Abstract

A system of CO2 and brine flowing through permeable rock, relevant to CO2 storage underground, includes a wide range of physical and chemical processes. These are conventionally modeled using continuum rock properties ­ permeability, dispersion, mineral surface area. The foundational assumption that within the rocks there exists a scale where the properties are homogenous is a significant source of uncertainty and inaccuracy. Improving on this, however, presents challenges for both modeling and observation. How can we derive information from laboratory observations that is both practical to obtain and practical to use for more rigorous modeling efforts?

I will present the results of investigations into many of the physico-chemical processes relevant to CO2 storage across the scales that can be observed in the laboratory [1-3]. Within the pores of the rocks synchrotron and laboratory X-ray micro tomography has been used to observe dynamic and equilibrium fluid displacement. It has also been used to characterize the distribution of reactive mineral surface area. At the centimeter scale conventional X-ray imaging has been used to characterize solute transport in 3D and to evaluate the impact of rock heterogeneity on multiphase flow and trapping. Combined the results show the pervasive role of heterogeneity on macroscopic flow and reactive processes. They also provide insight into viable paths for incorporating this information into more rigorous models of multiphase flow and reactive transport in the subsurface.