Application Research of TA-LDHs Intercalated Retarder Modified Ultra-Fine Cement in Casing Damage Remediation of CCUS Injection-Production Wells

For casing damage phenomena including casing corrosion, rupture, and seal failure that frequently occur in carbon capture, utilization, and storage (CCUS) injection-production wells under long-term gas injection and pressure fluctuations, combined with the characteristics of ultra-fine cement slurry such as concentrated hydration heat release and vulnerability to acidic environment corrosion, this study synthesized tartaric acid-intercalated Mg-Al layered double hydroxides (TA-LDHs) through ion-exchange reaction as a functional retarder, and focused on screening the water–cement ratio as well as the dosages of fluid loss additive and dispersant suitable for CCUS working conditions. The results demonstrate that at a water–cement ratio of 0.7 with 1.5% fluid loss additive TSJ-1, 0.4% dispersant FSJ-1, and 0.2% TA-LDHs retarder, the cement slurry presents excellent rheological properties, a short thickening transition time, and remarkable resistance to acidic environment erosion. Plugging performance evaluations reveal that under simulated formation water conditions, the system maintains a breakthrough pressure gradient above 90.5 MPa·m−1 and a plugging efficiency of more than 99%, and after 30 days of curing, its compressive strength reaches 29 MPa while the plugging efficiency is improved to 99.37%. Furthermore, after exposure to CO2-saturated simulated formation brine at 80 °C and 20 MPa for 30 days, the TA-LDHs-modified cement exhibited a compressive strength of 27.0 MPa and a strength retention of 93.1%, while its permeability increased by only 23.1%. In comparison, the compressive strength retention of the control cement was 80.8%, and its permeability increased by 138.5%. These results indicate that the TA-LDHs-modified ultra-fine cement possesses favorable plugging performance and improved resistance to CO2-induced degradation, showing potential for casing damage remediation in CCUS wells.