Assessing CO2 Mineralization and Sequestration Potential in Saudi Basaltic Rocks

To achieve a low-carbon economy, storing carbon dioxide in the Earth's crust by converting it into minerals within basalt rocks is a promising method. This study explores CO₂ interaction with Saudi scoriaceous (SB) and dense (DB) basalts to assess their capacity for CO₂ storage. SB contains augite, olivine, clinopyroxene, and enstatite, while DB is composed of anorthite, augite, olivine, orthopyroxene, and diopside.

SB and DB samples were aged in a supercritical CO₂/brine system at 50°C and 1450 psi for a month. Interfacial tension (IFT) was studied across various pressures at 50°C, and contact angles were measured at room conditions and under the specific conditions of 1450 psi and 50°C. Surface compositional analysis of SB and DB was conducted using scanning electron microscopy (SEM), x-ray fluorescence (XRF), and x-ray diffraction (XRD) before and after CO₂ exposure. Micro-CT scans were performed pre- and post-exposure to assess in situ mineralization. DB, characterized by minimal porosity and permeability, showed potential for CO₂ interaction predominantly on fractured surfaces. However, the DB core sample lacked fractures, so the surface area was the primary place of interaction. In contrast, SB displayed considerable porosity and permeability, indicating a broader area for potential CO₂ interaction.

The results from the IFT measurements revealed a pressure-sensitive pattern, with significant alterations at lower pressures and smaller ones at higher pressures, essential for assessing CO₂ storage potential. Under standard conditions, SB and dense DB exhibited water-wetting properties. However, in a supercritical CO₂/Brine environment, their wettability significantly changed: contact angles increased from 32.9° to 85.8° for DB, and  from 42.6° to 104° for SB, indicating a move towards intermediate water wetness in a CO₂ environment. These results highlight the potential for CO₂ storage in basaltic formations and the complex dynamics of CO₂-brine-rock interactions. Micro CT and SEM analyses showed dissolution, precipitation, and surface variations in the rocks during brine-CO₂ exposure. Specifically, SB demonstrated considerable changes in pore structure and surface, indicating a substantial interaction with CO₂. On the other hand, DB, being non-porous in nature, primarily exhibited surface changes. These post-exposure transformations confirm effective CO₂ interaction with the rocks, further supporting the feasibility of CO₂ sequestration in basalt rocks.

Our in-depth understanding of changes in interfacial tension, wettability, and rock morphology is crucial for safely and efficiently storing CO₂ in basaltic rocks. This knowledge contributes to environmental sustainability and innovative climate change mitigation, marking a significant step towards a greener future in Saudi Arabia.