Comportamento da pasta de cimento classe G com adição de nanoalumina para aplicação em armazenamento geológico de carbono

Abstract

With the growing global concern over greenhouse gas emissions, the geological storage of carbon in depleted oil wells has emerged as a strategy to reduce CO2 emissions into the atmosphere. However, the durability of the materials used in these wells is a challenge due to degradation over time. In this context, this study investigates the behavior of Class G oil well cement pastes with the addition of nanoalumina (n-Al2O3), at contents of 0.5; 1; 1.5 and 2% by weight, under carbon capture and storage (CCS) conditions at 90 °C and 15 MPa, at curing ages of 21 and 90 days. The samples were characterized by compressive strength tests, scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), X-ray microtomography, thermogravimetric analysis (TGA), X-ray diffraction (XRD), and solid-state nuclear magnetic resonance (NMR) of 29Si and 27Al. The results demonstrated that the addition of the nanoparticle significantly influenced the evolution of the microstructure and mechanical properties of the cement pastes. SEM analysis revealed a denser and less porous microstructure in the pastes with the nanoparticle addition. XRD and FTIR characterization indicated that n-Al2O3 favored the reduction of CH peaks and the increase in C-S-H formation. Compressive strength increased by up to 24.3% (2% Al2O3) before CO2 exposure and by 8.1% (0.5% Al2O3) after exposure, compared to the reference sample. The 27Al NMR results indicated that aluminum is incorporated into the C-S-H chain. Additionally, the 29Si NMR results after 90 days showed a higher degree of hydration and an increase in the average C-S-H chain length. Overall, n-Al2O3 improves the properties of cement pastes, making them suitable for geological CO2 storage.