Reservoir Characterization and Simulation of the Kisbey Frobisher-Alida Pool in Southeast Saskatchewan

Abstract The Kisbey Frobisher-Alida pool, located in southeast Saskatchewan, was discovered in 1985. The pool consists of multi-layer complex geology, with the Kisbey Sand sandwiched between two carbonate layers, the Frobisher and Alida beds. The pool has been producing under primary depletion drive, with a weak natural edge aquifer as the dominant drive mechanism. Some areas of the pool are experiencing low reservoir pressure, suggesting limited connectivity between the aquifer and those areas of the pool. The lowest pressure is observed in an up-dip area of the pool. A detailed study was launched in November 2001, beginning with a reservoir characterization and evaluation analysis. This process included developing a new geological model, verified with 3D seismic data. The reservoir characterization work was difficult because of multi-layering effects, limited reservoir pressure data, aquifer effects, and lower reservoir quality overall. A computer simulation was undertaken to study the feasibility of a waterflood in lowpressure areas of the pool and to examine the effect of the waterflood on the overall recovery from the pool. The study confirmed the need for pressure support. This proposal is somewhat unique because it recommends a waterflood to a partial water drive system. The recommended depletion scenario is in the process of being implemented, following the recent unitization of the pool. Some factors, including the degree of heterogeneity and exact locations of permeability barriers, remain to be verified by observing the pool's response to waterflooding. Adjustments to the pool's depletion strategy may be required in the future, based on these factors. Introduction The Kisbey Frobisher-Alida pool is a complex reservoir situated near the town of Kisbey, roughly 75 km east of Weyburn, Saskatchewan in TWP 8–6 W2. It was discovered by Canadian Hunter in 1985 and was developed rapidly thereafter. The pool consists of three stacked, but isolated, reservoir units: the Alida Limestone, the Kisbey Sandstone, and the Frobisher Limestone. As at March 2004, the pool has produced 1.46 106 m3 (9.18 MMbbl) of oil (as shown in Figure 1). This paper outlines the study prepared by Northrock Resources, Epic Consulting, and Cuesta Energy Inc. of the Kisbey Frobisher-Alida pool. Initiated in November 2001, the purpose of this study was to determine whether waterflood potential existed in the pool and to identify how best to implement the waterflood. A new geological model was postulated and confirmed with 3D seismic. In addition to the Kisbey channels between Alida highs model (discussed in detail in the geological section), another change in interpretation involves the segregation of the three reservoir units. This interpretation was confirmed by the model, but is also supported by geological, production, and pressure data. The new interpretation of the reservoir was used to generate a 3D computer simulation of the pool. The simulation model provided insights into how the field was performing and how best to implement a waterflood. The study provided recommendations for both injection and further horizontal producers in the Kisbey Sand. Despite having completed a detailed review of the pool, there are still questions about ultimate recovery, uncertainties in the study, and future potential exploitation opportunities to explore.