The first Nisku Formation discovery (Fig. 1) in the West Pembina area was made in January 1977 with the drilling of a seismic anomaly which was interpreted as an isolated reef. To early 1980, forty-five additional isolated reefs had been discovered in the West Pembina area.

The location of the area and the generalized regional geology is shown in Figure 1. The area is located on the eastern homocline of the Alberta Basin. Regional dip to the southwest is about 70 feet per mile. The block diagram (Fig. 2) illustrates the stratigraphic relationships of the West Pembina pinnacle reef area in the Winterburn Basin as it would appear with upper Nisku strata removed. The Nisku Formation in the West Pembina area is divided into five members (Fig. 3). The pinnacle reefs are designated the Zeta Lake Member. The off-reef sequence consists of four members named the Lobstick and Bigoray (lower Nisku) and the Cynthia and Wolf Lake (upper Nisku).