thickness is about 60 ft and the initial estimate of Oil in place was 2.3 billion barrels.[49][50]

The original target of the Prudhoe Bay State No. 1 was the Mississippian Lisburne limestone, 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.[51] This initial oil was burned "because there wasn't ample storage", the flames of which were spotted by a passing airline.[52] The Department of Energy in 1991 estimated oil in place for this formation at 3.1 billion barrels.[53]

Statistics

Statistics for the Greater Prudhoe Bay Field:[1]

Discovery well: Prudhoe Bay State #1
Discovery date: December 26, 1967[54]
Step-out well March 1968 confirmed[54]
Production start: June 20, 1977
Total field area: 213543 acre
Oil production wells: 1114
Total capacity: 25 Goilbbl
Produced: 12 Goilbbl as of March 28, 2013
Total recoverable: 16 Goilbbl

August 2006 shutdown

The March 2006 oil spill led the United States Department of Transportation 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.[59] The damage required replacement of 16 of 22 mi 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.[60] 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.[60][61] 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 400000 oilbbl/d.

BP initially estimated up to 2 to 3 months before the pipelines would be fully operational.[60] This caused increases in world oil prices,[62] and BP revised the estimated operational date to January 2007.[63] London brent crude hit an intra-day high of $77.73/barrel, the all-time high, at that time, being $78.18/barrel. United States crude oil 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.[64]

No part of the Alaska Pipeline was affected, although Alyeska said that lower crude oil volumes could slow pumping during the BP shutdown.[65]

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.[66]

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.[67]

location map	Alaska
relief	yes
country	United States
region	Alaska North Slope
offonshore	onshore
coordinates	70.30667°N, -148.7325°W
operator	BP
partners	BP, ExxonMobil, ConocoPhillips
discovery	March 12, 1968 by ARCO and Exxon's Prudhoe Bay State #1 well
start production	June 20, 1977
peak year	1988
peakofproduction	1.5 Moilbbl/d
oil production bbl/d	319013
production year oil	2023
est oil bbl	25000
est gas bft	46500
formations	Sadlerochit Group

Prudhoe Bay Oil Field

Location

Leasing

History

Operations

Production

Associated oil fields

Geology

Statistics

March 2006 oil spill

August 2006 shutdown

See also

Further reading

External links

References