Multi-scale Experimentation and Numerical Modeling for Process Understanding of CO2 Attenuation in the shallow subsurface

Abstract

Abstract The goal of this study is to quantify the effects of geologic heterogeneity on the dynamic process of CO 2 attenuation in shallow aquifers through the use of multi-scale laboratory experimentation and numerical modelling. First, an experiment was conducted in an intermediate scale two-dimensional cell that was packed with water-saturated porous media in a simple heterogeneous configuration. Constant-head boundary conditions were applied to the system, and then CO 2 -saturated water was injected through it. As the CO 2 -saturated water migrated through the system, gas phase CO 2 evolved within the porous media, as observed by dielectric saturation sensors. The outflow of CO 2 gas from the top of the system was monitored by a gas flow meter, and the outflow of water from the side of the tank was monitored via collection into a container that was placed on a computer-interfaced scale. After the multiphase CO 2 evolution appeared to have reached steady state, clean water was injected through the cell until all of the CO 2 was expelled from the system. In addition to the experiments, numerical models were performed using the Finite Element Heat and Mass transfer (FEHM) code as a first step toward planning larger scale experiments. Results indicate that the presence of geologic heterogeneity, which is ubiquitous in natural environments, can significantly hinder the migration of CO 2 in the shallow subsurface.