The Cambridge Minnelusa field alkaline-surfactant-polymer ͑ASP͒ flood was an economic and technical success, with ultimate incremental oil of 1,143,000 bbl at a cost of $2.42 per barrel. This success was due to an integrated approach of the application, including: reservoir engineering and geologic studies, laboratory chemical system design, numerical simulation, facilities design, and ongoing monitoring. This paper discusses how each of these was used in the design and evaluation of the Cambridge ASP project.

The West Kiehl Unit, Crook County, Wyoming produces from the Minnelusa Lower "B" Sand reservoir. Original oil in place (OOlP) is estimated at 238,481 m 3 . Estimated ultimate primary production is 27,028 m 3 or 11% OOlP. Four enhanced oil recovery methods were considered for application in this reservoir: conventional waterflood, polymer flood, an alkaline-polymer flood, and an alkalinesurfactant-polymer (ASP) flood.Estimated ultimate recoveries are 95,392 m 3 (40% OOlP), 95,392 m 3 (40% OOlP), 95,392 m 3 (40% OOlP), and 135,934 m 3 (56% OOIP), respectively. The polymer flood is expected to deplete the field faster than a conventional waterflood without an increase in ultimate recovery, while the ASP technology is expected to extend the field life and increase ultimate recovery dramatically. The ASP process has been implemented and early performance is very good.Two purposes are being served by implementation of the West Kiehl alkaline-surfactant-polymer flood. The rust is to recover additional oil not recoverable by a waterflood or a polymer flood. The second is to pilot this potentially significant enhanced oil recovery (EOR) technique for other Minnelusa reservoirs. If this method proves successful, it will represent a sizable increase in ultimate recovery with the incremental oil recovery ranging as high as 25% OOIP. This paper discusses the goal for utilizing the alkalinesurfactant-polymer technology at the West Kiehl. Further, it details the development of the West Kiehl Field project including laboratory studies, reservoir parameters, initial injection and production history, facilities design, and operations of the flood.

An alkaline-surfactant-polymer flood was initiated in September 1987 in the Minnelusa Lower "B" sand at the West Kiehl Unit. Subsequent to unitization, two producing wells were drilled outside the Unit boundary. While this extended the productive geologic interpretation of the field, it did not effect the Unit interpretation of the alkaline-surfactant-polymer flood. Production from primary and chemical injection into State 31-36 through November 1991 resulted in 517,521 barrels of oil (82,279 m3) from the Unit wells, of which 456,361 barrels (72,555 m3) were from the area swept by injection into State 31-36. The two Kottraba wells (north of the Unit) have produced 180,686 barrels of oil (28,727 m3) as of November 1991. The- original average oil saturation in the gross swept area was 71.8% PV (69.0% PV in stock tank barrels). The gross swept pore volume of the Unit is 1,294,800 barrels (205,857 m3). The oil recovery efficiency in the gross swept area as of November 1991 is 51.1% OOIP. Projected ultimate production from the gross swept area is 541,158 barrels of oil (86,037 m3)- or 60.6% OOIP. Projected ultimate production from the Unit is 602,318 barrels of oil (95,761 m3). This compares with a primary plus waterflood oil recovery estimate of 39.9% OOIP recovery for the West Kiehl Unit gross swept area. Comparison of the oil recovery efficiency of the West Kiehl with other Minnelusa waterfloods and polymer floods suggests the West Kiehl has out performed these other Minnelusa floods. Using the Slider technique, the displacement efficiencies of the areas swept by the State 32-36 and State 42-36 in the Unit and Kottraba Federal 2515 were 71.3%, 52.7% and 58.1%, respectively. Comparative efficiency factors for a waterflood in the Hamm Unit and a polymer flood in the OK Field are 28.5% and 45.6%. The West Kiehl, OK Field, and Hamm Unit are all Lower "B" Minnelusa Fields. A total of 184,794 incremental barrels of oil (29,380 m3) are projected for the Unit at an incremental cost of $393,458- or $2.13 per incremental barrel of oil ($13.40 per m3). No injected chemical production has been observed in the Unit wells- or the Kottraba wells as of November 1991. No changes in the Hall plot slopes were observed once a stable slope was achieved until water break through occurred at State 32-36. Alkali plus surfactant plus polymer was injected without damage to the Minnelusa formation.

Summary A tertiary pilot application of the Alkaline-Surfactant-Polymer (ASP) process was initiated in September, 1994 in West Center Area of Daqing Oil Field. The pilot pattern consists of 4 inverted five-spot, including 4 injectors and 9 producers, as well as 2 observation wells encompassing an area of 90,000 m2 and with a pore volume of 203,300 m3. The target layer is Saertu II1-3 sandstone with average porosity of 26% and permeability of 1.426 m2. The crude oil viscosity is 11.5 mPa.S at reservoir temperature and the connate water salinity is 6,800 mg/L. The current pilot performance shows a pronounced response from Alkaline-Surfactant-Polymer injection. The average pilot area oil production rate increased from 36.7 m3/d to 91.5 m3/d, while water cut decreased from 82.7% to 59.7%. For the central well Po5, which is surrounded by injection wells, the oil production rate increased from 3.7 m3/d to 27.1 m3/d while water cut decreased from 87.9% to 45.8%. The numerical simulation results forecast that the oil recovery will be increased by 18.1% OOIP. Introduction The Daqing oil field is the largest field in the Peoples Republic of China. The pilot site is located on the west limb of the Saertu anticline. The reservoir slopes gently from east to west with an average depth of 814 m. The target layer in the pilot area, the Saertu II1-3 sandstone formation was deposited in a flood plain distributary environment. The sandbody is mainly composed of highly meandering distributary sandstone. The sandstone reservoir distribution is wide and thick, with high permeability and high inter-formational heterogeneity. The connate water salinity is relatively low, and fresh water is available. The reservoir characteristics, fluid properties, waterflood performance, and the performance of polymer flood pilot tests, indicated that the Daqing field was an ideal candidate for the Alkaline-Surfactant-Polymer process. Other papers have reported on ASP performance of field projects in the United States, but this paper reports on ASP effect at an advanced stage of waterflooding in the Daqing ASP pilot. History The Daqing field was discovered in 1959. Generalized water injection began in June of 1960 and separate layer injection began in January of 1965. The field was developed in a line drive pattern with rows of injectors 2,400 meters apart and spacing between wells within a row of 500 meters. Between rows of injectors are 3 rows of producing wells evenly spaced at 600 meters between rows. The oil production has been maintained at more than 160,000 m3/d since 1979 by this infill drilling and development resulting in more than 10,000 wells. Artificial lift development began in January of 1981 continuing until December of 1989. Beginning in 1984 the reservoir characteristics were screened for the application of enhanced oil recovery techniques. Two polymer flood pilots were performed beginning in 1987 with watercuts decreasing an average of 16% and oil rates increasing three-fold. These results indicated that mobility control polymer flooding could significantly improve oil recovery. As a result of these pilots, on-site polymer manufacturing facilities were built capable of producing 50,000 tons of polyacrylamide polymer per year. This facility began initial production in September of 1995. The Alkaline-Surfactant-Polymer process was identified as a means to further increase recovery and utilize the polymer made on site. The pilot area was originally developed beginning in December of 1987 for one of the polymer flood pilots. However, the polymer flood produced from intervals about 100 m deeper than the Alkaline-Surfactant-Polymer pilot. Fig. 1 shows the pilot area located between the well Zhong 5-8 and - Zhong 5-10 in the west central area of Daqing Field.

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