The Study of Natural Fractures in a Reef Complex, Norman Wells Oil Field, Canada
Published:January 01, 1988
J. P. R. Irish, R. H. Kempthorne, 1988. "The Study of Natural Fractures in a Reef Complex, Norman Wells Oil Field, Canada", Reservoir Sedimentology, Roderick W. Tillman, K. J. Weber
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Hydrocarbons at Norman Wells, Northwest Territories, Canada, are pooled in the Devonian Kee Scarp Formation limestone reef buildup which is 15 mi (25 km) long and 5 mi (8 km) wide. The reef complex began to develop during Upper Middle Devonian time on shale banks of the Hare Indian Formation. Minor variations in sea level localized major reef growth on a thin, open marine platform along basinward edges of the Hare Indian shales. Reef growth proceeded during two major shoaling-upward cycles and was terminated by the advancing clastic sediments of the Canol and Imperial Formations, which serve as the top seal for the reefal buildups. The Kee Scarp reef at Norman Wells attains a maximum thickness of 535 ft (160 m) with a reservoir thickness of 360 ft (110 m). The formation has been divided into four zones, named in ascending order: Kl, K2, K3, and K4. The Kl zone is interpreted as platform, and the K2-K4 zones as reefal buildup.
In 1920, Imperial Oil Limited drilled the discovery well for the Norman Wells field near oil seepages at Norman Wells 900 miles (1,500 km) north of Edmonton, Alberta. Oil is stratigraphically trapped in the extreme updip end of the reef buildup. There is no gas cap, and a limited water leg provides no fluid pressure support to assist in producing the oil.
The major development plan for producing a portion of the remaining oil at Norman Wells field is discussed in this paper. The plan is based on a recent synergistic geological and engineering study of the reservoir. Information from six oriented cores, well tests, fluid and pressure surveys, outcrop studies, and surface photos has shown that natural vertical fractures present in the reservoir have a strong N30° E orientation. The proposed development plan will make use of the geological and engineering model as well as the directional permeabilities resulting from natural fractures.
Figures & Tables
This volume is a collection of papers which focus on the sedimentology of siliciclastic sandstone and carbonate reservoirs. The papers were selected to show how detailed sedimentologic descriptions, when combined with engineering or other subsurface geologic techniques, yield reservoir models which may be used for reservoir management during field development and during secondary or tertiary enhanced oil recovery. In all the papers the framework for the field descriptions relies heavily of full-diameter cores. In addition to conventional 4-inch-diameter cores, frozen and rubber-sleeve cores were utilized in one or more of the studies. In addition to cores, at least one other geologic or engineering technique is integrated into each study. This integration of sedimentologic descriptions with other techniques gives rise to synergism.