Alaska Department of Administration

Alaska Oil and Gas Conservation Commission

AOGCC Pool Statistics

Prudhoe Bay, Prudhoe Oil Pool


Operator
BP EXPLORATION (ALASKA) INC.
Discovery Well
ARCO ALASKA INC
PRUDHOE BAY ST 1
Permit No.167-011
API No. 50-029-20001-00-00
Sec. 10, T11, R14E, UM
Depth: 12005' MD / 12005' TVD
June 24, 1968
Map of Prudhoe Bay, Prudhoe Oil Pool

Summary

Prudhoe Bay is the largest oil field in North America, and it ranks among the 20 largest fields in the world. The operator, BP, estimates the original oil in place to be about 25 billion barrels, and gas in place is estimated to be 46 trillion cubic feet.1 Through December 2015, cumulative production from the Prudhoe Bay Field totaled nearly 12.6 billion barrels of oil, and the Prudhoe Oil Pool contributed nearly 11.7 billion barrels to this total.2 Associated produced water and most of the associated produced gas are currently re-injected to maintain reservoir pressure.

The Prudhoe Bay State No. 1 exploratory well discovered this pool in 1968. In that well, DST No. 12 (a 48-1/2 hour production test that began June 1, 1968) produced oil at a maximum rate of 2,415 barrels per day, with an average estimated rate of about 2,025 barrels per day.3

Regular oil production began in April 1969, exceeded an average rate of 1,000,000 barrels per day in March of 1978, and then peaked in January 1987 at 1,627,036 barrels per day. In March 1994, oil production from the pool dropped below 1,000,000 barrels per day. For the last three months of 2010, the Prudhoe Oil Pool produced an average of 257,150 barrels of oil per day. Between 2009 and 2013, Prudhoe Bay dropped from first place to third place amongst all U.S. oil fields, falling behind two Texas oil fields, the Eagle Ford Shale Play and the Sprayberry Trend.4 For the last three months of 2015, the Prudhoe Oil Pool averaged 218,100 barrels of oil per day.5

In October 2015, the AOGCC approved Conservation Order No. 341F, which increased the allowable annual average gas offtake rate from the Prudhoe Oil Pool from 2.7 to 3.6 billion standard cubic feet of gas per day to adequate capacity to meet the anticipated gas sales requirements for the proposed Alaska LNG project. That same order determined the carbon dioxide within the Alaska LNG gas treatment plant effluent stream would prove to be a very valuable resource for enhanced recover projects on the North Slope of Alaska.6 At that same time, the AOGCC also approved Area Injection Order Nos. 3B and 4G, which authorized injection of carbon dioxide and other gas treatment plant effluent gasses from sources within or outside of the Prudhoe Bay Unit to be injected into the Prudhoe Oil Pool for purposes of pressure maintenance and enhanced oil recovery.7,8

Production

Geology

The Prudhoe Oil Pool is defined as the accumulations of oil that are common to and which correlate with the accumulations found in the Atlantic Richfield - Humble Prudhoe Bay State No. 1 well between the depths of 8,110 and 8,680 feet.9 The Prudhoe Bay, Prudhoe Oil Pool encompasses, in ascending order, the Sag River, Shublik and Ivishak Formations.

The Sag River Formation consists of a lower sandstone member and an upper shale member. The sandstone member consists of uniform, well-sorted, fine-grained sandstone and siltstone that were deposited within a barrier beach complex. The Sag River Formation forms a relatively continuous reservoir over a large part of the Prudhoe Bay Field. The sandstone member thickens from 20 feet in the south to about 70 feet in the north, and reservoir conditions improve toward the northeast.10 Porosity and permeability average about 25% and 270 md, respectively.11 The overlying shale member consists of shale and mudstone. This member thins from about 70’ in the west to about 10 feet in the main field area.

