Plato Viking Pool - Reservoir Engineering And Geological Study
Authors: Gillard D.R. , White W.I. 
Published: March 2010

The Plato Viking Pool is located 40 miles southwest of the town of Kindersley. Saskatchewan. Of approximately seventy wells drilled to date, fifty have been classified as oil producers.

The Plato reservoir comprises two distinct sand layers, the upper layer identified as the "A" sand and the lower layer as the "R" sand. The two sand layers are separated by 10 to 15 feet of shale. It was concluded that the "A" sand is the main oil-bearing section of the reservoir, with the possible contribution of the "B" sand very much in question at this time.

Ultimate recovery under primary depletion is estimated to be 2.4 million stock tank barrels, equivalent to 12.8 per cent of oil-in-place in the "A"sand.

Because of severe pressure depletion caused by the undersaturated state of the reservoir, it is recommended that waterflood operations begin at an early date. Ultimate recovery under waterflood is estimated to be in the order of 4.8 to 6.2 million stock tank barrels, with the most likely value approaching 6.2 million barrels. If field tests prove it feasible to waterflood the "B" sand in addition to the "A" sand, the expected waterflood recovery could be exceeded.

INTRODUCTION

THE PLATO VIKING POOL, located 40 miles southwest of the town of Kindersley, Saskatchewan, was discovered in March, 1967. Figure 1 sets the location of the pool relative to other commercial production of gas and oil in the general Kindersley area.· The discovery well was Houston et at Plato 4-7-25-17. It is interesting to note how this oil accumulation eluded the drill until the discovery date. During the two-year period 1954–1955, six wells were drilled and abandoned in the immediate vicinity. They form an envelope around the pool as it exists today. The discovery of oil at Plato, which is far removed from other oil reservoirs, has opened up a much greater area to further exploration in this part of the province.

Since the discovery, rapid development has continued and at the present time there are over fifty wells within the boundaries of the designated Plato pool. Drilling is on 80-acre spacing to depths of 2,050 to 2,450 feet, depending on location.

The Plato reservoir is highly undersaturated. This was first evident from a bubble-point determination of a subsurface sample and later confirmed by the first pressure survey, conducted in June, 1969. Confronted with the facts of severe pressure depletion and a corresponding rapid decline in productivity, it was necessary to consider plans for pressure maintenance.

This study describes the geology of the Viking Formation in an area including and contiguous with the Plato Pool. The effective hydrocarbon volume is defined and ultimate reserves under primary and waterflood operations are calculated.

GEOLOGY

The Viking Formation of Saskatchewan is a clastic assemblage, characterized by alternating beds of shale, siltstone and sandstone which underlies a large proportion of the province's sedimentary belt. Although local variations abound, the Viking Formation exhibits regional attenuation in a general northeasterly direction and gentle regional dip in a general southeasterly direction.