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Buschkuehle, Beate E.1, Matthias Grobe1
(1) Alberta Energy and Utilities Board - Alberta Geological Survey, Edmonton, AB

ABSTRACT: Geology of the Upper Devonian Grosmont Carbonate Bitumen Deposit, Northern Alberta, Canada

The Devonian Grosmont Formation underlies the Cretaceous Athabasca Oil Sands deposit in Alberta. It contains an estimated 50 billion m3 of heavy crude bitumen, representing about one sixth of the total hydrocarbon accumulation in the area. Pilot operations for in-situ thermal recovery in the past yielded mixed results and were terminated due to unfavorable economic conditions. However, recent advances in recovery techniques are likely to rejuvenate the industry’s interest in exploiting the Grosmont bitumen deposit.
Regional maps and cross-sections demonstrate the stratigraphic context and the internal platform architecture of the Grosmont. An extensive core study from reservoir and non-reservoir facies introduces the geological factors controlling bitumen distribution.
The Grosmont Formation is subdivided by three shale beds into four units, the Lower Grosmont (LG), the Upper Grosmont 1 (UG1), the Upper Grosmont 2 (UG2) and the Upper Grosmont 3 (UG3). The UG1 and UG2 are the main reservoir units with porosities ranging from 7 to 20% and bitumen saturation between 70% and 100%. The reservoir quality in the carbonates is controlled by a combination of depositional facies and diagenesis, specifically dolomitization and karstification. Karst processes generally increased porosity and permeability but were also detrimental to seal effectiveness. The heterogeneity of the reservoir, the low effective permeabilities due to high bitumen saturation, and the high viscosity of the heavily biodegraded bitumen are the main hurdles in applying in-situ recovery schemes. An interdisciplinary approach combining geological knowledge with reservoir and process engineering expertise is required to provide the tools to overcome these challenges.

 

AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.