부산대학교 도서관

Abstract: Crushed rock from two caprock samples, a carbonate-rich shale and a clay-rich shale, were reacted with a mixture of brine and supercritical CO2 (CO2–brine) in a laboratory batch reactor, at different temperature and pressure conditions. The samples were cored from a proposed underground CO2 storage site near the town of Longyearbyen in Svalbard. The reacting fluid was a mixture of 1M NaCl solution and CO2 (110bar) and the water/rock ratio was 20:1. Carbon dioxide was injected into the reactors after the solution had been bubbled with N2, in order to mimic O2-depleted natural storage conditions. A control reaction was also run on the clay-rich shale sample, where the crushed rock was reacted with brine (CO2-free brine) at the same experimental conditions. A total of 8 batch reaction experiments were run at temperatures ranging from 80 to 250°C and total pressures of 110bar (∼40bar for the control experiment). The experiments lasted 1–5weeks. Fluid analysis showed that the aqueous concentration of major elements (i.e. Ca, Mg, Fe, K, Al) and SiO2 increased in all experiments. Release rates of Fe and SiO2 were more pronounced in solutions reacted with CO2–brine as compared to those reacted with CO2-free brine. For samples reacted with the CO2–brine, lower temperature reactions (80°C) released much more Fe and SiO2 than higher temperature reactions (150–250°C). Analysis by SEM and XRD of reacted solids also revealed changes in mineralogical compositions. The carbonate-rich shale was more reactive at 250°C, as revealed by the dissolution of plagioclase and clay minerals (illite and chlorite), dissolution and re-precipitation of carbonates, and the formation of smectite. Carbon dioxide was also permanently sequestered as calcite in the same sample. The clay-rich shale reacted with CO2–brine did not show major mineralogical alteration. However, a significant amount of analcime was formed in the clay-rich shale reacted with CO2-free brine; while no trace of analcime was observed in either of the samples reacted with CO2–brine. [Copyright &y& Elsevier]