Geological Sequestration of Carbon Dioxide

Hydrogeologic variables tend to uctuate randomly and exhibit a multiscale structure. Understanding and quantifying these phenomena is critical for the analysis of uid ow and mass as well as energy transport in subsurface soil and rock environments (Neuman and Di Federico, 2003; Neuman et al., 2008). Whereas random uctuations arise from the complex nature of soil and rock heterogeneity, multiscale behavior reects the hierarchical structure of geologic media. Traditional methods of geostatistical analysis capture some but not all aspects of these behaviors. Among phenomena that traditional methods of geospatial analysis do not capture are non-Gaussian statistics, for example, powerlaw frequency distributions of length scales and mean apertures of fractures in hard rocks, as discussed in Neuman (2008); systematic growth in apparent spatial correlation scale with sampling domain size, for example, as documented for log permeabilities by Gelhar (1993) and Neuman (1994); and growth in apparent longitudinal dispersivity with mean travel distance or residence time of tracers in porous media and fractured rocks (Neuman, 1990).