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Alaska Oil and Gas Conservation Commission

Alaska Department of Administration, Alaska Oil and Gas Conservation Commission
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AOGCC Pool Statistics
Prudhoe Bay Unit, Prudhoe Oil Pool
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Operator: BP Exploration (Alaska) Inc.
Index map
Discovery Well: Arco Alaska Inc.
  Prudhoe Bay State No. 1
  Permit No. 167-011
  API No. 50-029-20001-00-00
  Sec.10, T11N, R14E, UM

Depth: 12,005’ MD / 12,005' TVD

December 19, 1967

Status: Producing
Location: Central Arctic Slope Area Location Map Pool Location Map DNR Unit Map
Orders: List of Orders Summary - Annotated References  
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. As of February 2011, field production totaled nearly 11.3 billion barrels of oil. 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.

Regular oil production began in October 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 six months of 2010, the Prudhoe Oil Pool produced an average of 236,750 barrels of oil per day.

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. The Prudhoe Bay, Prudhoe Oil Pool encompasses, in ascending order, the Sadlerochit, Shublik and Sag River Formations.

The Sadlerochit Formation is Triassic-aged, and it consists of 300 to 600 feet of sandstone and conglomerate. The lower part of the Sadlerochit consists of a basal, prodelta 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 nonmarine alluvial environment. Most of the recoverable reserves of the Sadlerochit occur in these braided stream sediments, where porosity ranges from 20 to 24% and permeability ranges from 300 md to several darcys.

The Shublik Formation is also Triassic-aged, and it consists of organic- and phosphate-rich sandstone, muddy sandstone, mudstone, silty limestone, and limestone. These sediments were deposited in a low energy marine environment with high biologic productivity. 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’ in the south to about 70’ in the north, and reservoir conditions improve toward the northeast. Porosity and permeability average about 25% and 270 md, respectively. The overlying shale member consists of shale and mudstone. This member thins from about 70’ in the west to about 10’ in the main field area.

  Strat Column Type Log
Production: Prod Chart    

  Oil (bbls) NGL (bbls) Gas (mcf) Water (bbls)
Cumulative 11,363,635,703
578,1555,218 66,459,526,988 9,664,298,957
2005 Total
118,480,580 21,419,504 2,823,410,898 412,604,527
2006 Total
91,356,646 19,266,361 2,444,754,420 286,125,040
2007 Total
95,480,242 20,704,755 2,703,931,559 330,826,590
2008 Total
95,839,407 19,201,129 2,653,723,548 350,017,225
2009 Total
91,244,587 18,423,385 2,613,671,942 325,757,858
2010 Total
88,823,023 16,675,601 2,517,686,819 320,550,842
2011 Total
84,065,532 17,271,005 2,515,492,720 323,923,162
2007 Rate (b/d)
261,590 56,725 7,408,032 906,374
2008 Rate (b/d)
262,574 52,606 7,270,475 958,951
2009 Rate (b/d)
249,985 50,475 7,160,745 892,487
2010 Rate (b/d)
243,351 45,687 6,897,772 878,221
2011 Rate (b/d) 230,317 47,318 6,891,761 887,461
2008 Change (%)
0 -7 -2 6
2009 Change (%)
-5 -4 -2 -7
2010 Change (%)
-3 -9 -4 -2
2011 Change (%)
-5 4 0 1

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