Numerical simulations of CO2 sequestration in basaltic rock formations: Challenges for optimizing mineral-fluid reactions

Abstract

Numerical simulations were carried out for determining the chemical reactions relevant for the sequestration of CO2 in basaltic rock formations. The mineralogy of natural geological systems consists of silicate minerals such as the phyllosilicates and zeolites that form complex solid solutions. Using the GEMS code package based on Gibbs energy minimization, combined with the new MINES database, we can now simulate the solubility of these multicomponent and multisite mineral solid solutions in basaltic rocks. This study explores the varying effects of CO2 partial pressures, basaltic glass dissolution kinetics and reaction time on the complex chemistry of the overall CO2-water-basalt reaction path. The simulations indicate four reaction progress stages with the competing reactions between smectites (di- and trioctahedral) and Ca-Fe-Mg-carbonates controlling the amount of CO2 mineralized. A better understanding of these key mineral-fluid reactions and improvement of their thermodynamic models is critical for making more acurate predictive calculations. This comprises the basis for extending the simulations to reactive transport models, and for the assessment of the feasibility of long-term CO2 storage in basaltic rock formations.