Dispersion and mixing in porous media (Carbon Capture and Storage)
Carbon Capture and Storage is a promising solution to curb greenhouse gas emissions to the atmosphere in our fight against climate change.
It is now widely accepted that the global warming of the atmosphere observed in the last 150 years is due to an increase in the atmospheric concentrations of greenhouse gases, and that the storage of carbon dioxide (CO2) in deep geological formations is a feasible medium term solution.
In this experimental project, we investigate dispersion and mixing of CO2 through porous media. The aim of the project is to validate previous computational studies that suggest that partial dissolution of supercritical CO2 into a brine results in a mixture that is denser than the brine underneath, which triggers a gravitational instability that causes the mixture to be advected downwards through the brine. If this is indeed the case, this instability could be harnnes to store carbon dioxide at the bottom of the aquifer, where it can remain sequestrated for a very long time.
In order to permit a quatitative and analytic interpretation of the observed porous dispersion in gravitational fingering instability, we use ‘porous’ Hele shaw cells that are manufactured by means of classical methods used for microfluidics devices. Unlike the non porous Hele-Shaw cells, the porous Hele-Shaw cells are patterned to mimic an actual granular medium (hexagonal, square or random patterns with controlled distribution and correlation length). CO2 enriched zones are visualized by means of a pH sensitive indicator, which enables to extract quantitative concentration fields and measure the dispersion characteristics.
This project will provide experimental results that will be used to validate current state-of-the-art computational models regarding dispersion and mixing in porous media, shining new light on dispersion processes governing CO2 transport in non-homogeneous aquifers and the feasibility of harnessing porosity and gravitaitonal instabilities to store CO2 in deep geological formations.
Dr Francois Nadal - Senior Lecturer in Fluid Engineering
"It is exciting to work with colleagues at the British Geological Survey (BGS, UK) and Aix-Marseille University (France) on this project. Computational studies to date use continuum/Darcy scale models, which neglect all the physics occurring at the pore scale. Therefore, being able to provide experimental data to validate computational predictions and estimate more accurately the typical CO2 dissolution time in non-homogeneous aquifers is very important."