Enhancing the CO 2 trapping capacity of Saudi Arabian basalt via nanofluid treatment: Implications for CO 2 geo-storage.

Mineralization reactions in basaltic formations have gained recent interest as an effective method for CO ₂ geo-storage in order to mitigate anthropogenic greenhouse gas emissions. The CO ₂ /rock interactions, including interfacial tension and wettability, are crucial factors in determining the CO ₂ trapping capacity and the feasibility of CO ₂ geological storage in these formations. The Red Sea geological coast in Saudi Arabia has many basaltic formations, and their wetting characteristics are rarely reported in the literature. Moreover, organic acid contamination is inherent in geo-storage formations and significantly impacts their CO ₂ geo-storage capacities. Hence, to reverse the organic effect, the influence of various SiO ₂ nanofluid concentrations (0.05-0.75 wt%) on the CO ₂ -wettability of organic-acid aged Saudi Arabian (SA) basalt is evaluated herein at 323 K and various pressures (0.1-20 MPa) via contact angle measurements. The SA basalt substrates are characterized via various techniques, including atomic force microscopy, energy dispersive spectroscopy, scanning electron microscopy, and others. In addition, the CO ₂ column heights that correspond to the capillary entry pressure before and after nanofluid treatment are calculated. The results show that the organic acid-aged SA basalt substrates become intermediate-wet to CO ₂ -wet under reservoir pressure and temperature conditions. When treated with SiO ₂ nanofluids, however, the SA basalt substrates become weakly water-wet, and the optimum performance is observed at an SiO ₂ nanofluid concentration of 0.1 wt%. At 323 K and 20 MPa, the CO ₂ column height corresponding to the capillary entry pressure increases from -957 m for the organic-aged SA basalt to 6253 m for the 0.1 wt% nano-treated SA basalt. The results suggest that the CO ₂ containment security of organic-acid-contaminated SA basalt can be enhanced by SiO ₂ nanofluid treatment. Thus, the results of this study may play a significant role in assessing the trapping of CO ₂ in SA basaltic formations.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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