Proterozoic Potential Hydrocarbon Source Rocks, Western Canada

L. D. Stasiuk, M. G. Fowler, and G. M. Ross
Natural Resources Canada, Calgary, AB

Proterozoic hydrocarbon source rocks are reported from basins around the world, however this has not been the case in western Canada. Our preliminary evaluation indicates that significant source rocks with originally oil-prone kerogen exist in Proterozoic (~ 1.9 to 0.54 Ga) of western Canada. The oldest potential source rocks encountered to date are ~ 1.7-1.9 Ga black schists from McArthur Lake, northern Saskatchewan. TOC (total organic carbon in wt %) average 2 %, which is significant considering the metamorphic level is upper amphibolite to granulite facies. These schists are regional and have been interpreted as ‘widespread anoxic black shales'. Mesoproterozoic black shales of the Douglas Formation (~ 1.5-1.4 Ga) preserved to the west in the Athabasca Basin of northern Saskatchewan contain up to 3 % TOC and average 1 to 1.5 % TOC over 60 m in the condensate-dry gas zone of maturity. The Tetsa and Aida formations of the Muskwa Assemblage (1.6-1.8 Ga) in the Muskwa Range of northeastern British Columbia have TOC of up to 2.2 % at maturity levels of ~ 2.4 to < 3.5 %Ro vitrinite. Calcareous black shales and carbonate source rocks also contain an anisotropic pyrobitumen, indicative of liquid petroleum cracked to gas. Windermere Group strata, ~ 0.80-0.54 Ga, from the Cordillera of Alberta contain 2 noteworthy black shale intervals with above average TOC: slope deposits 15 m thick with 2-4 % TOC and basinal deposits up to 100 m thick having TOC of 0.2 to 0.5 %.

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