--> Abstract: In-Situ Stress Magnitudes in the Alberta Basin: Implications for Geological Sequestration of Greenhouse and Acid Gases, by Chris Hawkes, Kristine Haug, and Stefan Bachu; #90039 (2005)

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In-Situ Stress Magnitudes in the Alberta Basin: Implications for Geological Sequestration of Greenhouse and Acid Gases

Chris Hawkes1, Kristine Haug2, and Stefan Bachu3
1 University of Saskatchewan, Saskatoon, SK
2 Alberta Energy and Utilities Board - Alberta Geological Survey, Edmonton, AB
3 Alberta Geological Survey, Edmonton, AB

Carbon dioxide capture and sequestration in geological media is a mitigation strategy that may contribute significantly to reducing anthropogenic CO2 emissions into the atmosphere in the near and medium terms. Many factors must be considered in the selection of candidate sites for CO2 and acid gas injection. From a geomechanical point of view, it is necessary to ensure that the integrity of the low-permeability rocks surrounding the injection unit (i.e., the “bounding seal”) is not compromised as a result of injection pressure. If the gas injection pressure exceeds the magnitude of the minimum in-situ stress, hydraulic fracturing may occur, and the integrity of the bounding seal might be compromised. Geomechanical considerations are also important for gas injection into media with permeabilities that are strongly stress-dependent (e.g., coal). In such cases, the identification of reservoirs with low in-situ stress magnitudes provides valuable guidance in the selection of good storage reservoirs.

The Alberta Geological Survey has compiled a database for the Alberta Basin that includes results from drilling leakoff tests, fracture stimulation treatments, and mini-frac and micro-frac tests. A novel methodology used to interpret minimum in-situ stress magnitudes from these data is presented. Regional-scale variations in the minimum in-situ stress magnitude are demonstrated using the results of this analysis. Further, the effects of various factors, such as lithology and reservoir pressure depletion, on minimum in-situ stress magnitude is demonstrated. Finally, the relationship of in-situ stress magnitudes to bounding seal integrity is reviewed.

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