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Alaska Oil and Gas Conservation Commission

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AOGCC Pool Statistics

Oooguruk Unit, Torok Oil

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Operator: Pioneer Natural Resources Alaska, Inc.
Index Map
Discovery Well: Pioneer Natural Resources Alaska, Inc.
  Oooguruk ODST-45A
  Permit No. 209-079
  API No. 50-703-20557-00-00
  Sec. 11, T13N, R07E, UM

Depth: 15,429’ MD / 5,018' TVD

October 30, 2009

Status: Producing
Location: Beaufort Sea Area Location Map Pool Location Map DNR Unit Map
Orders: List of Orders Summary - Annotated References  
Summary:

The Oooguruk-Torok Oil Pool lies offshore in the Beaufort Sea and onshore in the Colville River Delta, within the Oooguruk Unit on lands leased from the State of Alaska by the two working interest owners Pioneer (70%) and Eni (30%). The Oooguruk-Torok Oil Pool is the accumulation of hydrocarbons common to, and correlating with, the interval between the measured depths of 4,991 and 5,272 feet on the resistivity well log recorded in the Kalubik No. 1 exploratory well. The pool is being developed from the offshore Oooguruk Drill Site, which connects to the onshore Oooguruk Tie-in Pad, and then to the Kuparuk River Unit processing facilities.

The pool was discovered in 1986 by Texaco Inc.’s Colville Delta No. 2 and No. 3 exploratory wells, but tests of these wells achieved only very low flow rates from the Torok (less than 3 barrels per hour). Subsequent fracture stimulation of the lower portion of the Torok in Colville Delta No. 3 resulted in an average flow rate of 240 barrels of per day of crude oil and diesel mixture during two flow periods that totaled 84 hours.

In March 2010, Pioneer fracture-stimulated a 3,800 foot-long Oooguruk-Torok interval within horizontal well ODST-45A and began regular production. A three-well pilot program involving ODST-45A and two other horizontal wells is planned to further refine reservoir property estimates. The pool is currently producing from two wells, ODST-45A and ODST-46. During the third quarter of 2011, the pool averaged 526 barrels of oil per day with a 21% water cut. On June 24, 2011, the Alaska DNR, Division of Oil and Gas (AK DOG) approved the Oooguruk Unit Torok Participating Area, and on August 31, 2011, AK DOG approved the second expansion of the Oooguruk Unit to include acreage that contains the southern portion of the Oooguruk-Torok Oil Pool.

Geology:

The structure of the Oooguruk-Torok Oil Pool forms broad, east-plunging anticlinal nose cut by several, northwest- and north-trending, normal faults with vertical displacements ranging up to 40 feet. The top of the pool lies between about -4,800 true vertical depth subsea (TVDSS) and -5,500 feet TVDSS. The vertical displacement of faults observed within the Torok interval ranges up to 40 feet. Because of the thinly bedded nature of this reservoir, some faults may act as barriers.

The early Cretaceous-aged reservoir sandstones comprising the Oooguruk-Torok Oil Pool are typically very fine sand-sized to coarse silt-sized and rich in quartz (20% to 50%), feldspar (15% to 25%), and clay (5% to 40%), with metamorphic rock fragments and minor amounts of carbonate. These sandstones are sheet-like in form, and were deposited in a lower slope-to-basin floor environment. Within the proposed development area, the reservoir interval is 200 to 250 feet thick, but thins to the east, toward the paleo-basin, and pinches out to the west against the paleo-shelf slope. Net-to-gross sand thickness is typically 45% to 50%. Porosity ranges from 12% to 26%, averaging 19%. Permeability ranges from 0.1 to 100 millidarcies and averages 4 millidarcies. Water saturation estimates for the reservoir sandstones range from 40% to 55%, with an average of about 50%.

Well log and seismic information indicate that the Oooguruk-Torok oil accumulation is trapped by both structural and stratigraphic elements. The reservoir sandstones thin toward the west, and pinch out as they lap onto the toe of the paleo-slope. To the south and southwest, the depositional limit of the fan defines the pool boundary. To the north and east, structural dip, diminishing sand content in the sediments, and a southeast-trending, down-to-the-east fault appear to define the northeastern limit of the oil accumulation. The top seal for the pool is formed by more than 1,000 true vertical feet of shale and siltstone assigned to the undifferentiated Seabee Formation / Hue Shale.

The Colville Delta No. 3 exploratory well tested oil down to -5,150 feet TVDSS; the pool outline on the accompanying illustrations is based on this depth. The highest known water for the pool is established by MDT measurements in the Ivik No. 1 exploratory well at -5,212 feet TVDSS. The API gravity of Torok oil measures 24°, and viscosity ranges from about 2 to 4 centipoise. The solution gas-oil ratio (GOR) is estimated to be 250 to 550 standard cubic feet per stock tank barrel, and the bubble point pressure is estimated between 1,000 psig to 2,200 psig. Initial reservoir pressure is 2,250 psi at a depth of -5,000 feet TVDSS. Reservoir temperature is about 135° F. The oil formation volume factor is estimated from 1.15 to 1.30 reservoir barrels per stock tank barrel of oil, and the gas formation volume factor is estimated at 1.234 reservoir barrels per thousand standard cubic feet of gas. Free gas has not been encountered with the Torok interval.

  Strat Column Type Log
Production: Prod Chart          
  Oil (bbls) NGL (bbls) Gas (mcf) Water (bbls)
Cumulative 305,513 0 501,589 88,968
2010 Total
135,147 0 35,916 32,889
2011 Total
170,366 0 465,673 56,079
2010 Rate (b/d)
370 0 98 90
2011 Rate (b/d) 467 0 1,276 154
2010 Change (%)
100 0 100 100
2011 Change (%)
26 0 1202 71

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