(398e) Sandstone Deformation By CO2 Adsorption

Sahar Bakhshian and Muhammad Sahimi

 

Understanding CO₂ adsorption in underground porous formations provides significant information about their potential for the geological storage of CO₂ in such porous media in order to mitigate the impact of carbon emissions on the climate. The present work aims to study adsorption of CO₂ in sandstone formations over a wide temperature and pressure range through a comprehensive model. We adopt a three-dimensional (3D) image of the Mt. Simon sandstone, the target reservoir for a pilot CO₂sequestration project conducted by the Illinois State Geological Survey, and study sorption and deformation in it.

We have developed a model based on the energetics of the system that couples gas adsorption with the host-guest interaction and structural deformation of the sandstone. The total energy of the system – the rock plus the gas – is written as the sum of three terms: The elastic energy of the material, the fluid-phase energy, and the interaction energy between the fluid (gas) and the solid matrix. By minimizing the total energy with respect to both the fluid’s density and the displacement field of the solid we derive the governing equations for both. The equations are then solved by the finite-element method. Adsorption/desorption isotherms, along with the spatial distribution of the induced strain in the sandstone, are then computed. When the model was applied to sorption of CO₂ in the sandstone samples, all the reported experimental features of the phenomena were reproduced.