DETAILED EVALUATION OF THE WEST KIEHL ALKALINE-SURFACTANT-POLYMER FIELD PROJECT AND ITS APPLICATION TO MATURE MJNNELUSA WATERFLOODS

The combination of an interfacial tension agent and a mobility control agent has the potential to produce additional oil beyond a waterflood. The West Kiehl alkaline-surfactant-polymer project is the first application of this chemical enhanced oil recovery technique. The West Kiehl alkaline surfactant- polymer flood was initiated in September 1987 as a secondary application after primary recovery. The following analysis of the West Kiehl alkaline-surfactant-polymer flood indicates that incremental oil greater than waterflooding was produced at a cost of less than $2.00 per incremental barrel. A analysis of approximately 120 Minnelusa oil fields in the Powder River Basin indicates that the total original stock tank oil in place exceeds one billion barrels. If the enhanced oil recovery technology implemented at West Kiehl field could be successfully applied to these fields, the potential incremental oil recovery would approach 130 million barrels. The goals of "Detailed Evaluation of the West Kiehl Alkaline-Surfactant-Polymer Field Project and It's Application to Mature Minnelusa Waterfloods" are to evaluate both the field performance of the alkaline-surfactant-polymer enhanced oil recovery technology as well as its potential application to other Minnelusa oil fields. The objectives of the project are: - Evaluate the geological depositional environment of the West Kiehl and of adjacent Minnelusa sand reservoirs with similar fluid and rock characteristics. -Those reservoir analogs with depositional environments similar to the West Kiehl field will be compared on an engineering basis to define both geological and reservoir performance analogs to the West Kiehl field. - Compare the production performance results of the best geological and reservoir performance analogs to the West Kiehl field and select two fields for in-depth study. Polymer floods and waterfloods performances were defined. - Compare the two best field analogs to the West Kiehl field using numerical simulation. - History match the results of the laboratory radial coreflood physical simulation the West Kiehl field - History match the actual field performance of the alkaline-surfactantpolymer flood at West Kiehl field - Forecast the future performance of the West Kiehl project and determine the incremental oil recovery greater than waterflooding - History match the actual field performance of the waterflood analog  - History match the actual field performance of the polymer flood analog - Predict the results of applying the alkaline-surfactant-polymer technology as a tertiary oil recovery technology on the two mature Minnelusa waterflood analog units using classical engineering and numerical simulation. -Predict the waterflood and polymer flood performance of the West Kiehl field using numerical simulation and the parameters established in the analog field numerical simulations. Linear and radial coreflood oil recovery by water injection was 56.3% OOIP and 46.6% OOIP, respectively, leaving a waterflood residual oil saturation of 0.343 PV. Injection of alkali plus surfactant plus polymer into the linear corefloods produced an additional 17.3% OOIP for a cumulative oil recovery of73.7% OOIP with a final residual oil saturation of 0.207 PV. Radial coreflood alkaline-surfactant-polymer oil recovery averaged 61.7% OOIP. Numerical simulation of the West Kiehl projects the ultimate recovery to be 1,017,000 barrels of oil from alkaline-surfactant-polymer injection and 726,000 barrels from a waterflood. Net incremental oil is 291,000 barrels. This compares with 249,200 to 309,260 barrels  of incremental oil by classical reservoir engineering methods. A mobility control polymer flood will produce 885,000 barrels of oil and alkali-surfactant injection will produce 850,000 barrels of oil. Interfacial tension agent (alkali and surfactant) and mobility control agent (polymer) contributions to the total alkaline-surfactant-polymer incremental oil appear to be additive. After studying 72 fields in a 275 square mile area around the West Kiehl, Prairie Creek South and Simpson Ranch were selected as waterflood and polymer flood analogs. Prairie Creek South numerical simulation predictions of the waterflood is 790,000 barrels of oil or 39.4% OOIP. Classical engineering prediction for the ultimate waterflood recovery is 764,900 to 814,900 barrels of oil or 38.1 to 40.6% OOIP. Alkaline-surfactant-polymer injection is predicted to produce 1,100,000 barrels for 310,000 barrels of incremental oil. A mobility control polymer flood estimated recovery is 919,000 barrels of oil. Simpson Ranch classical reservoir engineering analysis indicates the Cat-An? polymer flood will ultimately produce 867,000 to 920,000 barrels of oil or 38.0 to 40.3% OOIP compared to 831,000 predicted by numerical simulation. Numerical simulation predictions for a waterflood and an alkaline-surfactant-polymer flood indicates ultimate oil recovery to be 745,000 and 1,095,000 barrels oil, respectively. Incremental oil for a Cat-An? polymer flood is 86,000 and for an alkaline-surfactant-polymer flood is 350,000 barrels of oil. If an alkaline-surfactant-polymer project was implemented after a waterflood in the West Kiehl, Simpson Ranch and Prairie Creek South fields the incremental oil recovery predicted by the numerical simulator is 321,000,323,000, and 272,000 barrels, respectively. The West Kiehl total production by alkaline-surfactant-polymer flood forecast was greater after a waterflood because the Kottabra 25-15 well was on production for the entire alkaline-surfactant-polymer injection period, rather than 6 months.

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