Pressure Maintenance By Waterflooding North Virden Scallion Field, Manitoba
Authors: Park R.A. 
Published: December 2007

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This paper was to be presented at the California Regional Meeting of the Society of Petroleum Engineers of AIME, to be held in Bakersfield, Calif., Nov. 4–5, 1965, and is considered to an abstract of not more than 300 words, with no illustrations, unless the paper is specifically released to the press by the Editor of the Journal of Petroleum Technology or the Executive Secretary. Such abstract elsewhere after publication in the Journal of Petroleum Technology or Society of Petroleum Engineers Journal is granted on request, providing proper credit is given that publication and the original presentation of the paper.
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Abstract
The North Virden Scallion field is located on the northeast flank of the Williston Basin and produces from the Virden and Scallion members of the Lodgepole formation of Mississippian age. The reservoir was highly undersaturated initially. The sources of energy for primary production were a combination of oil expansion, partial edge-water drive and limited bottomwater drive. Laboratory flooding tests and engineering calculations indicated that water flooding could more than double the anticipated primary recovery and significantly increase the rapidly declining production rates. It was estimated that the ultimate primary recovery of 25 million bbl could be increased to 55 million bbl.
After five years of planning and negotiating, a portion of the field was unitized and a nine-spot water flood was installed. Water injection began in Dec., 1962. Results to date have been encouraging. Production has increased from a pre-flood rate of 2,900 BOPD to 5,230 BOPD. Additional oil recovery due to water flooding is estimated to be over 900,000 bbl to June 30, 1965. To assist in predicting and controlling the advance of the flood fronts, injection profiles have been run on the injection wells and a digital computer model to simulate the project is currently being constructed.

Introduction
The North Virden Scallion field is located in southwest Manitoba, 30 miles east of the Saskatchewan border and due north of the town of Virden. This places the field approximately midway between Regina and Winnipeg. Production is obtained from the Virden and Scallion members of the Lodgepole formation of Mississippian age at a depth of 2,000 ft.
The field was discovered in Dec., 1953 by The California Standard Co. with the drilling of Calstan Scallion 3-11-11-26 W.P.M. Development followed rapidly and by 1961 over 300 wells had been drilled, of which 274 were capable of production. All wells were drilled on 40-acre spacing and placed on the pump soon after completion. Tn early 1957 the field's production rate and pressure were declining rapidly and the need for pressure maintenance had become obvious. Engineering and laboratory studies conducted that year showed that water flooding was the only economical method of secondary recovery.
After an attempt to initiate a pilot water flood failed in 1958, negotiations to unitize the field began. On Aug. 1, 1962, the North Virden Scallion Unit No. 1 became effective. The unit contained 217 wells completed in the Lodgepole formation. [See Fig. 1.] The remaining wells located on the down-dip southwest flank were not included because they were being effectively depleted by edge-water drive. Injectivity calculations indicated that an inverted 9-spot pattern would provide sufficient injectivity to more than maintain pressure. Pattern adjustments had to be made because of window tracts which were not in the unit. The injection systems were installed in two phases.