A polymer-flood pilot project in the Rapdan field is documented from laboratory design and numerical simulation to production performance and projected economics. The Rapdan field produces 10-mPa' s oil from the Upper Shaunavon sand at a reservoir temperature of 55°C. Average permeability is 0.1l4.um2, average porosity is 18%, and Dykstra-Parsons coefficient is 0.8. The field was discovered in 1953, and waterflood began in 1962. In Jan. 1986, a polymer pilot was initiated in a portion of the field with a PV of 456 x 1 Q4 m3. The pilot consists of 13 producers and 5 injectors drilled on 162 x J03-m2 spacing. By Dec. 1994, 43% PV of a 21-mPa' s polymer solution had been injected into a confined, central five spot (Wells 12-12 and 12-12A). The oil cut increased from a stable value of 8% during the waterflood to a peak value of 25%. The corresponding daily oil production increased from 8 to 28 m3/d. The performance of the total project oil production increased from 65 m3/d at an oil cut of 18% to a peak production of 180 m3/d at an oil cut of 36%. Production rate has declined from 140 m3/d in 1991 to 106 m3/d in Dec. 1994, with a corresponding oil-cut decline from 25% to 20%.
The Rapdan Unit is in the southwest comer of the province of Saskatchewan, Canada, =30 km from the Montana (U.S.) border. The Rapdan Unit was identified as a polymer-flood candidate because of its high mobility ratio. The oil viscosity of 10 mPa . s and water viscosity of 0.53 mPa' s results in an unfavorable mobility ratio of 4.5.