Field Trip Details
For more information, contact Kristin Briard at: firstname.lastname@example.org.
The Devonian of western Canada is famous for its thick (100’s of metres in many cases) succession of carbonates that accumulated as carbonate platform and reef deposits at a time when Alberta was flooded by a vast inland sea and located in an equatorial position. Many of these platform and reef deposits have hosted significant conventional oil and gas accumulations, and the Grosmont—Upper Ireton—Nisku succession, estimated to host >500 billion barrels of bitumen, is the largest unconventional carbonate oil field in the world. Vuggy fractured dolostones are a primary reservoir facies in this succession, but this type of facies can be difficult to fully assess in core, and accessible surface exposures of the Grosmont with this facies do not exist.
Upper Devonian fossiliferous vuggy dolostones assigned to the Cairn and Southesk Formations, deposited at a roughly similar time to the Grosmont Formation, can be easily viewed along trails at Grassi Lakes, Canmore. These deposits accumulated on an open marine carbonate ramp as bedded deposits and locally formed small mounds. An ancient type of calcareous sponge called a “stromatoporoid” is abundant in these mounds and bedded deposits, but in many cases was dissolved out to form the large vugs. The Grassi Lakes section, in its upper parts, includes bedded lagoon and peritidal deposits that include a number of classic Devonian facies including Amphipora-rich deposits. Similar facies are found in the Grosmont Formation.
The field excursion will visit the Cairn-Southesk succession at Grassi Lakes near Canmore, Alberta where the participants can view—at reservoir scale—bedded and mounded vuggy dolostones as well as bedded lagoon deposits rich in Amphipora. The excursion will allow for discussion of the geological nature of these reservoir facies, challenges in their characterization at the well-bore and seismic scale, and the role of fractures in enhancing permeability. Ultimately the excursion will be an excellent opportunity to discuss how such facies may perform as thermal reservoirs.
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