Study on the integrated evaluation method for self-healing of cement sheath

The long-term cement sheath sealing integrity is essential for maintaining zonal isolation during oil and gas well operations. However, conventional self-healing evaluation methods often involve specimen transfer among separate curing, damage-generation, healing, and testing devices, which may disturb the original leakage pathway and affect the measured recovery. In this study, an integrated evaluation method was developed to perform cement curing, pressure-induced leakage pathway generation, gas-triggered healing, and sealing evaluation on the same specimen. Three operational indicators were employed: fracture-creation pressure-bearing capacity, flow-based self-healing efficiency, and secondary self-healing efficiency. At 90°C and a slurry density of 1.90 g/cm³, the conventional cement slurry showed no measurable sealing recovery within 72h. The expansive type system exhibited rapid recovery, reaching 88.24% at 12h and 84.12% at 72h, whereas the dissolution-viscosity type system increased progressively from 12.5% to 50.0%. In repeated damage-healing tests, the secondary self-healing efficiency of the two systems were 57.50% and 57.14%, respectively. Higher temperatures enhanced sealing recovery, and both systems approached approximately 90% after extended healing. The dissolution-viscosity type system also exhibited a higher initial fracture-creation pressure and lower initial gas flow rate. The proposed method enables continuous, time-resolved comparison of cement sheath sealing recovery while reducing specimen-transfer disturbance.