ABSTRACT

Biohermal reefs, herein designated the Rainbow Member of the Keg River Formation, (Middle Devonian) are present in the Rainbow Field area of northwestern Alberta. The Rainbow Member is 756 feet thick at the Banff Aquitaine Rainbow West 7-32 discovery well, whereas the off-reef equivalent, the Upper Keg River Member, is only 153 feet thick at the Imperial Black Creek 10-27 well, four miles west of the discovery.

A formational nomenclature is presented for the Rainbow area which includes the following new stratigraphic names: Lower Keg River Member, Upper Keg River Member and Rainbow Member, all of which are part of the Keg River Formation, and Black Creek Member which is the lower member of the Muskeg Formation.

The discovery of a thick oil and gas pay zone in the Rainbow Member at the Banff Aquitaine Rainbow West 7-32 well has opened a new and important phase in exploration for oil and gas in western Canada.