Geologic storage of CO(2) requires that the caprock sealing the storage rock is highly impermeable to CO(2). Swelling clays, which are important components of caprocks, may interact with CO(2) leading to volume change and potentially impacting the seal quality. The interactions of supercritical (sc) CO(2) with Na saturated montmorillonite clay containing a subsingle layer of water in the interlayer region have been studied by sorption and neutron diffraction techniques. The excess sorption isotherms show maxima at bulk CO(2) densities of ≈ 0.15 g/cm(3), followed by an approximately linear decrease of excess sorption to zero and negative values with increasing CO(2) bulk density. Neutron diffraction experiments on the same clay sample measured interlayer spacing and composition. The results show that limited amounts of CO(2) are sorbed into the interlayer region, leading to depression of the interlayer peak intensity and an increase of the d(001) spacing by ca. 0.5 Å. The density of CO(2) in the clay pores is relatively stable over a wide range of CO(2) pressures at a given temperature, indicating the formation of a clay-CO(2) phase. At the excess sorption maximum, increasing CO(2) sorption with decreasing temperature is observed while the high-pressure sorption properties exhibit weak temperature dependence.
Excess sorption isotherms of supercritical carbon dioxide in mesoporous CPG-10 silica glasses with nominal pore sizes of 7.5 and 35 nm were measured gravimetrically at 35 and 50 °C and pressures of 0À200 bar. Formation of broad maxima in the excess sorption was observed at fluid densities below the bulk critical density. Positive values of excess sorption were measured at bulk densities below 0.7 g/ cm 3 , i.e., the interfacial fluid is denser than the bulk fluid at low pressures. Zero and negative values were obtained at higher densities, i.e., the adsorbed fluid becomes equal to and eventually less dense than the corresponding bulk fluid. Pronounced confinement effects on sorption behavior have been found and further analyzed by normalizing the excess sorption to the adsorbent surface area and pore volume, yielding new insight into supercritical fluid adsorption in this range of pore sizes and P, T conditions. If normalized to the specific surface area, the excess sorption is higher for the 35 nm pore size material, but the pore volume normalized excess sorption is higher for the 7.5 nm pore size material. With increasing pore width, the excess sorption peak position shifts to higher pressure. Both CPG-10 materials exhibit regions of constant mean pore fluid density as a function of bulk CO 2 density at 35 °C but not at 50 °C. This region is located between the excess sorption peak maximum and the adsorption/depletion transition point. Applied to the situation of CO 2 sequestration in dry sandstone formations, the results of this study indicate that carbon storage capacity is enhanced by sorption effects, particularly at low temperature and in narrow pores with high surface to volume ratios.
a b s t r a c tCarbon capture, utilization and storage (CCUS) in saline reservoirs in sedimentary formations has the potential to reduce the impact of fossil fuel combustion on climate change by reducing CO 2 emissions to the atmosphere and storing the CO 2 in geologic formations in perpetuity. At pressure and temperature (PT) conditions relevant to CCUS, CO 2 is less dense than the pre-existing brine in the formation, and the more buoyant CO 2 will migrate to the top of the formation where it will be in contact with cap rock. Interactions between clay-rich shale cap rocks and CO 2 are poorly understood at PT conditions appropriate for CCUS in saline formations. In this study, the interaction of CO 2 with clay minerals in the cap rock overlying a saline formation has been examined using Na + exchanged montmorillonite (Mt) (Na + -STx-1) (Na + Mt) as an analog for clay-rich shale. Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR) was used to discern mechanistic information for CO 2 interaction with hydrated (both one-and two-water layers) and relatively dehydrated (both dehydrated layers and one-water layers) Na + -STx-1 at 35°C and 50°C and CO 2 pressure from 0-5.9 MPa. CO 2 -induced perturbations associated with the water layer and Na + -STx-1 vibrational modes such as AlAlOH and AlMgOH were examined. Data indicate that CO 2 is preferentially incorporated into the interlayer space, with relatively dehydrated Na + -STx-1 capable of incorporating more CO 2 compared to hydrated Na + -STx-1. Spectroscopic data provide no evidence of formation of carbonate minerals or the interaction of CO 2 with sodium cations in the Na + -STx-1 structure.Published by Elsevier B.V.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.