About This Item

Share This Item

The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 65 (1981)

Issue: 5. (May)

First Page: 925

Last Page: 925

Title: Athabasca Oil Sands--Facies Characteristics and Distribution: ABSTRACT

Author(s): Peter D. Flach

Article Type: Meeting abstract


The Athabasca oil sands represent one of the world's great untapped energy resources, with in-place bitumen reserves estimated at 146 × 109 m3 (922 × 109 bbl). About 10% of the reserves lie close enough to the surface to be mined in open-pit operations, but the vast majority (~ 90%) must be developed by as yet unproved in-situ means. A geologic understanding of the facies is crucial in applying in-situ techniques.

Most of the rich oil sand bodies are channel deposits in the Middle Member of the Lower Cretaceous McMurray Formation. This member, averaging 35 m in thickness, is dominated by upward-fining sequences interpreted as meandering river deposits. Earlier detailed work on epsilon cross-strata in outcrop confirms the interpretation of single channels 20 to 30 m deep. The channel sequence is dominated by trough cross-bedded sands at the base, grading upward into thinner bedded rippled sand units with increasingly abundant clay drapes toward the top. Burrowing is common in the upper parts but palynology indicates a basically freshwater setting. The channels are part of a complex fluvial-deltaic system associated with standing bodies of fresh to brackish water.

The fluvial Lower Member fills lows in the underlying Devonian limestone. The sands are commonly very argillaceous or water-bearing, but in places, form good reservoirs.

The Upper Member is a 20-m-thick sequence of shoreline deposits. This member is generally very argillaceous, but extensive upward-coarsening marine sands near the top commonly make good reservoirs.

End_of_Article - Last_Page 925------------

Copyright 1997 American Association of Petroleum Geologists