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Alaska Oil and Gas Conservation Commission

Alaska Department of Administration, Alaska Oil and Gas Conservation Commission
Administration >  AOGCC >  Statistical Reports >  Current Oil & Gas Pools Statistics >  Prudhoe Bay Unit, Polaris Oil Pool
AOGCC Pool Statistics
Prudhoe Bay Unit, Polaris Oil Pool
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Operator: BP Exploration (Alaska) Inc. Index Map
Discovery Well: BP Exploration (Alaska) Inc.
  North Kuparuk State 26-12-12
  Permit #169-057
  API No. 50-029-20032-00-00
  Sec. 26, T12N, R12E, UM

Depth: 10,311 MD / 10,311' TVD

August 24, 1969

Status: Producing
Location: Central Arctic Slope Area Location Map Unit Location Map DNR Unit Map
Orders: List of Orders Summary - Annotated References  
Summary:

The Polaris Oil Pool is located within the western portion of the Prudhoe Bay Unit (“PBU“). It lies within the Late Cretaceous-aged Schrader Bluff Formation ("Schrader Bluff") and the Early Tertiary-aged Ugnu Formation (“Ugnu”). This pool is an accumulation of hydrocarbons common to and correlating with the interval between 5,544’ and 6,012’ measured depths in the Prudhoe Bay Unit S-200PB1 well. The pool has been producing continuously since November 1999 from the PBU W-Pad and S-Pads. Between November 1999 and December 2001, production averaged 1,110 barrels of oil per day (BOPD), with W-Pad contributing 700 BOPD (62%). Since January 2002, W-Pad has continued to dominate production. During the first six months of 2011, oil production from the pool averaged about 5,300 barrels per day. Of that, W-Pad produced an average of 4,540 BOPD (86%) and S-Pad averaged about 760 BOPD (14%).

Geology:

The pool encompasses reservoirs assigned to the Late Cretaceous-aged Schrader Bluff Formation and the Early Tertiary-aged Ugnu Formation. The Schrader Bluff was deposited in a marine shoreface and shallow shelf environment, and it is divided into two stratigraphic intervals that are designated, from deepest to shallowest, the “O-Sands” and the “N-Sands.” The O-Sands vary in thickness from 215’ to 320’, and the N-Sands vary from 95’ to 165’ thick. The overlying Ugnu reservoir intervals, informally termed the “M-Sands,” were deposited in deltaic and fluvial environments. The M-Sands vary in thickness from 180’ to 250’. The pool lies between approximately 4,800’ and 5,300’ feet true vertical depth subsea.

The Polaris structure dips gently to the east and northeast, and it is broken into a series of reservoir compartments by three sets of normal faults: one trending NW, the second trending N, and the third trending W. The NW- and N-trending faults range in vertical displacement up to 200 feet; they are the primary controls for oil distribution in the PBU W-Pad, S-Pad and M-Pad areas. The W-trending faults range up to 100’ in vertical displacement, and they trap oil in the center and along the southern margin of the pool, near the Term Well C, and near PBU N-Pad.

Oil distribution within the pool is complex: within the O- and N-Sands, ten oil-bearing intervals are recognized, and oil-water contacts appear to vary in depth. In the M-Sands, oil-water contacts are concentrated in the crestal portions of the structure, but they appear to vary in depth within different M-Sands suggesting that each behaves as a separate reservoir unit. The primary reservoirs of the pool lie in the O-Sands, and secondary accumulations occur in the N-Sands. API oil gravities range from 17 to 26 degrees. The M-Sands contain significant reserves, but the oil is biodegraded and viscous, with API gravity ranging from 12 to 14 degrees. The oil is under-saturated; there are no indications of a free gas column in the pool. At 5,500' true vertical depth subsea, the reservoir temperature is about 98 degrees F.

Strat Column Type Log
 
Production: Prod Chart    

  Oil (bbls) NGL (bbls) Gas (mcf) Water (bbls)
Cumulative 11,273,530 0 11,200,841 2,943,203
2005 Total
1,247,578 0 1,279,613 993,563
2006 Total
821,784 0 852,120 247,675
2007 Total
918,668 0 942,821 267,061
2008 Total
1,739,076 0 1,900,633 268,588
2009 Total
1,406,879 0 956,552 336,651
2010 Total
1,600,978 0 1,182,351 301,964
2011 Total
0 0 0 0
2007 Rate (b/d)
2,517 0 2,583 732
2008 Rate (b/d)
4,765 0 5,207 736
2009 Rate (b/d)
3,854 0 2,621 922
2010 Rate (b/d)
4,386 0 3,239 827
2011 Rate (b/d) 0 0 0 0
2008 Change (%)
89 0 102 1
2009 Change (%)
-19 0 -50 25
2010 Change (%)
14 0 24 -10
2011 Change (%)
0 0 0 0

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