In October 1977, a significant extension to the 50,000,000 bbl Stettler D-3 and D-2 reef oil field was made 28 years after the initial 1949 discovery and 17 years after the field was considered fully delineated by exploratory and development drilling. The Stettler field is among a number of well-documented Upper Devonian reef fields and was seismically and geologically mapped before and after discovery.

The potential of some Alberta reef field extensions became evident with the new oil economic reality following the Arab oil embargo of 1973. Attention was given to the structurally downdip, southwest closing rim of the Stettler dolomitized D-3 atoll during 1977-79 by the drilling of seven successful oil wells beginning with the Geneva Resources 6-17-38-20 W4 test on a prospect created by the speaker.

From November 1977 to January 1, 1981, 122,869 bbl of crude were produced from the 6-17 well at an average rate of 108 bbl oil/day during that period. At least 1,000,000 additional barrels of primary Stettler oil will be produced as a result of these recent extension wells.

The key to this successful prospect was the lead derived from using computer lists and decline curves of production data. By 1977, over 400,000 bbl of oil and less than 20,000 bbl of salt water had been produced from the 1960 Tenneco CPR 12-17-38-20 W4 well. This location was believed by industry in 1960 to have been close to the D-3 reef oil/water contact with an expectation of high water and low oil productivity.

This example of a significant reef extension is a reminder that abundant, economic oil reserves remain to be discovered in other areas by a more realistic use of geology and production information available in existing computer files.

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