| The Upper Devonian Grosmont reservoir in Alberta, Canada, is the single largest carbonate bitumen reservoir in the world, with an estimated 400 billion barrels of bitumen in place. The Grosmont bitumen formed from light crude oil via extensive biodegradation, which produced extremely high in-situ viscosities of >1 million cP. Forty nine samples from fifteen wells were selected for rheological behavior, viscosity, and biodegradation pattern analysis. In addition, various methods of viscosity determination were compared.Results indicate that the Grosmont bitumen is essentially a non-Newtonian fluid at in-situ conditions, exhibiting a distinctive shear-thinning behavior at T < 40°C. Neglecting this character will cause inaccurate viscosity measurements. The viscosity variations in the Grosmont reservoir are cyclic with depth and are stratigraphically controlled. The bitumen exhibits 3 levels of biodegradation. Biodegradation parameters from hopanes and tricyclic terpanes may potentially be used for bitumen quality prediction. |
