--> Abstract: Lower Cretaceous Petroleum Systems in Southern Alberta, Canada, by Kim Manzano-Kareah, Cynthia L. Riediger, and Martin Fowler; #90039 (2005)

Datapages, Inc.Print this page

Lower Cretaceous Petroleum Systems in Southern Alberta, Canada

Kim Manzano-Kareah1, Cynthia L. Riediger2, and Martin Fowler3
1 Institute of Geological and Nuclear Sciences, Lower Hutt, New Zealand
2 University of Calgary, Calgary, AB
3 Geological Survey of Canada, Calgary, AB

Lower Cretaceous reservoirs in the Western Canada Sedimentary Basin are estimated to contain 2668 x106m3 initial volume of oil in place, approximately 37% of the total initial volume of conventional oil in place in the basin. Over 50 % of these Lower Cretaceous conventional oils, however, are heavy oils (API gravity < 25°).

In southern Alberta (Township 1 – 40, Range 1W4 – 7W5), oils in Lower Cretaceous Mannville and Jurassic Ellis reservoirs show a wide variation in quality (sulfur content: 0.5 – 4.0 wt.%; API gravity: 13 – 43°). Geochemical analyses of over 280 oils from the Lower Cretaceous Mannville and Jurassic Ellis reservoirs have demonstrated that the variation in oil quality is primarily due to differences in oils generated from different source rocks and biodegradation of oils in reservoirs.

Oils produced from the Lower Cretaceous Mannville and Jurassic Ellis groups in southern Alberta were generated from five different source rocks: the Devonian Duvernay Formation, the Devonian-Mississippian Exshaw Formation, a probable Paleozoic source, a probable Jurassic source (Rierdon/Fernie shales), and the Cretaceous Ostracod Zone. Mixing of oils from different source rocks is common in the northern portion of the study area. Biodegradation and the mixing of degraded with non-degraded oils are the main factors controlling the variation in oil quality within a given family. The much improved understanding of oil families and degree of biodegradation integrated with knowledge of reservoir trends, subcrop edges, structure and hydrodynamics allows for more accurate mapping of likely oil and gas migration pathways.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005