The effects of long-term supercritical CO2 exposure on Zululand Basin core samples

• Published in: Energy (Oxford) 2021-04, Vol.220, p.119806, Article 119806
• Main Authors: Mavhengere, P., Wagner, N., Malumbazo, N.
• Format: Article
• Language: English
• Subjects: Adsorption; Calcite; Carbon dioxide; Carbon dioxide emissions; Carbon dioxide fixation; Carbon sequestration; CO2 storage; Composition; Dissolution; Fourier transforms; Geology; Infrared spectroscopy; Low pressure; Mineral alterations; Plagioclase; Supercritical pressure; Surface chemistry; X-ray diffraction; Zululand basin
• ISSN: 0360-5442; 1873-6785
• DOI: 10.1016/j.energy.2021.119806

Carbon dioxide (CO2) sequestration in geological formations is a viable solution for ensuring coal-based energy supply whilst reducing CO2 emissions. The variation in the microstructure and composition of geological formations before and after CO2 storage plays a significant role in CO2 sequestration. Three core samples obtained from the Zululand Basin in South Africa were exposed to supercritical CO2 (ScCO2) in the presence of water under typical hydrothermal conditions (175 bar, 70 °C) for up to 2 months. The samples were characterized pre- and post-treatment using X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), low pressure nitrogen (N2) adsorption and low pressure CO2 adsorption. Physical and chemical structural changes were observed in all three samples after treatment, to varying degrees. Mineral alterations were observed in the three samples, including plagioclase and calcite dissolution/precipitation and quartz composition changes. Dissolution of organic components and surface chemistry alterations were found in two of the core samples. Increases in pore volume, surface area and CO2 adsorption capacity were observed in all studied samples after CO2 treatment. •Mineral alterations to varying degrees, were observed after ScCO2-water treatment.•Alterations in the surface chemistry of the sandstone core samples was observed in two of the three core samples.•ScCO2-water treatment of core samples resulted in increases in micropore and mesopore surface areas.•Limited influence on the macropores was observed in all three sandstone core samples.•The pore size distribution was altered in all three samples after treatment.