David1,2 is located outside of Lloydminster, Alberta in Canada.It produces from the Lloydminster sandstone at a depth of 2,490 ft and is currently operated by Husky Energy.The sandstone has an average porosity of 29% and an average permeability of 1,400 mD.The 22.6o API gravity crude oil has a viscosity of 34.1 cp at the reservoir temperature of 87oF.The portion of the field affected by alkali-polymer has a pore volume of 12,462 Mbbls with an original oil in place of 9,347 Mbbls or 75% oil saturation.The figure to the left shows the net pay isopach.The majority of the pool was AP flooded while sections to the north, west, and south were only waterflooded.Primary production from 1969 to 1978 was 532 Mbbls of oil or 5.7% OOIP.Waterflood production from 1978 to the middle of 1986 was 1,700 Mbbls of oil or 18.2% OOIP, for a total primary plus waterflood oil recovery of 23.9% OOIP.The ultimate primary plus waterflood recovery was predicted by the operator to be approximately 52% OOIP.The production performance of the AP flood area production performance is shown in the first figure below.The north, west and south areas of the David Pool proved that the 52% OOIP prediction for the waterflood is valid.The middle figure below shows that the oil recovery of the three waterflood areas is approximately 52% OOIP at a 2% oil cut.
In 1985, Dome Petroleum performed a laboratory study to define a chemical system to improve the waterflood performance.A series of fluid-fluid and coreflood evaluations determined that the most economical chemical flood technology to apply was an AP flood.The figure above on the right shows the radial coreflood performances of an AP flood compared with an ASP flood.An initial evaluation of the radial corefloods results suggests that an ASP flood will outperform an AP flood.However, when the better waterflood performance is taken into account, the additional 2.9% OOIP incremental oil due to the addition of surfactant to the alkaline-polymer solution is not sufficient to cover the surfactant cost.
Alkali plus polymer injection was initiated in the David Field during June 1987.The project has an irregular pattern consisting of 7 injection wells and 18 production wells on 20 acre spacing.The injection sequence was 0.21 pore volume of 1.0 wt% sodium carbonate plus 800 mg/L Alcoflood 1175A followed by 0.04 pore volume of a tapered Alcoflood 1175A slug.The water drive subsequent to the tapered polymer drive began in December 1990.Alkali plus polymer injection was predicted to recover 18% OOIP or 1,800 Mbbls of oil for a cumulative ultimate predicted oil recovery of 70% OOIP.As of January 1, 2002 a total 6,850 Mbbls of oil or 73.3% OOIP have been produced by primary, waterflood, and chemical flood.The first two figures above show the production.The ultimate performance results in an incremental recovery of 2,010 Mbbls or 20.0% OOIP due to the AP injection.Chemical, plant and operations cost per incremental barrel are US$0.99.
1 Manji, K.H. and Stasiuk, B.W.: "Design Considerations for Dome's David Alkali/Polymer Flood," Can. J. Pet. Tech., 1988, vol 27, pages 49-54.
2 Pitts, M.J. Wyatt, K., and Surkalo, H: "Alkaline-Polymer Flooding of the David Pool, Lloydminster Alberta", SPE 89386, Fourteenth Symposium on Improved Oil Recovery, April 2004.
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