Soil gas as a monitoring tool of deep geological sequestration of carbon dioxide: Results from the three year Monitoring of the Encana Eor Project, Weyburn, Saskatchewan (Canada)

As part of the IEA Weybum CO2 Monitoring and Storage Project, preliminary baseline soil gas data was collected in the summer and autumn of 2001 above the injection area of the EnCana Enhanced Oil Recovery project at the Weybum oilfield in south Saskatchewan. The 2001 data was presented at GHGT-6 in Kyoto. In the autumns of 2002 and 2003, further in situ monitoring of CO2, CO2 flux, O2, CH4, radon (222Rn), and thoron (220Rn) was carried out. Soil gas samples were also collected for the laboratory analysis of helium, permanent gases, sulfur species, and light hydrocarbons. All sampling was repeated over the same 360 point sampling grid and more detailed profiles for both follow-up years. Marked changes in CO2 levels (especially flux) for each of the three-year datasets indicated changes in surface conditions. The radon and thoron data was found to be similar for the three years, but appeared to vary in response to drift composition and seasonal effects, rather than migration from a deep source. © 2005 Elsevier Ltd. All rights reserved.