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Alaska Oil and Gas Conservation Commission

Alaska Department of Administration, Alaska Oil and Gas Conservation Commission
Administration >  AOGCC >  Statistical Reports >  Annual Pool Statistics - 2004 >  Endicott Unit, Endicott Oil Pool
AOGCC Pool Statistics
Endicott Unit, Endicott Oil Pool
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Operator: BP Exploration (Alaska) INC.

Discovery Well: Sohio
  Sag Delta 34633 No. 4
  Permit #177-015
  API No. 50-029-20245-00-00
  Sec. 35, T12N, R16E, UM

Depth: 12,855’ MD / 10,895' TVD

March 13, 1978

Status: Producing
Location: Central Arctic Slope Area Location Map Unit Location Map DNR Unit Map
Orders: Complete List
Summary:
The Endicott Oil Pool (“Endicott”) is located in the Beaufort Sea, about 8 miles east of Prudhoe Bay Unit (“PBU“). It was discoveredin 1978 by the Sohio Alaska Petroleum Company Sag Delta No. 4 well and confirmed in 1979 by Duck Island No. 1, which encountered 358’ of gross oil pay and 67’ of gross gas pay within the Kekiktuk Formation ("Kekiktuk"). This pool has been developed from two artificial, gravel islands that are located approximately 4 miles offshore in 2- to 14-feet of water. These islands connected by a 1-1/2 mile long gravel causeway. The northern portion of the pool is produced mainly from the Main Production Island (“MPI”), and the southern portion of the pool is produced mainly from the Satellite Development Island (“SDI”). Continuous production began in July 1986. During the peak production years from November 1987 and October 1993, Endicott averaged about 104,250 barrels of oil per day (“BOPD”). Between November 1993 and March 1995, production dropped to an average of 94,400 BOPD. From April 1995 to February 2001, production declined steadily at an average annual rate of about 18% (from 93,450 to 30,450 BOPD). From March 2001 and April 2004, oil production averaged approximately 25,000 BOPD, but during the last 8 months of 2004, production from Endicott declined to 17,600 BOPD. MPI has yielded approximately 59% of the oil recovered to date from this pool. The pool is developed on 40-acre spacing.

Geology:
The Endicott Oil Pool is defined as the accumulation of hydrocarbons common to and correlating with the interval between 11,496’ and 12,812’ measured depths in the Sag Delta No. 4 well. It occurs in Mississippian-aged, fluvial sediments. The pool is trapped by a combination of structural and stratigraphic elements within a large, northwest-southeast trending fault block that dips toward the northeast. Normal faults border the accumulation to the north and southwest. Structural dip limits the field to the southeast. Upper confinement for the accumulation is provided by the Kayak Shale-Itkilyariak Formation and, in the northeastern portion of the pool, by the Lower Cretaceous Unconformity. The pool is broken by several minor faults that are subparallel to the major bounding faults. One of these faults, termed the Mid-Field Fault, is sealing, and it divides the reservoir into two parts: a northern field area that is produced mainly from the Main Production Island (“MPI”), and a southern area, which is produced mainly from the Satellite Development Island (“SDI”). Three lithostratigraphic units are defined within the Kekiktuk Formation. They are, in ascending order, Zone 1, Zone 2 and Zone 3, and they have an aggregate thickness of up to 1,200’. Zone 1 consists mainly of the shale, coal and siltstone deposited in floodplain, swamp and lacustrine environments. Associated sand bodies have very limited continuity. Zone 2 contains very porous and permeable, laterally continuous, medium-grained reservoir sandstone primarily deposited in low-sinuosity, coalescing braided channels that extend across the entire reservoir. Associated, locally continuous shales within Zone 2 were deposited in lacustrine environments. Zone 3 consists of fine-to medium-grained sandstone occurring in stacked point-bar channels deposited in a high-sinuosity, fluvial environment. These stacked channel sands are lenticular, and are interspersed with equal amounts of shale, siltstone and coal, which accumulated in between the fluvial channels. A gas-oil contact occurs at about 9,855’ true vertical depth subsea (“TVDss”), and an oil-water contact occurs at approximately 10,190’ TVDss. The areal extent of the hydrocarbon accumulation is about 8,600 acres. During 1991, oil-in-place and gas-in place were estimated to be 1.1 billion barrels, 400 BCF of gas in the gas cap, and 800 BCF of gas in solution.

Structure Map Strat Column
Orig. Oil in Place: 1.1 Billion STB (CO 202 Testimony; Adamson and others, 1991)
Orig. Gas in Place: 400 Billion SCF gas-cap in place, 800 BCF solution gas  (Adamson and others, 1991)
Production: Prod Chart Prod Report Prod Data

  Oil (bbls) NGL (bbls) Gas (mcf) Water (bbls)
Cumulative 427,236,639
20,375,342 1,824,601,914 733,762,342
2001 Total 9,636,814 1,324,321 134,122,209 69,056,839
2002 Total 8,508,940 1,202,377 134,692,614 73,985,954
2003 Total 9,104,149
1,188,955 141,555,553 76,212,420
2004 Total 7,367,913 971,260 130,206,232 72,337,965
2003 Daily Rate 24,942 3,257 387,823 208,801
2004 Daily Rate 20,186 2,661 356,729 198,186
Change (%) -19% -18% -8% -5%

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