Locking up carbon dioxide in saline aquifers
One of the most pressing problems facing humanity is how to slow down global warming and climate change. The emission of CO2 gas to the atmosphere is one of the main causes of warming, so a possible defence is locking it up. Aquifers carrying saline water could be a suitable place for CO2 sequestration.The 'CO2 Multiphase reactive transport modelling' (CO2-MATE) project used both high-resolution modelling and experimental methods to study CO2 flow and transport in saline-water aquifers. The aim was reach a better understanding of trapping mechanisms in order to model them realistically.The researchers used a Darcy-Boussinesq model in which the Rayleigh number is the important parameter. By means of a newly developed theoretical relationship, they showed that the scalar dissipation rate determines the dissolution flux and the rate of fluid mixing. Computational evidence indicated that under certain conditions the dissolution flux was constant and independent of the Rayleigh number. Their findings suggest that there is a need for alternative explanations for non-linear scaling. Project work also showed that the flux dynamics and some macroscopic features of the migrating current could be reproduced using a one-dimensional sharp-interface model. Other aspects studied included aquifer heterogeneity, and the dissolution of calcite during convective mixing of CO2 in a carbonate aquifer.The results of the work done on CO2-MATE will help in the development of practicable numerical tools. In turn, this could improve the planning and monitoring of sites where CO2 is injected.
Keywords
Carbon dioxide sequestration, aquifers, CO2 flow, flux dynamics, numerical modelling.
