Study on the carbonation resistance of oil well cement with LDH-whisker composites

With the intensified development of acid gas reservoirs and the rapid increase in the number of Carbon Capture, Utilization, and Storage (CCUS) wells, cement sheaths are increasingly exposed to CO 2 -induced corrosion, leading to sealing failure and a shortened service life of oil and gas wells. This, in turn, results in significant economic losses. Based on the corrosion mechanisms associated with CO 2 , this study investigates the corrosion resistance performance of a single additive system incorporating Magnesium-Aluminum layered double hydroxides (Mg-Al LDH), as well as a composite additive system combining Mg-Al LDH with calcium-based whiskers. The performance of the cement slurry system with added anti-corrosion additives was tested, and the performance and structural characterization of the hydration products after carbonation were analyzed using XRD, SEM, MIP, BSE, and TG to elucidate the action mechanism. The study shows that after 56 days of corrosion curing under a CO 2 partial pressure of 15 MPa, the compressive strength of cement paste with 2% Mg-Al LDH and 1% calcium-based whiskers increased by 8.01 MPa compared to the pure cement system, and the strength degradation rate decreased by 8.85%. The calcium-based whiskers improve the system's density by utilizing the filling effect of their ultra-fine particle structure. At the same time, Mg-Al LDH acts as a heterogeneous nucleation site, promoting the formation of C-(A)-S-H and enhancing the cement paste's resistance to CO 2 corrosion. These mechanisms are significant for improving the durability of cement-based materials.