Interaction between CO2-rich acidic water, hydrated Portland cement and sedimentary rocks: Column experiments and reactive transport modeling

Abstract

Percolation experiments, using columns filled with alternating layers of hydrated Portland cement and crushed sedimentary rocks, were conducted at PCO2 = 10 bar and 60 °C. Limestone, sandstone and marl were representative of reservoir and cap rocks for a geologic CO2 storage site. The injected solution was at equilibrium with gypsum and equilibrated with the CO2. The main reactions were the dissolution of the calcite that constitutes the rocks and the hydrotalcite and portlandite of the Portland cement. The resulting porewaters were supersaturated with respect to aragonite and gypsum, leading to their precipitation. 2D reactive transport simulations successfully reproduced the experimental aqueous chemistry changes caused by the major dissolution of calcite, portlandite and hydrotalcite together with the precipitation of aragonite, dolomite (cement carbonation), gypsum and alunite. Porosity increased to different extents in both cement and rock. Cement degradation was noticeable in all the cases, but even more in the sandstone experiment.Thanks are due to Jordi Bellés (IDAEA-CSIC) and Maite Romero and Eva Prats (Scientific and Technical Services of the University of Barcelona) for their help in assisting in the laboratory, ICP-AES and SEM-EDX analyses, respectively. This study was financed by projects CGL2014-54831-C3-1-R and CGL2017-82331-R (Spanish Ministry of Economy and Competitiveness), with contribution from FEDER funds, and by projects CEX2018-000794-S (Spanish Ministry of Science and Innovation) and 2017SGR 1733 (Catalan Government). The manuscript has greatly benefited from the thorough comments of the Associated Editor, Dr. Karen H. Johannenson, and three anonymous reviewers.Peer reviewe