Observation of Cement/Sandstone Interface after Reaction with Supercritical CO₂ Using SEM-EDS,  μ-XRD, and  μ-Raman Spectroscopy

Abstract

We observed cement/sandstone interfaces after reaction with supercritical CO₂ using SEM-EDS, μ-XRD, and μ-Raman spectroscopy in order to evaluate chemical reactions of well-cement in CO₂ storage site. To model actual well in geological formation, we prepared a well composite sample consisting of steel casing, Portland cement, and Berea sandstone. The batch experiment was performed for 56 days under a condition of 10 MPa and 50°C. After the batch experiment, a carbonation zone appeared at the cement/sandstone interface, however, the carbonation depth was limited within a few millimeters and the inner part of the cement was not altered. The Ca concentration in the carbonation zone increased 13% in comparison to that in the unaltered cement zone while the Mg, Si, and S concentrations decreased significantly. The predominant crystalline phases in the carbonation zone were calcite, aragonite, and vaterite. In addition, sparse precipitation of CaCO₃ was observed in the pore spaces of the sandstone along the cement/sandstone interface. [DOI: 10.1380/ejssnt.2016.198]