Reviewed by E.O. Frind and J.W. Molson
January 11, 2010


We have briefly reviewed this paper consisting of 7 chapters plus a slide show, focusing on the text portion. The main thrust of the paper is that there exists a physical process the author chooses to give the term "buoyancy reversal", and that this process can be used to advantage in the sequestration of CO2 in geologic formations. In addition, the author has identified a number of deficiencies in conventional subsurface modelling techniques.

Our review shows that buoyancy reversal exists, although we might choose a slightly different term to describe this phenomenon. This phenomenon is a natural physical process, and the conditions under which it occurs can be readily predicted. Any groundwater model based on sound fundamental theories should be able to predict buoyancy reversal under the appropriate conditions.

With regard to modelling deficiencies, we are confident that standard techniques used in hydrogeology, at least as far as models originated and developed at the University of Waterloo are concerned, are sound. The development of groundwater models at Waterloo started under the direction of the first reviewer in the 1970s, initially in close cooperation with George Pinder at Princeton University. Our models are based on, and are consistent with, the fundamental theories postulated by Hubbert (1940).

We cannot comment on the validity of reservoir simulation models used in the oil industry. However, on the basis of the evidence presented by the author, we agree that certain reservoir simulation models may have deficiencies which would make them unsuitable for application to groundwater systems, including CO2 sequestration.

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