The Shublik Formation is also Triassic-aged, and it consists of organic- and phosphate-rich sandstone, muddy sandstone, mudstone, silty limestone, and limestone.12 These sediments were deposited in a low energy marine environment that had a high level of biologic productivity.13,14

The Ivishak Formation is Triassic-aged, and it consists of 300 to 600 feet of sandstone and conglomerate.15 The lower part of the Ivishak consists of a basal, pro-delta marine unit that grades upward into a marginal marine coastal sequence consisting of interbedded sandstone and shale. The upper part was deposited by rivers and braided streams in a non-marine alluvial environment. Most of the recoverable reserves of the Ivishak occur in these braided stream sediments, where porosity ranges from 20 to 24% and permeability ranges from 300 millidarcies to several darcies.16


Last Revised
9 Feb 2016 SFD

1BP, 2003, North Slope Oil Fields, published as alaska_north_slope_oilfields[1].pdf
2Alaska Oil and Gas Conservation Commission, 2011, Production Database
3Alaska Oil and Gas Conservation Commission, 2005, Well File No. 1670110, Prudhoe Bay State No. 1
4Rosen, Y., 2015, Prudhoe Bay Loses Top Spot Among U.S. Oil Fields; Anchorage Daily News, http://www.adn.com/article/20150407/prudhoe-bay-loses-top-spot-among-us-oil-fields, accessed February 9, 2016
5Alaska Oil and Gas Conservation Commission, 2015, Production Database
6Alaska Oil and Gas Conservation Committee, 1977, Conservation Order No. 145, Prudhoe Bay Field, Prudhoe Bay Oil Pool
7Alaska Oil and Gas Conservation Commission, 2015, Area Injection Order No. 3B, Prudhoe Bay Field, Prudhoe Bay Oil Pool
8Alaska Oil and Gas Conservation Commission, 2015, Area Injection Order No. 4G, Prudhoe Bay Field, Prudhoe Bay Oil Pool
9Alaska Oil and Gas Conservation Committee, 1977, Conservation Order No. 145, Prudhoe Bay Field, Prudhoe Bay Oil Pool
10Jones, H.P. and Speers, R.B., 1976, Permo-Triassic Reservoirs of the Prudhoe Bay Field, North Slope, Alaska; in Braunstein, J., editor, North American Oil and Gas Fields; American Association Petroleum Geologists Memoir 24, p. 23 - 50
11Jamison, H.C., Brockett, L.D. and McIntosh, R. A., 1980, Prudhoe Bay - a Ten-Year Perspective; American Association of Petroleum Geologists, Memoir No. 30, p. 289 - 314
12Parrish, J.T., Whalen, M.T., and Hulm, E.J, 2001, Shublik Formation Lithofacies, Environments, and Sequence Stratigraphy, Arctic Alaska, U.S.A., in Houseknecht, D.W., NPRA Core Workshop, SEPM Core Workshop No. 21
13Jones, H.P. and Speers, R.B., 1976, Permo-Triassic Reservoirs of the Prudhoe Bay Field, North Slope, Alaska; in Braunstein, J., editor, North American Oil and Gas Fields; American Association Petroleum Geologists Memoir 24, p. 23 - 50
14Parrish, J.T., Whalen, M.T., and Hulm, E.J, 2001, Shublik Formation Lithofacies, Environments, and Sequence Stratigraphy, Arctic Alaska, U.S.A., in Houseknecht, D.W., NPRA Core Workshop, SEPM Core Workshop No. 21
15Van Poollen and Associates, Inc. and State of Alaska Division of Oil and Gas, 1974, In Place Volumetric Determination of Reservoir Fluids, Sadlerochit Formation, Prudhoe Bay Field
16Morgridge, D.L. and Smith, W.B., Jr., 1972, Geology and Discovery of Prudhoe Bay Field, Eastern Arctic Slope, Alaska, in King, R.E., editor, Stratigraphic Oil and Gas Fields; American Association of Petroleum Geologists Memoir No. 16, p. 489 - 501