Exploration in Mississippian Carbonate Facies, Central Alberta, Canada: Old and New Approaches

Hamid A. Majid

Hydrocarbon reservoirs of the Blueridge, Greencourt, and Windfall fields in central Alberta occur as carbonate subcrop traps of Banff, Pekisko, and Shunda formations of the Mississippian age. Core and sample examination reveals eleven distinct lithofacies. The Banff lithofacies include lower siliciclastic, oolitic grainstone, argillaceous mudstone, brachiopod-bryozoan wackestone, and upper siliciclastic. The lithofacies of the Pekisko are peloidal-bryozoan wackestone and dolomite. Shunda lithofacies are comprised of basal argillaceous mudstone, dolomite-shale, peloidal packstone, and cherty wackestone. The lithofacies of each of these three formations represent transgressive-regressive cycles deposited on a low-relief carbonate platform. The Shunda Formation has a good potential for oil and gas subcrop prospects, particularly south of Township 64, where porous and permeable dolomite and limestone occur.

However, there is a possibility of finding a different play type in the Mississippian of central Alberta where the potential exists for high-energy carbonate skeletal sand shoal reservoirs. It is possible that downdip traps unrelated to the Mississippian subcrop can be found. Such traps would be fundamentally related to the structural and depositional history of the area. Carbonate shoals may possibly be in areas of differential drape over the ancient faulted structural framework of the basement. Rational exploration for such predominantly stratigraphic-type traps in the Mississippian units requires a detailed understanding of the lithology, geometry, and diagenetic (compaction) parameters of skeletal shoal reservoirs and adjacent facies. Traditional seismic methods are not capable of detecting such thin reservoirs within the enclosing sedimentary rocks.

AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.