Laboratory Evaluation of Antileakage Performance against CO2 of Alkali-Activated Gel-Reinforced Cement for Carbon Capture, Utilization, and Storage

Summary With the rise of carbon capture, utilization, and storage (CCUS) technology, the demand for CO2 flooding and underground CO2 storage is increasing. However, CO2 leakage during injection and long-term storage is a non-negligible risk. Among these, the chemical damage and mechanical failure due to the carbonation corrosion of the cement sheath in oil wells pose a significant threat to CO2 geological storage. Thus, enhancing the corrosion resistance of the cement sheath under high-pressure CO2 conditions is a crucial technical issue. In this study, an alkali-activated gel was added to G-grade oilwell cement slurry. The performance of the reinforced cement was evaluated through high-pressure dry-phase and wet-phase CO2 corrosion experiments combined with mechanical testing, permeability analysis, and microscopic characterization. Results show that, compared with the control sample, the cement stone with 0.1% deep penetrating sealer (DPS, alkali-activated gel) additive exhibits a 40.35% increase in compressive strength, a 60.64% reduction in permeability, and a 38.19% reduction in corrosion depth. X-ray diffraction (XRD) and nuclear magnetic resonance (NMR) results revealed that the DPS solution reacted with Ca(OH)2 in the cement, generating more calcium silicate hydrate (C-S-H) gel and delaying the cement carbonation process. This finding offers new experimental evidence for the application of alkali-activated reinforced cement systems in CCUS cementing engineering and paves the way for future development and use.