A 400 m long horizontal well was drilled in both the Brazeau River Nisku Aand D pools at a true vertical depth of 3200 m. Both pools have been undervertical hydrocarbon miscible floods for over ten years. The purpose of thesehorizontal wells was to increase ultimate pool recovery by reducing welldrawdown leading to improved GOR behavior.
The location of the horizontal well in the Alisku A pool was selected basedon the existing 2-D seismic data in an effort to further exploit theundeveloped portion of the reservoir. Two side track horizontal holes weredrilled to search for the porous zone in the bottom of the reservoir, prior todrilling the final horizontal hole approximately two meters above the base ofthe porous zone. In the Nisku D pool, vertical seismic profiling was conductedto locate the porous zone and to aid in the design of the length, depth andazimuth of the horizontal wellbore.
Both wells were open hole completed. The initial oil rates were 300–400m3/d, and the expected incremental reserves are approximately 200000 m3 for the Nisku A pool and 260 000 m3 for the Niskud pool, or four and ten percent of their respective OOIP. Because of therelatively high initial oil rate of the horizontal wells, the high expendituresof $5 million for the Nisku A pool and $3.4 million for the Nisku D pool werepaid out during the first year of production.
The Brazeau River Nisku A and D pools are located approximately 150 kmsouthwest of Edmonton, Alberta. Figure 1 shows the location of the Brazeau River Nisku A and D pools along with other producing Nisku reefs in the area.The first A pool well, 11-3148-12 W5M, was drilled in January 1978. The Nisku Dpool was discovered in June 1978 with the drilling of well 7-3348-12 W5M. The Aand D pools are both sweet oil reservoirs containing light, volatile oil havinga density of approximately 800 kg/m3.