Restoration of annular zonal isolation using localized casing expansion (LCE) technology: evaluation of Local Expander tool performance for treatment of dual cemented casing sections

Vollständiger Abstract

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Abstract Ensuring long-term zonal isolation integrity along wells is essential for sustainable subsurface applications such as geothermal energy production, hydrogen storage, and carbon sequestration. When cemented wellbore annuli become transmissive, effective remediation methods are required. Localized Casing Expansion (LCE) is an emerging technique that restores sealing by plastically deforming the casing, compressing the annulus, and closing defects in the cement sheath. While LCE has demonstrated effectiveness in single-annulus systems, its performance in dual-annulus configurations remains uncertain, as deformation of the inner casing must be transmitted through nested annuli to affect the outer cement sheath. In this study, two full-scale test vessels with artificially induced microannuli (yielding ~0.1 Darcy effective annulus permeability) were constructed to evaluate this mechanism. LCE-treatment eliminated detectable seepage in the inner annuli and reduced permeability of the outer annuli by 97–99%. Subsequent “high-power” LCE-treatments, applied under extended tool operating conditions, further improved sealing performance, achieving permeabilities in the microdarcy range. These results provide the first full-scale experimental demonstration that LCE can restore zonal isolation across dual cemented annuli. The findings indicate that load transfer through nested cement sheaths is sufficient to achieve meaningful sealing improvement, supporting LCE as a scalable, rigless solution for multi-annulus well remediation.