Assessing CO2 mineralization and sequestration potential in Saudi Arabian basaltic rocks

This study evaluates the potential of sequestering carbon dioxide within the Earth’s crust by examining the interactions of CO 2 with two types of basalts: scoriaceous (SB) and dense (DB), which is non-scoriaceous lava. The goal is to determine their respective capacities for carbon dioxide storage. SB is composed of augite, olivine, clinopyroxene, and enstatite, whereas DB comprises anorthite, augite, olivine, orthopyroxene, and diopside. Both SB and DB samples underwent aging in a supercritical CO 2 /brine environment at 50 °C and 1450 psi for one month. The study encompasses interfacial tension (IFT) measurements at various pressures, temperatures, and contact angles under ambient and experimental conditions. Compositional changes were analyzed using X-ray diffraction (XRD) pre- and post-CO 2 exposure, and micro-CT scans were employed to evaluate in-situ mineralization. Additionally, petrophysical and mechanical properties were assessed for both rock types, alongside ion concentrations, via ion chromatography. The findings indicate that DB, characterized by low porosity and permeability, primarily interacts with CO 2 at fractured surfaces; however, due to a lack of fractures in the tested DB core sample, the surface area served as the main interaction site. In contrast, the more porous and permeable SB facilitated broader CO 2 interactions. Interfacial tension (IFT) measurements exhibited a variation with pressure, which is crucial for assessing the effectiveness of CO 2 storage. The wettability significantly shifted in a supercritical CO 2 /brine context, with contact angles for DB and SB increasing markedly, suggesting a transition towards intermediate water wetness. Micro-CT analysis reveals dissolution, precipitation, and morphological alteration in the rocks following exposure to the brine-CO 2 environment. Notably, SB exhibits significant pore structure and surface changes, indicating extensive CO 2 interaction, whereas DB showed primarily surface modifications. Alterations in the petrophysical and mechanical properties, including permeability, Poisson’s ratio, and Young’s modulus, were observed for both rock types following CO 2 exposure. This comprehensive analysis underscores the importance of understanding changes in interfacial tension, wettability, and rock morphology for effective and safe CO 2 storage in basaltic formations. These insights are vital for advancing environmental sustainability and providing innovative solutions to climate change mitigation, thereby contributing significantly towards achieving a low-carbon global future.