Selection of Monitoring Sites at Acid-Gas Injection Operations in Western Canada

Stefan Bachu
Alberta Geological Survey, Edmonton, AB

Carbon dioxide capture and geological storage has been identified as an important means for reducing anthropogenic CO₂ emissions into the atmosphere. To date there is limited knowledge and experience regarding the fate of the injected CO₂. Acid gas, a mixture of CO₂ and H₂S, is being injected in western Canada at more than 40 locations into depleted oil and gas reservoirs, and deep saline aquifers. These acid-gas injection operations constitute a commercial-scale analogue for CO₂ geological storage and provide an opportunity to understand better the fate of injected gases into the subsurface. Implementation of a monitoring program at one or more of these operations would contribute to understanding the fate of the injected gases, hence to the developing of a sound monitoring and regulatory environment for the large-scale implementation of CO₂ capture and geological storage.

A methodology for the screening and selection of top candidate sites for the implementation of a monitoring program at acid or greenhouse gas injection sites has been developed and will be presented. The method takes into account surface and subsurface characteristics of the operation; properties of the injected gas, reservoir oil or gas, and formation water; rock type and properties; status of wells in the vicinity of the injection site; and the potential for intrusive and non-intrusive monitoring. Application of this algorithm for site screening and ranking ensures repeatability and objectivity. The method allows flexibility and sensitivity analysis by permitting changes in weighting factors and coefficients such that various scenarios can be run and compared.

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