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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
Colville River Unit, Fiord Oil Pool
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Operator: ConocoPhillips Alaska, Inc. Index Map
Discovery Well: ARCO Alaska Inc.
  Fiord 1
  Permit #191-147
  API No. 50-103-20162-00-00
  Sec. 2, T12N, R05E UM

Depth: 10,250 MD / 9,973' TVD

April 18, 1992

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

Oil-stained sand currently assigned to the Fiord Oil Pool was first encountered in the Nechelik No. 1 exploratory well in 1982. However, the Fiord No. 1 exploratory well is considered to be the discovery well as it tested oil at an average rate of 1,065 barrels per day from the upper portion of this pool and 180 barrels per day from the lower portion of the pool. This discovery was confirmed by Fiord No.2 in 1994, and then delineated by the Fiord No.4, Fiord No.5, Nigliq No.1, and Nigliq No. 1A wells that were drilled between 1999 and 2001.

 

The Fiord Oil Pool is common to, and correlative with, the interval between the measured depths of 6,876' and 7,172' in the Fiord No. 5 well. This pool is unusual in that it encompasses two sandstone reservoir intervals that are in direct contact and in hydraulic communication within the oil column. The deeper reservoir interval, informally termed the "Nechelik zone," is Jurassic-aged (Oxfordian) and lies within the Kingak Formation. The shallower reservoir interval, informally named the "Kuparuk zone," lies within the Cretaceous-aged (Hauterivian) Kuparuk Formation.

 

Regular production began from the pool in early August 2006, and with the addition of new wells, production reached 24,355 barrels of oil per day (BOPD) in June 2007, 26,325 BOPD in May 2009, and peaked at 32,906 BOPD in April 2010. For the first six months of 2011, the pool has averaged 20,452 BOPD.

 

Geology:

The Fiord Oil Pool consists of three intervals. They are, in ascending order, the Nechelik, an intervening wedge of non-reservoir shale and sandstone, and the Kuparuk.

 

The Nechelik interval consists of fine-grained, quartz-rich, sandstone that was deposited in environments ranging from marine-shelf (at the base of the zone) to middle shoreface (near the top). Detrital matrix constitutes 10 to 30 percent of the sediments at the base of the Nechelik, but decreases in abundance upwards as sand content increases. The best-quality reservoir sandstone occurs near the top of the zone. Detrital matrix is predominantly mixed-layer illite/smectite, discrete illite and kaolinite clays with some localized siderite cement. Clay swelling is not expected to be significant based on core flood studies and experience with similar clays in the Alpine Field. Nechelik porosity averages about 16%, and air permeability averages approximately 8 millidarcies. Average water saturation is about 34% in the Fiord No.4 and Fiord No.5 wells.

 

Between the Nechelik and Kuparuk intervals is a wedge of non-reservoir shale and sandstone that thickens to the south. The top of the non-reservoir wedge is the Lower Cretaceous Unconformity ("LCU"), which at one time was a regional erosional surface. In the northern and northwest part of the development area, the LCU dips to the north and cuts down into the Nechelik zone, and the reservoir sand of the Kuparuk zone directly contacts reservoir sandstone of the Nechelik zone. The base of the wedge is the top of the Nechelik zone, which dips southeast within the proposed development area. Along the southeastern edge of the affected area, within portions of Sections 13, 14, and 15 of TI2N, R5E, UM, the wedge of sediments separating the Nechelik and Kuparuk zones contains a thin interval of Alpine sandstone. This sandstone is 5' thick in the Fiord No.2 exploration well, where it was described as being fine-to medium-grained, calcareous, and glauconitic with spotty, medium to dark brown oil staining. In this area, which is situated more than 2 miles from the nearest Alpine development well, the Alpine sandstone appears to be of fair to poor reservoir quality.

 

The Kuparuk interval consists of a transgressive, shallow-marine lag deposit that is situated directly atop the LCU and is typically less than 5' thick. It consists of fine- to medium-grained, quartz-rich sandstone containing varying amounts of glauconite and siderite cement. Initial drilling results indicate the Kuparuk sandstone thickens locally on the western (downthrown) side of northwest-trending normal faults that occur in the development area. Kuparuk zone porosity averages about 22%, and air permeability averages approximately 110 millidarcies. Average water saturation is about 22% in the Fiord No.5 well.

 

Within the Fiord development area, the structure at Kuparuk level dips to the northwest. During early Cretaceous time, faults were active creating accommodation space for accumulation of sediments. The main fault in the development area is termed the "Fiord" fault. Therefore, as stated above the Kuparuk reservoir is thickest on the downthrown, western side of this northwest-trending normal fault, and it thins toward the west.

 

Well log and seismic information indicates that the oil in the pool is trapped by both structural and stratigraphic elements. The trapping mechanisms for oil within the Kuparuk reservoir are the Fiord Fault to the east and stratigraphic pinch-outs into very fine-grained, non-reservoir rock in all other directions. The Nechelik reservoir is truncated by the LCU to the north, and it degrades to non-reservoir quality to the south and west.

 

Geochemical analyses of reservoir fluids recovered from well tests of Fiord No.5 and RFT tests of Fiord No.4 indicate that oils trapped within the Nechelik and Kuparuk zones are likely the same oil. Oil viscosity ranges from 0.79 to 0.92 centipoise, solution-gas ratio ranges from 538 to 609 standard cubic feet per stock tank barrel, and the formation volume factor ranges from 1.299 to 1.333 reservoir barrels per stock tank barrel. Crude oil produced during testing measured between 28.6 and 31.3 degrees API gravity. Neither gas-oil nor oil-water contacts have been observed within the Nechelik and Kuparuk zones within the proposed pool area. Original Nechelik zone pressure is approximately 3,200 psi at 6,900' true vertical depth subsea ("TVDSS"). Reservoir temperature is approximately 163°F at 6,850' TVDSS. (Conservation Order 569)

  Strat Column Type Log
Production: Prod Chart    
  Oil (bbls) NGL (bbls) Gas (mcf) Water (bbls)
Cumulative 39,633,078
0 30,784,227 7,571,281
2005 Total
15,570 0 0 0
2006 Total
1,757,212 0 1,128,132 5,790
2007 Total
5,564,435 0 4,530,628 594,370
2008 Total
6,666,944 0 4,301,216 324,985
2009 Total
8,435,295 0 6,408,535 523,643
2010 Total
9,431,181 0 8,500,732 2,330,067
2011 Total
7,735,994 0 7,043,116 3,798,216
2007 Rate (b/d)
15,245 0 9,367 1,613
2008 Rate (b/d)e
18,266 0 11,784 890
2009 Rate (b/d)
23,110 0 17,558 1,435
2010 Rate (b/d)
25,839 0 23,290 6,384
2011 Rate (b/d) 21,195 0 19,296 10,406
2008 Change (%)
20 0 26 -45
2009 Change (%)
27 0 49 61
2010 Change (%)
12 0 33 345
2011 Change (%)
-18 0 -17 63
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