Influence of Small Scale Heterogeneity on COsub2/sub Trapping Processes in Deep Saline Aquifers

<p> <p id="x-x-spar0005"> The physical mechanism of CO ₂ trapping in porous media by capillary trapping (pore scale) incorporates a number of related processes, i.e. residual trapping, trapping due to hysteresis of the relative permeability, and trapping due to hysteresis of the capillary pressure. Additionally CO ₂ may be trapped in heterogeneous media due to difference in capillary pressure entry points for different materials (facies scale). The amount of CO ₂ trapped by these processes depends upon a complex system of non-linear and hysteretic relationships including how relative permeability and capillary pressure vary with brine and CO ₂ saturation, and upon the spatial variation in these relationships as caused by geologic heterogeneity. <p id="x-x-spar0010"> Geological heterogeneities affect the dynamics of CO ₂ plumes in subsurface environments. Recent studies have led to new conceptual and quantitative models for sedimentary architecture in fluvial deposits over a range of scales that are relevant to the performance of some deep saline reservoirs. We investigated how the dynamics of a CO ₂ plume, during and after injection, is influenced by the hierarchical and multi-scale stratal architecture in such reservoirs. The results strongly suggest that representing small scales features (decimeter to meter), including their organization within a hierarchy of larger-scale features, is critical to understanding trapping processes. </p> </p></p>