The Harmattan East Rundle oil and associated gas-cap accumulation iscontained in a stratigraphic trap limited downdip on the oil leg by anerosional channel and updip in the gas cap by truncation of the Turner Valleyformation of the Rundle group. A total of 178 million barrels of stock tank oiland 1,100 Bcf of associated gas-cap gas were estimated to be originally inplace. The gas cap is shut-in pending reasonable depletion of the oil column. Agas-cap cycling scheme was engineered to increase and accelerate recovery ofgas-cap liquids and to partially maintain oil-column pressure during cycling. Anumerical solution to the differential equation for two-dimensional horizontalsteady-state flow was used to determine the location, production and injectionrates for each well in the cycling scheme. The expanded material balance, unsteady-state flow and gas displacement equations were combined for predictingthe performance of this combination-drive reservoir.
The Harmattan East reservoir, discovered in 1956, is located approximately50 miles north-northwest of the city of Calgary (Figure1), in theProvince of Alberta. Oil production is obtained from the Mississippian TurnerValley formation at an average depth of 8,500 feet. The Turner Valley erosionalremnant is underlain by impermeable shales and sandstones of Jurassic andCretaceous age. Reservoir development within this formation occurs in zones ofporous dolomite with associated beds of dense limestone.
The east, south and west productive limits of the field have been fairlywell established. The northern limit, however, has yet to be defined.Development of the oil column is nearly complete and, as of January 1, 1963, there were ninety producing oil wells on 80-acre spacing. Gas-cap developmenthas resulted in sixteen gas-condensate wells. In December of 1961, a scheme forconserving casinghead gas was initiated.
