Acid-gas injection at West Stoddart, British Columbia: An analogue for the detailed hydrogeological characterization of a CO2 sequestration site

Geological sequestration of CO2 is an option for significantly reducing emissions into the atmosphere. Various hydrocarbon companies in western Canada are currently injecting acid-gas (CO2 and H2S) into deep subsurface formations. At West Stoddart, in northeast British Columbia, acid-gas has been injected since 1998 at 1600 m depth into sandstones of the Triassic Halfway Formation, which forms a regional aquifer. A comprehensive subsurface characterization was conducted of the regional and local-scale geology, reservoir characteristics, mineralogy, in situ fluid properties, and hydrogeology. Preliminary results from geochemical and numerical multi-phase flow modelling suggest that the majority of the injected acid-gas will dissolve in the formation water and remain within a radius of a few kilometres of the injection well. The experience with the acid-gas injection at West Stoddart and other operations in the Alberta Basin has shown that the process of large-scale CO2-injection into deep aquifers is technically feasible.